text:
Is buying older power plants than what you have disallowed?
In a recent game of Power Grid, someone we play with regularly insisted on a rule that you're not allowed to purchase a "lower" technology power plant than you already have.  e.g. if you have 13,17,25 as your power plants, you can't buy 24 or lower if they come up.
He also insisted that if a player didn't win their power plant auction that the market isn't refreshed before they got another chance to bid.  e.g. Player A bids cost, player B bids cost + 1 and player A decides not to bid higher.  In this scenario player A only gets to choose from the 3 remaining plants next.
The question: are these official rules?  I have scanned the rule book and didn't see either, but may have missed them... I also found them quite hard to work with.

someone we play with regularly insisted on a rule that you're not allowed to purchase a "lower" technology power plant than you already have. e.g. if you have 13,17,25 as your power plants, you can't buy 24 or lower if they come up.

Incorrect.  You can buy any power plant that is in the market (the lowest four numbered plants).

if a player didn't win their power plant auction that the market isn't refreshed before they got another chance to bid.

Incorrect.  After any power plant is purchased or destroyed, the market is immediately refreshed and realigned.
http://riograndegames.com/uploads/Game/Game_5_gameRules.pdf
Page 3, section 2b (this is retyped and not copy-pasted, so there may be typos)

The player chooses one power plant from the actual market (top row) and then makes a bid to purchase it.  [...] He pays his highest bid to the bank and takes the power plant.  Players then immediately draw a new card to replace the card sold and place the new card in the market.

Brilliant, thanks.  I didn't think they were "real" rules but before I argue the toss next time wanted to get an answer from someone more familiar than I.


text:
Do creatures summoned by a Planeswalker have summoning sickness?
Elspeth, Sun's Champion has a loyalty ability which says:

Place three 1/1 white soldier creature tokens onto the battlefield.

When this ability is activated, do these soldiers have summoning sickness? I ask because Elspeth herself does not have summoning sickness when placed onto the battlefield.

Yes, they'll have summoning sickness. Every creature experiences summoning sickness, without exception, unless something says it doesn't, such as having Haste. Elspeth herself doesn't experience Summoning Sickness because she isn't a creature - she's a  planeswalker.
For an example of a Planeswalker that places creatures which do have Haste, see Xenagos, the Reveler.
Summoning sickness comes from rule 302.6:

302.6. A creatures activated ability with the tap symbol or the untap symbol in its activation cost cant be activated unless the creature has been under its controllers control continuously since his or her most recent turn began. A creature cant attack unless it has been under its controllers control continuously since his or her most recent turn began. This rule is informally called the "summoning sickness" rule.

In short: Summoning Sickness means a creature can't attack, or activate abilities with a tap or untap symbol in their cost, until they've been under your control since your untap step.
If a permanent on the battlefield is turned into a creature — e.g. you transform your Mutavault — it will suddenly start being affected by summoning sickness, if you haven't controlled that permanent since the beginning of your turn. For this reason, an alternate way to describe it is that everything has summoning sickness, but it only affects things if they're creatures.
Creatures affected by summoning sickness can still be tapped by other things, though. You can cast Devout Invocation, for instance, and tap a creature that you only just summoned.

As a side note, if Elspeth were to somehow become a creature (by a combination of Mycosynth Lattice and March of the Machines, for example), she would have summoning sickness. You would still be able to activate her abilities, because they don't require tapping, but you wouldn't be able to attack with her the turn you played her.

I usually try to explain to new players that everything has summoning sickness, but it only affects creatures. The Summoning Sickness video from the Judge's Corner on Youtube also explains it like this.

source: Stack Exchange

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sort: votes


text:
Does Prophet of Kruphix apply to Planeswalker abilities that create creatures?
The Prophet of Kruphix has the ability

You may cast creature cards as if they had flash.

Does this apply to the Loyalty ability

Put three 1/1 white soldier creature tokens onto the battlefield

of the Planeswalker Elspeth, Sun's Champion?

No, there's no overlap here at all, for two reasons.

Elspeth doesn't involve casting creature cards. What goes on there has nothing to do with the process of casting creature cards.
Even if it did, you don't have anything that lets you use Planeswalker loyalty abilities on other peoples' turns.

Casting a creature card is the process you go through to put Prophet of Kruphix on the battlefield in the first place:

You take it from your hand.
You pay its costs.
The spell goes on the stack. (It's a creature spell, because the card has the creature type.)

That's the casting part. Hopefully, it doesn't get countered. When the spell resolves, the creature lands on the battlefield.
Sometimes it's a little different: a card with Flashback (Ancient Grudge) can be cast from your graveyard rather than your hand. A card with Cipher (Paranoid Delusions) has a free copy cast of it sometimes. But the process is still the same: the creature, or the spell, goes on the stack.
Elspeth's ability isn't the same thing. It's a loyalty ability and it's that ability that goes on the stack. When it resolves, it puts some creature tokens on the battlefield. The ability is used, but a spell isn't cast. Also, the tokens may get represented by physical cards, but they're still tokens and don't count as cards.

Okay, understood. I got both of these cards in booster packs, trying to maximize what I can do with them. Thanks!

You got a couple of really nice cards. Congrats, and have fun.

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text:
Cards granting emblems
Are there any spells (sorceries, instants) that grant emblems? The only way to get an emblem that I've seen so far is for a planeswalker's ability to grant an emblem. I wonder if there is any other spell that can be cast to receive an emblem.

No, not at this time.

o:emblem means the Oracle text (rules text) of the card must include the word "Emblem".
-t:planeswalker means the card must not have the type "Planeswalker".

The 18 cards that do mention "Emblem" are all Planeswalkers.

I'll take that answer, but how do you know?

Did you follow the link?

This answer is technically still accurate, but could probably use an update to account for new cards (found at the links you already provide). The second link lists several non-planeswalker cards now, but they're all DFCs with planeswalkers on their back that actually create the emblems. The first link now goes to Teferi's Talent, which is an enchantment that defines an emblem but only lets a planeswalker create it; a near miss in my opinion.

In addition to that, the new keyword action "the Ring tempts you" creates an emblem called The Ring. As a result, a number of non-planeswalker cards now create that emblem.

While not strictly speaking emblems, there are non-Planeswalker cards which create effects with durations of "for the rest of the game," which is the original wording for Elspeth, Knight Errant (before she was errataed to have an emblem).
Cyclopean Tomb removes mire counters that it put onto a land each turn for the rest of the game after it leaves the battlefield.
Praetor's Counsel gives you no maximum hand size for the rest of the game.
Stigma Lasher prevents a player from gaining life for the rest of the game.
The Epic ability from Saviors of Kamigawa prevents you from casting additional spells for the rest of the game. (Enduring Ideal, Eternal Dominion, Neverending Torment, Undying Flames, Endless Swarm)

Planeswalkers are the only sources of emblems
Mark Rosewater, the Head Designer for Magic, has said on his Tumblr blog that

We have chosen to make emblems a planeswalker-only thing.

That is one of many answers Mark has given regarding emblems, stretching at least as far back as 2011, and continuing to the present day, where Ascend (which is a "for the rest of the game" mechanic which could have been designed using emblems) has prompted questions about the issue again.  All of them say basically the same thing.
WotC could, of course, change this decision and decide to let non-Planeswalker cards create emblems.  But they have so far shown no signs of being interested in doing so.
That said, until any cards are printed which interact with emblems in any way, effects which last "for the rest of the game" are functionally equivalent to emblems, and those do exist on a number of different card types.  The distinction that makes one of these effects an emblem has far more flavor significance than it does mechanical significance.
Special mention goes to Obsidian Fireheart, the card that held the title for "Greatest Reminder Text" ("The land continues to burn after Obsidian Fireheart has left the battlefield") until the Unstable card Gimme Five stole that title with "Offer high fives.  Don't hit people."

No longer accurate - "The Ring" is an emblem and is granted by the "The Ring Tempts You" mechanic that appears on non-planeswalker cards

As of today (Dec 24, 2014) there are 18 cards with Oracle wording that gives an emblem. As you can see, they are all Planeswalkers.
(source: this search here - I've cleaned up some un-necessary details for readability)

Name
Type

Ajani Steadfast
Planeswalker — Ajani

Dack Fayden
Planeswalker — Dack

Daretti, Scrap Savant
Planeswalker — Daretti

Domri Rade
Planeswalker — Domri

Elspeth, Knight-Errant
Planeswalker — Elspeth

Elspeth, Sun's Champion
Planeswalker — Elspeth

Garruk, Apex Predator
Planeswalker — Garruk

Garruk, Caller of Beasts
Planeswalker — Garruk

Kiora, the Crashing Wave
Planeswalker — Kiora

Koth of the Hammer
Planeswalker — Koth

Liliana of the Dark Realms
Planeswalker — Liliana

Ob Nixilis of the Black Oath
Planeswalker — Nixilis

Sarkhan, the Dragonspeaker
Planeswalker — Sarkhan

Sorin, Lord of Innistrad
Planeswalker — Sorin

Sorin, Solemn Visitor
Planeswalker — Sorin

Tamiyo, the Moon Sage
Planeswalker — Tamiyo

Teferi, Temporal Archmage
Planeswalker — Teferi

Venser, the Sojourner
Planeswalker — Venser

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text:
What planeswalker cards can be used as commanders in the Commander format?
Can any Planeswalker be used as a Commander, or just the ones that say "XXXX can be your Commander" on the card?
(N.B. This question has nothing to do with the Brawl format.)

Currently (in November 2018) there are the following sets of planeswalkers that you can use for your commanders:

The five double-faced transforming planeswalkers from Magic Origins. This is because they're a Legendary Creature on their front face, which is what the Commander rules are looking for.
Nicol Bolas, the Ravager, also a double faced card that starts as a Legendary Creature.
Three sets of planeswalkers which say “(This card) can be your commander”:

The five mono-color planeswalkers from Commander 2014
The four multi-color planeswalkers from Commander 2018
Rowan and Will Kenrith from Battlebond

These latter sets of commanders are still not legendary creatures, but golden rule 101.1 lets them make themselves exceptions.

101.1. Whenever a card's text directly contradicts these rules, the card takes precedence. The card overrides only the rule that applies to that specific situation. The only exception is that a player can concede the game at any time (see rule 104.3a).

This is like how the Commander 2016 Partner commanders also get to make themselves exceptions from the usual Commander rules.

As of Ixalan, all planeswalkers are going to be Legendary Planeswalkers, including retroactively. You still won't be able to use them for your commanders because they won't be Legendary Creatures. Sheldon of the Commander Rules Committee has said there aren't plans to allow all planeswalkers (posted 28 August 2017, in response to an inquiry about planeswalkers becoming legendary):

No, PWs will not be allowable as commanders unless a card specifically says that it can--so no change.

(This is like how they're not allowing Legendary Artifacts or Legendary Enchantments — it's not about being legendary, it's about being a Legendary Creature.)
House ruling exceptions for fun
That said, Commander is intended to be a format played casually for fun with friends — the official EDH site's Philosophy section says as much. That same section explicitly encourages people to make exceptions or changes to the rules for local play if it's fun. Unless you're in some kind of official sanctioned event, adherence to the Commander rules is only necessary insofaras you and your friends find it fun. If you and your friends want to allow Planeswalkers as commanders, by all means, talk about it and create such a rule between yourselves, and then make a deck with a Planeswalker as a commander.
Where are the rules for planeswalker not being commanders?
There's two sources of Commander rules you can check to verify the absence of Planeswalkers in general being allowed:

The official Commander/EDH site's rules, which say the following:

Players must choose a legendary creature as the "Commander" for their deck.

No mention of Planeswalkers.
The MTG Comprehensive Rules, probably easiest found on the MTG Wiki Commander format article, which also includes some community commentary and explanation. Those rules say:

903.1. In the Commander variant, each deck is led by a legendary creature designated as that deck’s commander. The Commander variant was created and popularized by fans; an independent rules committee maintains additional resources at MTGCommander.net. The Commander variant uses all the normal rules for a Magic game, with the following additions.

(Notably they defer to the site I linked in point 1.)

Thanks. I'm sorry to hear that, but at least I haven't already invested in a card I can't use.

@MPW: Keep in mind that the Commander format isn't used in any official tournaments (or, at least, the vast majority of Commander play is outside of tournaments), and so you'll always be playing it in a casual context with a group of (hopefully) friends.  These friends may choose to allow you to use any planeswalker as your Commander; house rules like this are even explicitly encouraged in the official Commander rules, under "Philosophy": "House rules or 'fair play' exceptions are always encouraged if they result in more fun for the local community."

@jwodder Good point! I was thinking of pointing something like this out, and I guess I should! I'll edit some of those details in too.

@jwodder: ok, cool. I'll mention it to my group, maybe I can do it after all. Thanks!

(Weee! A situation where 101.1 actually applies! Usually, when someone mentions 101.1, it's not actually applicable. This is not one of those times.)

Want to add a note about the transform planeswalkers from Magic Origins? We got a question-as-answer asking about that.

Another thing to keep an eye on is the recent changes to planeswalkers uniqueness rule, has sparked some discussion on possibly changing the rules to allow any planeswalker to be a commander.

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text:
Can you sacrifice a creature that's in the middle of an attack?
Earlier tonight, I was playing magic. My opponent had a card out that allowed him to place a 2/2 goblin token on the board for every creature that made an attack. He also had one out that allowed him to sacrifice one of his creatures and destroy any nonland permanent.
He declared an attack with one of the goblin tokens, thus placing another goblin token on the board. He then sacrificed the attacking token before it attacked and my blocker destroyed it.
I'm new to the game, but it seems to me that if he sacrificed it prior to its attack, it shouldn't have counted as an attack. So he couldn't have placed the new token on the board. Am I wrong?

Could you name the cards being used here? That would let us more concretely discuss the situation. Namely, the card that let your opponent place goblins, and the card used to sacrifice one.

Seems likely that OP is talking about a card with an attach trigger (like Brimaz), in which case it is useful to distinguish between triggered abilities that are "whenever ~ attacks" vs. "whenever ~ deals combat damage to a player".

Your opponent could have declared that token as an attacker, then sacrificed it before actual combat damage happened. It would have counted as attacking — at least until it was sacrificed — but it wouldn't have actually done any combat damage to its blocker.
The combat phase works like this:

Beginning of Combat Step

Nothing has happened yet, but you're considered to be inside the combat phase. Players can cast spells and use abilities.

Declare Attackers Step

The active player may declare which of their creatures are attacking.
Those attacking creatures get tapped. They're now considered to be Attacking for the rest of the combat phase, even if something untaps them somehow.
Players may now cast spells and use abilities before moving on.

Declare Blockers Step

The inactive player may declare which of their creatures are blocking.
The inactive player assigns the blocking creatures among the attackers. These creatures are now considered Blocking for the remainder of combat, even if something taps them somehow. Any attacker assigned a blocking creature is now considered Blocked for the remainder of combat, even if its blocker disappears, and will not deal combat damage to you personally (unless it has trample, or something else that lets it do that).
Players may now cast spells and use abilities again before moving on.

Combat damage happens.

Any attacking creatures still alive and present at this point attack their blockers and/or the opposing player/planeswalker/etc.
  Nobody can cast spells during this process.

Combat finishes, the board gets cleaned up (dead creatures removed, etc).

It sounds like the Goblin in question was given a blocker during the Declare Blockers step. At that point, the other player does have the opportunity use an ability to sacrifice the goblin, and if the goblin is doomed to die, that's probably a good choice.
However, once combat damage happens, that sacrificed goblin won't be around anymore. You say this:

I'm new to the game, but it seems to me that if he sacrificed it prior to its attack, it shouldn't have counted as an attack.

It will have counted as attacking, but since it's dead by the combat damage step, it's gone and won't actually be there to do anything. Your blocker won't take damage from the goblin, for instance - the goblin will be dead and gone.
(There was a time in the past when you could cast spells and use abilities during combat damage, so that the goblin could deal combat damage and get sacrificed too, but that was weird and got removed from the rules a few years ago in M10.)

Has it already been 5 years!

+1 for the last parenthetical. Big rule changes like this one are super tricky, especially in a population where people may play for years without ever knowing about the change unless they play competitively.


text:
Do you replace tokens moved to the Trade Route mat?
With Trade Route in play, do you replace the coins on the victory cards after the first card is purchased?
Example: I buy a Duchy and move the coin to the Trade Route mat.  Do I put another coin token on the remaining stack of Duchies? Or is four the maximum number of coins on the Trade Route mat?

You do not replace the coin tokens. So with Colonies in the game, and no other extra victory cards, yes, four is the maximum number of coins on the mat. Remember that there potentially are other victory cards among the kingdom cards in the game, though, depending on what expansions you're playing with - like Gardens from the base game, and many others.
Why? Because the card doesn't say to. If you're ever having trouble with Dominion rules, just read the card carefully, and do exactly what it says in the order it says.

You do not replace them, but four is not the maximum number of coins: the kingdom may include victory cards like Harem, Gardens, or Feodum.

Trade Route tokens are never replaced.  They're either on the Victory cards or on the Trade Route mat.  Remember that if you gain a card, you also transfer the token over to the mat.  Last but not least, each Victory card, whether it's a starter card (e.g. Estate, Duchy, Province, Colony) or Kingdom card (e.g. Garden, Fairground, etc.) starts off with a token on it.


text:
When does Heroic trigger?
Suppose Player 1 controls a Favored Hoplite and casts Ordeal of Heliod targeting it. In response, player 2 casts Magma Jet on the Favored Hoplite.
Does the Heroic trigger from Ordeal of Heliod happen before Magma Jet, thus saving Favored Hoplite? Or does Magma Jet kill Favored Hoplite, with Ordeal of Heliod no longer having a valid target?

Favored Hoplite won't be saved. Ordeal of Heliod will have no valid target, will be considered countered, and will be sent to Player 1's graveyard.
When do Heroic abilities trigger?
Heroic abilities always follow this format:

Heroic — Whenever you cast a spell that targets {this card}, {do something special}

They trigger right after a spell is cast. A spell is considered cast when you place it on the stack, having paid its costs, chosen its target, and so on. This is the point when you and other players can put other spells and abilities on the stack to respond to that spell. It's also before the spell resolves. (Tangentially: even if a spell gets countered, that doesn't change that it was considered cast at some point. It just doesn't get to resolve.)
So you cast a spell targeting your Favored Hoplite, triggering its ability, which goes on the stack on top of the spell. The Heroic ability resolves before the spell does:

Ordeal of Heliod (bottom)
Favored Hoplite's Heroic ability

However, these haven't resolved yet. At this point, before either resolves, you and the other players have an opportunity to place other spells and abilities on the stack. If you're confused about how the stack works, check this question: In plain English, how does casting spells and using creature abilities work with the stack and priority?
What happens in this scenario?
In this case, your opponent may immediately cast Magma Jet (since it's an Instant) before either the Heroic ability or Ordeal of Heliod have a chance to resolve. That would make the stack look like this:

Ordeal of Heliod (bottom)
Favored Hoplite's Heroic ability
Magma Jet

Magma Jet will resolve first and kill your Favored Hoplite before the Heroic ability or Ordeal of Heliod get to do anything about it. You'll need to find another way to save it. That could include casting any instant targeting Favored Hoplite, which will trigger its Heroic ability again - and that one will resolve before Magma Jet and save it.

Might be worth mentioning that after Magma Jet is cast, he can cast any instant that targets the favored hoplite, which would then trigger another heroic which would resolve first and save it.

Good point - added that at the end

Could you clarify for bestow? Since if the target of a bestow disappears before the aura resolves, a creature ETB instead, so that is resolution. With an Akroan Crusader, would I get a token? I can ask this as a new question if you like.

@MattEllen I think that's worth asking as a separate question, yeah - it's beyond the scope of this one.

When in doubt, build an actual stack. Physically use your hands as placeholders for triggers. If the stack is too large, find pieces of paper and write down the name of what triggered. You don't have to be a programmer to build a stack out of of paper.
You cast Ordeal. It goes on top of the stack. Casting Ordeal triggers heroic. The trigger goes on top of the stack. You pass priority. Your opponent casts Magma Jet. It goes on top of the stack.
Now your stack looks like:

Magma Jet (TOP)
Heroic Trigger (MIDDLE)
Ordeal (BOTTOM)

You both let the stack resolve at this point.
The top of the stack resolves. Magma Jet kills your guy. Next, the top of the stack resolves. The heroic trigger has nothing to put a counter on anymore, so it doesn't do anything. Finally, the top of the stack tries to resolve, but Ordeal has no legal target anymore, and so it gets countered by game rules.

authors: Виктор Мандзюк


text:
Stalling/Slow Play and Control
As a control player, there are times where it takes a while to resolve the first game, and there are many times where I'm up a game. Are there any rulings against stonewalling the opponent and not taking any steps to end the game while playing at a reasonable pace? I feel prompted to ask this in light of Channel Fireball's article: Silvestri Says – It’s Time to Stamp Out Slow Play

No, there is no rule against playing so that the game as a whole progresses slowly, as long as you take all of your actions in a timely manner. The official tournament rules describe slow play (in section 5.5) as

Players must take their turns in a timely fashion regardless of the complexity of the play situation and adhere to time limits specified for the tournament. Players must maintain a pace to allow the match to be finished in the announced time limit. Stalling is not acceptable. Players may ask a judge to watch their game for slow play; such a request will be granted if feasible.

Note that this rule is primarily concerned with turn length and the pace of play. Stalling in this case means not taking any action or passing, such as by staring at your hand without actually playing anything on your turn.
If this seems a little ambiguous, the Competitive REL infraction procedure guide describes slow play more simply (in section 3.3) as

A player takes longer than is reasonably required to complete game actions... It is also slow play if a player continues to execute a loop without being able to provide an exact number of iterations and the expected resulting game state.

As long as you are completing game actions and turns in a timely manner, you won't break this rule.


text:
Can I activate a tap ability multiple times, though on different turns?
I have a card named Alloy Myr. It's an artifact creature with the ability

{T}: Add one mana of any color to your mana pool.

Can this ability be used multiple times, but in different turns of course?

Yes, you can use that ability once a turn (usually), but not the turn it entered the battlefield. The ability you describe is an activated ability, where the cost is tapping the creature and the effect is adding one mana to your mana pool. You can only pay the cost (by tapping) when a creature is untapped, so you can't use the ability multiple times in a row.
To tap a permanent, you turn it sideways. At the beginning of each of your turns, you untap all of your permanents, so generally you can use abilities that require you to tap the permanent once per turn. There are also effects that can untap permanents (e.g. Twiddle), so if you use one of those you can activate the ability again.
Creatures have summoning sickness. This means that you cannot tap the creature to pay an activated ability's cost or attack with it unless you controlled it since the beginning of your turn. So you can't use this particular creature's ability until the turn after you play it.
To summarize:

You can use a 'tap' ability on a permanent as long as:

The permanent is on the battlefield and currently untapped, AND

The permanent is not being prevented from tapping, either by summoning sickness or by another ability (e.g. 'cannot use activated abilities')

All permanents untap automatically during your untap step (at the start of your turn) unless something has prevented them from doing so

If a permanent has Haste, it ignores summoning sickness, and therefore can be tapped on the turn it enters the battlefield (unless otherwise prevented from doing so as per above)

Hope you don't mind - I added a summary to your post, to clarify some of its points.

What does that last point mean? All permanents untap before their controller's upkeep step; that's what the untap step is.

Little note here: every permanent without haste has summoning sickness, but only creatures are affected by it. So for example: a non-creature artifact with a tap ability can be used the turn it is cast. Also for example, with 'Erebos, God of the Dead', if the devotion requirement for it to be a creature is not met, it can draw a card the turn it is cast onto the battlefield.

Actually, it makes more sense to say that only creatures have summoning sickness. The exact rule is 302.6: "A creature's activated ability with the tap symbol or the untap symbol in its activation cost can't be activated unless the creature has been under its controller's control continuously since his or her most recent turn began. A creature can't attack unless it has been under its controller's control continuously since his or her most recent turn began."


text:
Do +1/+1 counters accumulate?
This might be quite basic. I am just a beginner and searched through the web and the rule book and couldn't find the answer.
For instance, Ajani's Pridemate lets you,

Whenever you gain life, you may put a +1/+1 counter on Ajani's
  Pridemate. (For example, if an effect causes you to gain 3 life, you
  may put one +1/+1 counter on this creature.)

Then does that counter(s) last across turns and accumulate making Ajani's Pridemate much stronger creature as the game progresses until it dies? Say, you have a staff that lets you

Whenever you cast a black spell or a Swamp enters the battlefield under your control,
  you gain 1 life.

Every turn you put down a Swamp you gain 1 life and hence Ajani's Pridemate gets another +1/+1 counter. It can even become like 2/2 + 1000*(+1/+1 counter) making it 1002/1002. Am I right?

I remember playing grimgrin with rooftop storm and ghoul raiser for infinite +1/+1 counter loop :).

Yes it can. Every instance if lifegain grants another +1/+1 counter. So if you play 10 Swamps, you have 10 instances of lifegain, which grants 10 +1/+1 counters. If you have a creature with lifelink which deals damage, you gain life, so Ajani's Pridemate gets a +1/+1 counter. There is no limit to the amount of +1/+1 counters it can get.

In Magic things stay where they are unless instructed to move/remove them. This why effects that grant temporary effects are worded with "until end of turn".

611.2a A continuous effect generated by the resolution of a spell or ability lasts as long as stated by the spell or ability creating it (such as “until end of turn”). If no duration is stated, it lasts until the end of the game.

(thanks ikegami for the rule #)
Here's a specific rule dealing with your question:

118.9. Some triggered abilities are written, "Whenever [a player] gains life, . . . ." Such abilities are treated as though they are written, "Whenever a source causes [a player] to gain life, . . . ." If a player gains 0 life, no life gain event has occurred, and these abilities won't trigger.
Example: A player controls Ajani's Pridemate, which reads "Whenever you gain life, you may put a +1/+1 counter on Ajani's Pridemate," and two creatures with lifelink. The creatures with lifelink deal combat damage simultaneously. Ajani's Pridemate's ability triggers twice.

Note that the card doesn't even have to continue to be affected by the counters in order for them to stay:
See Raging Ravine

Any +1/+1 counters put on Raging Ravine remain on it even after it stops being a creature. They'll have no effect until it becomes a creature again.

And the fact that they can accumulate and stick around is precisely why you want (physical) counters - it'd be hard to keep track of otherwise.

Yes. It keeps them because nothing in your scenario removes them.

You didn't mention any abilities removing counters, so the only possible thing that could be removing counters are the rules.
There are only three instances when counters are removed from objects by the rules, and none of them are relevant to the current situation.

Dealing damage to a Planeswalker removes loyalty counters.
SBAs cancel out +1/+1 and -1/-1 counter pairs by removing them.
SBAs remove extra counters when a permanent has a limit to how many of a given kind of counters it can have.

That's it. Counters are never removed from objects except in those circumstances or by abilities that instruct you to move or remove them[1].
Under normal circumstances, a counter are never removed from the object on which it is paced; it stays on the object until the object ceases to exist (at which point they cease to exist too).

121.2. Counters on an object are not retained if that object moves from one zone to another. The counters are not “removed”; they simply cease to exist. See rule 400.7.

This includes three keyword abilities that remove counters:

Fading (fade counter)
Suspend (time counter)
Vanishing (time counter)


text:
Can explorers choose not to move?
Can explorers choose not to move? So instead of rolling dice or playing an action can a survivor skip their own turn so they don't leave a room? One example would be to stay in the mystic elevator and then each turn use the mystic elevator to travel around the house.

You should break this up into separate questions for better answers

I've removed your second and third questions. They don't seem intrinsically related to the one I've left behind, and should be asked separately in their own questions. You can still retrieve their content in your revision history, which you can access by clicking the 'edited X time ago' link at the bottom center of your post.

Mind you, the second question about being able to not move monsters may be related, if you believe the same rules may be involved. (I don't play this game.) If it seems intrinsically related - i.e. makes no sense to answer just one and not the other here - add it back. Otherwise, you are requiring people to answer two unrelated questions, which mainly just cheats you out of a good answer if someone knows the answer to one but not the answer to the other.

Yes, you can choose not to move. The rules on movement state:

Moving
On your explorer’s turn, you can move up to number of spaces equal to your character’s
current Speed.

"Up to" includes 0 spaces.
Note that if you stay in the elevator for your entire turn, then the elevator will move again. From the FAQ:

Heroes must roll for their destination floor each time they enter the elevator, or at the end of each entire movement phase that they spend in the elevator without moving.


text:
What does 'play' mean in the context of Courser of Kruphix?
Definition of 'play' in mtg for spells indicates it is synonym of cast. On the other hand on Courser of Kruphix it seems to be constant ability. What does 'play' mean in Magic?

Courser of Kruphix uses the word "play" in two different ways. When it says

Play with the top card of your library revealed.

It means that you play the game with the top card of your library revealed. That ability is a static ability, so it is in effect for as long as the Courser of Kruphix is on the battlefield.
On the other hand, when it says

You may play the top card of your library if it's a land card.

That simply means that you can play lands on top of your library like your are normally able to do from your hand.

You should probably mention the thing where 'play' and 'cast' don't mean the same thing.

I don't see why it's relevant here. Courser of Kruphix says that you can play lands from the top of your library. This is the standard wording for the special action that you can perform once per turn to put a single land into play while the stack is empty during your main phase. Anything involving spells is irrelevant.

The asker thinks casting and playing are analogous and is confused why some cards say 'cast' but Courser says 'play'. That's all. This is a good answer even without that and I've already upvoted it, I just think this would be beneficial to mention.

The way I read the question, I think the asker's actual point of confusion was the distinction I explained in my answer. If they say that is not the case, I'll change my answer. Until then, I see no reason to change it.

fair enough then

That exactly answered my question! Thank you all! Great community!

I too think the distinction between cast and play would be important to note, since the question mentions that they appear to be synonymous.

The asker's confusion is about the difference between "play" as it's used in the first ability and "play" as in "play a card", which are completely separate things. In my opinion, adding in notes about the difference between casting spells and playing lands would be superfluous and would only distract from the distinction I'm trying to explain. If you want an answer that explains that difference, you are free to add your own, or upvote one of the existing answers that does so.

I think it deserves a special mention that the usual restrictions to playing lands still apply. Most notably, you can only play 1 land per turn, regardless of whether you played it from hand or from your library via Courser.

Guys, actually all the things you mention I found online, my confusion was because Courser say play (something) instead of play the game as murga explained. Then I checked what play meant :)

Play means two different things here. (It used to mean a lot more things; see the footnote at the end.)
The first ability's instruction to play with the top card of your library revealed just means that whilst you're playing the game, you should have the top card of your library revealed.
In the second ability ("You may play the top card ..."), "playing" a card is close to casting, but "playing" is a broader term that refers to something else in addition to casting. Playing a card refers to one of two things:

cast a card as a spell1, or
put a land onto the battlefield2, which doesn't use the stack or count as casting.

In particular, that means lands cannot be cast. They can only be played. So, Courser of Kruphix has to use the verb "play", as must anything that lets you put a land on the battlefield.
Compare this to Daxos of Meletis, who allows you to cast exiled cards — which means you can cast creatures, sorceries, instants, artifacts, and enchantments exiled by Daxos, but not lands.

Footnote: In cards printed before the Magic 2010 core set (released 2009), "play" meant other things, such as activating an ability, and the "cast" verb wasn't a thing. "Play" was pretty overloaded and confusing, so they made those usages obsolete in 2010 and added new concepts such as "casting" a spell and "activating" an ability.

When playing with Courser of Kruphix you will play with the top card of your library revealed (first ability).
If that revealed card happens to be a land you can then play it as if it was in your hand (can still only play the normal amount of lands each turn and you can only use it when you can normally play a land). This will gives you a couple of benefits.  First it lets you play a land if you don't have one in your hand (or chose not to play a land from your hand). Second it lets you get a land card out of the deck faster so you can get to more valuable cards. Third you get to gain life from the third ability.
So in short for this card "play" is treated like playing any other land on your turn
Here is the rulings on this card
http://gatherer.wizards.com/Pages/Card/Details.aspx?name=courser+of+kruphix

Yes, thank you, but some people keep reavealing their cards as long as courser is on battlefield, not only when they play (cast) it. Is it correct?

@xio As long as it is in play the top card of the deck will be revealed. It says to play with the top card of your library revealed.

Joe, just to make sure - when I checked definition of play in mtg it said it means to cast (except for lands). You cast a spell only once. Why in case of courser it means something else? Sorry if this is obvious/naive question.

@xio Look at dopperlgreener's answer for a better explanation.

Doppelganger answered a different question, my issue is consistence of magic keywords. To add to my confusion - the definition of 'play' from the rules: http://www.mtgsalvation.com/forums/magic-fundamentals/magic-rulings/magic-rulings-archives/291359-definition-of-play

@xio you will want to reread that. 701.11b To play a card means to play that card as a land or to cast that card as a spell, whichever is appropriate. Reading that it shows you have two options, play the card as a land or cast that card as a spell. If you look closer at the post it is only focusing on the casting part and not the playing land part. Also its always better to get the rules from the official site. http://media.wizards.com/images/magic/tcg/resources/rules/MagicCompRules_20140601.pdf

I don't mean to contradict for the sake of the discussion, I'm trying to figure this out. Is there any paragraph in the rules that suggests that to play a creature means to have it on the battlefield? Play is an action after all, not a status of the card...

@xio I think you need to take a look at the rules and the card you are asking about as all that is involved is the ability to play a land not a spell of any type from the top of your deck.

"Play with the top card of your library revealed" - ok simple: I play the courser. I reveal the card. Where does it say I reveal again next turn? :)

@xio the next turn if your top card is not revealed are you following the wording on the card or doing the opposite?

@xio I think that my answer can resolve your confusion.

Yes, Murgatroid, now I understand! Play the game, not play the card. Thanks guys!


text:
Two Headed Giant - do I gain life when my teammate gains life?
I'm playing Two-Headed Giant. I have Ajani's Pridemate, which has "Whenever you gain life...".
My teammate plays a card, that makes him gain life. As we share our life total, my life is also updated. Do I get to activate Pridemate's ability, when my teammate plays the card?

No, the Pridemate's ability doesn't trigger when your teammate gains life, because while your shared life total goes up it is not you gaining life.
Two-Headed Giant FAQ:

How does damage, loss of life, and gaining life work with the single life total for the team?
  Damage, loss of life, and gaining life happens to each player individually. The result is applied to the
  team’s shared life total.

810.9 in the comprehensive rules also states this.

You'd think the inverse would also be true, but Platinum Emperion is a funny card.

@HaoYe No, Platinum Emperion doesn't say you can't gain or lose life, it says your life total cannot change, your team mate gaining or losing life would change your life total, so since that can't happen, they can't gain or lose life either. If platinum Emperion had been worded to say you can't gain or lose life, then your ally could still cause your shared life total to change by gaining or losing life.

@Andrew, as rule says, if you can't gain life, your teammate can't gain life either. 810.9g If an effect says that a player can’t gain life, no player on that player’s team can gain life.


text:
Can you cast Hangarback Walker for X=0 and have it survive with Hardened Scales?
I'm building a deck with Hangarback Walker and Hardened Scales, and I was wondering if I could cast Hangarback for X=0, and it would activate Hardened Scales. Just a thought.

No, and for a very straightforward reason: Hardened Scales requires that at least one counter be placed on the creature before it adds any additional counters:

The key text here is 'If one or more'.  You're trying to put zero counters on the Hangarback Walker, and so Hardened Scales never processes.

Oh! Thank you, I guess I wasn't paying attention to the full ability.

Casting Hangarback Walker for 0, and it will enter the battlefield with zero +1/+1 counters. Since Hardened Scales requires "one or more" +1/+1 counters to be put on the permanent to trigger the replacement effect, Hardened Scales won't trigger. Hangarback Walker will Enter the Battlefield as a 0/0, and die due to state based Actions.
If you want to play Hangarback Walker for free, there are options:

Have a permanent in play that provides an anthem effect to your creatures of at least +0/+1.

Have it enter with a +1/+1 counter for Free. Zameck Guildmage or Master Biomancer.

Graft is not an option. Though the triggered effect of the creature will happen, state based actions will kill the 0/0 Hangarback Walker before the trigger can be placed on the stack.

While relevant, this is tangential and not actually answering the question.

Actually, he answered the question and then provided additional relevant "tangential" information.  Nothing wrong with that.  Going on a tangent myself, the answer wasn't any different than the preceding answer and the additional info should, IMHO, just have been added as a comment to the accepted answer.

The answer was initially solely tangential, to provide the effect desired by the Question. It was than edited to address the specific question asked.

I would just like to add to Steven Stadnicki's answer that even if it was a triggered ability that put counters on creatures when they enter the battlefield it still will not work.
State base actions would see a creature with zero toughness and it would be put in the graveyard before the triggered ability gets a chance to put any counters on it.
So lets say for instance instead of the scales you had Aquastrand Spider it still would not work for the reason I stated.

This is tangential, and doesn't actually answer the question.

Ability is triggered, but it isn't put on the stack.

Notice that Hardened Scales effect is not a triggered ability but a static replacement effect.


text:
Can opponents keep Jeskai Infiltrator under their control past the end of their turn if it was manifested?
So recently, when I was vsing a friend, they used Act of Treason on my Jeskai Infiltrator, then attacked me. I took the damage without blocking, then Jeskai and the top card of their library was exiled, shuffled, and manifested because of the second ability.
Reading other posts on this site, it seems that they would keep control of the manifested cards past the end of their turn, but it was never directly stated. So I just want some clarification on the rules of this card: do they get to keep it?

Could you clarify who the "we" and "they" are? Is your friend your opponent or your ally in this?

The "we" was the group I was playing with, and "friend" and "they" refers to my opponents.

Suggestion might be to change we and us to me and I, due to the possibility of it obfuscating the question, despite the answer being the same.

Yes, they will keep control of Jeskai Infiltrator. The card was exiled and then returned to the battlefield, so it is considered by the rules a new permanent with no relation to the card that Act of Treason was used on.

400.7. An object that moves from one zone to another becomes a new object with no memory of, or relation to, its previous existence. There are seven exceptions to this rule:

(none of the exceptions apply here).
Remember that everybody will know which of the face down cards is Jeskai Infiltrator, because who is the owner of a card is always known. There is a ruling in Jeskai Infiltrator that confirms this.

Thank you Pablo for the feedback. It was good to get this off my chest.

@Pablo Recommendation to add, although it's not directly necessary to correctly answer the question: When your opponent controls two manifested cards, and one of them is your opponent's, you have to inform them which one of them is theirs, even if you've shuffled them like Jeskai Infiltrator's effect.

@Waterseas I can't find any rule about that. Could you tell me where have you learned it?

@Pablo Unfortunately not certain what rule it is based on off-hand, however this is the appropriate ruling on the card: "11/24/2014: A card’s owner is public information at all times. If the two cards you exile are owned by different players (perhaps because you gained control of a Jeskai Infiltrator owned by your opponent), which card is which is no longer hidden from your opponent. That player will know which face-down creature he or she owns."


text:
What is this game with a 12x8 pegboard and 59 double sided pegs?
I was wondering if anyone knows what this game is.
It has 59(maybe missing 1) pegs that are red on one side and wood color on the other.
It is a 12 x 8 Pegboard Game.
There are no markings on the inside or outside and it folds like a briefcase.
Everything is made of wood except the handle, rubber feet, and latches.

The lack of markings is odd.  That seems to hint at home built.  Is that a possibility?

it is a possiblity

Are you so sure this is a game? It probably is, but it might not be.

A lot of games that originate from primitive cultures have hand-made wood-sculpted boards, are played with pretty pebbles from the local beach or forest, and have countless variations to the rules (like Mancala). To me this looks like one of those games, but from a somewhat more recent time.
There are infinitely many games you could play on this 12x8 board with double sided pieces, so I hope you have a game in mind but can't remember the title. Here's some guesses:

Five Stones is an old five-in-a-row game with some restrictions that is played on a 12x8 board, but it doesn't require double sided pieces.
City can be played on a 12x8 board, but it only requires 24 pieces to play.
It could be a Reversi/Othello variant, but those usually require as many pieces as positions on the board.
It could be a variation on Halma, although that doesn't require double sided pieces.
Konane has no board size defined in its rules, but requires as many pieces as positions on the board.

This is my best attempt at an answer to a question that I fear has no single answer. If you feel that these don't answer your question, please explain in your question why not, and I can delete this answer.

From your Konane link - you need as many pieces as positions. Also, there is no need for double sided pieces.

hum... Sounds like you eliminated all of your options

I've eliminated all of my single options, but it could be that this was made with the intention of allowing multiple games to be played on the same board.

Maybe if you listed listed some of those games, but you didn't even list games that exist. Rather than doing so, you listed speculative variants that use boards other than the one being asked about. But even that would be off-topic. The question isn't "what other games might be playable on board". I don't see how your noise is of any use at all. it just makes the question appear answered when you simply posted an off-topic comment.

SE is about improving questions and answers to provide the community's best, not any one person's

your pegboard looks like an earlier or a later edition of the plastic pegboard we have at the psychology museum. All pegs have two colors like yours. Among other things these and other pegboards were developed for testing dexterity in recruitment contexts and for testing and training eye-hand-coordination in neuropsychology. In neuropsychology it helps to assess neurological damages. Our version has the imprint "U.S.E.S. PEGBOARD". The abbreviation stands for "United States Employment Services". We got our exemplar donated though from the psychological laboratory of the Otto Wagner Hospital in Vienna, a psychiatry.

Wow!  Great answer.  (Hopefully the OP will be able to switch the accepted answer to this post.  Clearly, these are almost certainly the same thing.

I just did a Massachusetts state assessment test for the local Boston insulators union and this board was given to us to test manual dexterity. The test was broken down into two parts, each 30 seconds long. The first test we had to remove the pegs from one side to the next using both hands, the second test we had to flip the pegs one by one using only one hand.
By the way, the board we used looked exactly like the one posted by Sascha Frank

Although this is a non-standard board size, you could play Pente with this set.

As Bostonian previously stated....
I also took a mechanical aptitude and spacial relations test for a Boston Trades Union (Plumbers and Gasfitters) and as part of the Manual Dexterity portion of the exam, the U.S.E.S. Pegboard was used as the exam was proctored by MA Div. of Career Resources. (following the written portion of the exam)

This honestly looks like a simple connection game.  (See m,n,k games).

They used to have games like this at "folksy" restaurants when I was a kid. (The peg board resembles a cribbage-type board, although it's obviously not a cribbage board.)
It might be a proto-version of TwixT, without the strings.
Although it's possible it could be a jumping game, like Konane, I'd be surprised if it was for a jumping game like Halma or Checkers, where a checker board is pretty standard.
The lack of context may be for the purpose of generalization--it is not a single game, but can be used for a variety of connection games and jumping games.

I recently purchased five of these from excess inventory (surplus) sales from a correctional institute.  These were used in inmate mental status.  I paid $1.00 each for them.


text:
Can you win at level 8 in Munchkin?
A friend played Munchkin Deluxe the other day and told me he won at level 8 when he killed a monster which granted 2 levels. To my understanding, I thought you NEED to kill at level 9 in order to win.
Can anyone explain if this is correct or not?

What made you believe that you need to be level 9?

Indeed, there's no such rule.

You can even win at level 7 (there are cards that add 1 level to the rewards of a defeated monster).

theoretically you can even win at level 1, although it's highly unlikely to happen

Welcome to Board & Card Games. Please check the mark next to the answer to accept it. If not, please identify your problem with it.

From the Munchkin Rules:

The first player to reach Level 10 wins . . . but you must reach Level 10 by
  killing a monster, unless a card specifically allows you to win another way.

The only requirement it gives is that you kill a monster to reach Level 10, it doesn't say you have to be Level 9 when you kill it. The only other rules about winning say you can't reach Level 10 by selling loot or playing a Level Up card.
From the Munchkin FAQ:

Note also that ANY level gained as a result of killing a monster counts as the winning level. If you have a Race or Class ability that lets you get an extra level after winning certain combats, that level can be the winning level.

This supports the idea that you don't have to be Level 9 when you kill a monster, you just have to get to Level 10 as a result of killing a monster.


text:
What happens if you are unable to draw because your library is empty?
In Magic the Gathering, what happens to a player if they get their draw phase, but are unable to draw a card because their library is empty?

They lose the game.

120.4. A player who attempts to draw a card from a library with no cards in it loses the game the next time a player would receive priority.
104.3c If a player is required to draw more cards than are left in his or her library, he or she draws the remaining cards, and then loses the game the next time a player would receive priority.
704.5b If a player attempted to draw a card from a library with no cards in it since the last time state-based actions were checked, he or she loses the game.

Can you provide any context for why this rule is repeated so many times? If you feel like it, you could also describe the flavor behind these rules. According to this article by Mark Rosewater, losing by drawing on an empty library is essentially a death by going mentally insane. And finally, I can't find anything about this in the basic rules. I find that surprising, given that it is repeated three times in the comp rules.

@Rainbolt It is repeated in the sections on Drawing Cards, Losing the Game, and State Based Actions

The CompRules are known to repeat a lot of rules in several places, nothing unusual about this rule in particular in that sense.

The previous version of the basic rules had this: "You also win if your opponent has to draw a card when none are left in his or her deck, or if a spell or ability says that you win." I think they tried to do a lot of simplification in the most recent version, and unfortunately cut that out. There are a lot of other good things about the previous edition too. (It's ~twice as long, so I guess it's less basic, but it has a lot of really helpful information, and it's still all understandable.)

And the three repetitions are covering different details. First one is part of drawing cards (namely, what happens if you can't). Second one enumerates it as part of the list of ways to lose the game. Third one enumerates it as part of state-based actions (in the timing sense). In a sense, it's "When you're drawing cards..." vs "You lose the game if..." vs "While checking state-based actions..." Same result, but different perspectives.

@Cascabel Yes but there's a difference between the basic rules and the comprehensive rules either way.

@Andrew Of course. The point wasn't that they're the same, just that (at least in the past) there was a very simple rules reference that covered this. It can be nice to try to provide newer players with explanations and resources that are a little more understandable than the full comprehensive rules.

When a player is forced to draw a card and can't they lose the game. This is covered in the comprehensive rules in a few places, due to the rule fitting into multiple places:
Ending the game:

104.3c If a player is required to draw more cards than are left in his or her library, he or she draws the remaining cards, and then loses the game the next time a player would receive priority. (This is a state-based action. See rule 704.)

Drawing a card:

120.4 A player who attempts to draw a card from a library with no cards in it loses the game the next time a player would receive priority. (This is a state-based action. See rule 704.)

State based Actions:

704.5b If a player attempted to draw a card from a library with no cards in it since the last time state-based actions were checked, he or she loses the game.

There are cards that modify this, most notably Laboratory Maniac and Jace, Wielder of Mysteries which change drawing from an empty library from a loss to a win. There are also cards which would stop the draw from happening, like Omen Machine or Maralen of the Mornsong, preventing the state based action. A card like Platinum Angel, which prevents game loss would simply negate the loss and let the game continue.


text:
If a spell is countered, do on cast effects still get triggered?
If I cast a spell that has an "on cast" effect, does the effect still trigger even if the spell is countered? For example, if I play Ulamog, the Ceaseless Hunger and it gets countered by a counter spell, do I still get to exile 2 target permanents?

This does not look like a duplicate of that question at all. That one is asking about if an opponent can tap his lands that are targeted for exile by Ulamog; this one is about if you still get the exile effect if Ulamog is countered.

Yes. A player doesn't have a chance to cast a counterspell until after you have finished "casting" your spell, and any "when cast" triggers are triggered and put on the stack. At that point, a player could counter your spell, but the triggered ability is still there as a completely separate thing.

601.2. To cast a spell is to take it from where it is (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect.
112.7a Once activated or triggered, an ability exists on the stack independently of its source. Destruction or removal of the source after that time won’t affect the ability.

Sidenote if anyone comes here looking for answers about Throne of Eldraine's new Adamant mechanic. WoTC have stated that the Adamant check only goes on the stack when the spell resolves, even though the help text is worded like a casting trigger

A small point of clarification: If your opponent counters your Ulamog, the Ceaseless Hunger with Summary Dismissal it will counter both the spell and the "when you cast" triggered ability. Similarly, your opponent could use a couple spells to counter your spell (e.g., with a Ceremonious Rejection) and the triggered ability (e.g., with a Stifle or Disallow).

This isn't entirely accurate: (1) Summary Dismissal doesn't counter, it exiles; and (2) Summary Dismissal exiling Ulamog isn't what counters/exiles the "when you cast" triggered ability, Summary Dismissal exiling the triggered ability specifically is what exiles the ability (in addition to Ulamog, which is a wholly unrelated event for this purpose).

@doppelgreener is 1 for 2. Summary Dismissal doesn't counter Ulamog, but exiles it from the stack, but it does counter the triggered ability with the condition "When you cast..."

@DrunkCynic afaik, immediately after casting ulamog, the triggered ability goes on the stack — before anyone receives priority and can cast Summary Dismissal. If Ulamog was countered, the triggered ability would then resolve independently anyway (as a ruling on Ulamog notes).

@doppelgreener He was just pointing out that Summary Dismissal doesn't exile abilities, it counters them. So your first point is only half right (it does exile the spell, just not the ability). So you're more like 3 for 4.

Oops. You're right! I thought it read exile all spells and abilities! Thanks for that correction.


text:
Can I have two similarly-named legendary creatures on the field?
If I have two different Ulamogs, can they both be on the field? They both share Ulamog as part of their name, but their entire names are different.

One is Ulamog, the Ceaseless Hunger, while the other is Ulamog, the Infinite Gyre. Does legend rule carry across instances like this, or would it only apply if I had two of either of them on the field?

Legendary permanents trigger the Legend Rule only if they have the same exact name.
Ulamog, the Ceaseless Hunger and Ulamog, the Infinite Gyre have two different card names, so you can have both out simultaneously (even though they're both variants of Ulamog, lore-wise).

201.2. A card’s name is always considered to be the English version of its name, regardless of printed language.
201.2a Two objects have the same name if their names are identical.
704.5j If a player controls two or more legendary permanents with the same name, that player chooses one of them, and the rest are put into their owners’ graveyards. This is called the “legend rule.”

Planeswalker cards used to have a slightly different uniqueness rule:

306.4. Previously, planeswalkers were subject to a “planeswalker uniqueness rule” that stopped a player from controlling two planeswalkers of the same planeswalker type. This rule has been removed and planeswalker cards printed before this change have received errata in the Oracle card reference to have the legendary supertype. Like other legendary permanents, they are subject to the “legend rule” (see rule 704.5j).

This used to be the case if you, for example, controlled Ajani Goldmane and Ajani Steadfast. One of them would die, not because they have similar names, but because they both have the same planeswalker type, Ajani.
The planeswalker uniqueness rule has been removed with the Ixalan rules update. All planeswalkers have received errata to be legendary, they follow the regular legendary rule now, and their planeswalker type does no longer matter for uniqueness.


text:
How do cards with multiple Xs in their mana cost work with cards that reduce their costs?
For example, if I have Astral Cornucopia in play along with Jhoira's Familiar, what happens? Can I cast it for X = 1 without paying any mana?
I know that there is a question here regarding to X spells with cost reducers, but the question does not cover spells with multiple Xs, which is why I am asking this.

Casting Astral Cornucopia with X=1 and Jhoira's Familiar in play will cost {2}.
The number of Xs in a casting cost doesn't matter for cost reduction effects. If you choose X=1, the mana cost of Astral Cornucopia will simply be {1}{1}{1}, or {3}, the sum of mana symbols. Jhoira's Familiar will reduce the mana cost by {1}, resulting in a total cost of {2}.

202.1a The mana cost of an object represents what a player must spend from their mana pool to cast that card. Unless an object’s mana cost includes Phyrexian mana symbols (see rule 107.4f), paying that mana cost requires matching the type of any colored or colorless mana symbols as well as paying the generic mana indicated in the cost.
601.2f The player determines the total cost of the spell. Usually this is just the mana cost. [..] The total cost is the mana cost or alternative cost (as determined in rule 601.2b), plus all additional costs and cost increases, and minus all cost reductions.[..]

Alright, that makes sense. I wanted to check, as I could see it going either way, and I am not well versed enough in the rule books to go searching for information.

No, if X = 1, then the card costs 2 to cast.
When casting a card with X in the cost, you choose a value for X. Then, you calculate the cost of the card based on your chosen X.

601.2b [...]If the spell has a variable cost that will be paid as it’s being cast (such as an {X} in its mana cost; see rule 107.3), the player announces the value of that variable.
601.2f The player determines the total cost of the spell. Usually this is just the mana cost. Some spells have additional or alternative costs. Some effects may increase or reduce the cost to pay, or may provide other alternative costs.

All Jhoira's Familiar does here is to reduce the total cost (normally 3) by 1.


text:
How do dash costs work with commander tax?
If I have the card Zurgo Bellstriker as my commander, and I cast it for its Dash cost, do I have to add commander tax to it? Or does the Dash cost override it?
My gut tells me I would still have to pay commander tax, but I am checking regardless.

Yes, the additional casting cost still applies.
The dash cost of Zurgo is an alternative cost, while the "commander tax" is an additional cost. You simply add them together for the total cost of casting your commander.

903.8. A player may cast a commander they own from the command zone. A commander cast from the command zone costs an additional {2} for each previous time the player casting it has cast it from the command zone that game.
702.108a Dash represents three abilities: two static abilities that function while the card with dash is on the stack, one of which may create a delayed triggered ability, and a static ability that functions while the object with dash is on the battlefield. “Dash [cost]” means “You may cast this card by paying [cost] rather than its mana cost,” “If this spell’s dash cost was paid, return the permanent this spell becomes to its owner’s hand at the beginning of the next end step,” and “As long as this permanent’s dash cost was paid, it has haste.” Paying a card’s dash cost follows the rules for paying alternative costs in rules 601.2b and 601.2f–h.
601.2f The player determines the total cost of the spell. Usually this is just the mana cost. Some spells have additional or alternative costs. Some effects may increase or reduce the cost to pay, or may provide other alternative costs. Costs may include paying mana, tapping permanents, sacrificing permanents, discarding cards, and so on. The total cost is the mana cost or alternative cost (as determined in rule 601.2b), plus all additional costs and cost increases, and minus all cost reductions.[..]


text:
Finding the CIN of MTG Cards for collection on recent (2017-ish) MTG cards
I collect MTG cards and after hoarding a huge collection I'm trying to get it all organized now from this mess.
I've found an xls file that has almost all of the cards on it but it's not updated for the latest 2-3 sets.  I can find an input all the information required for those but I don't know where to find the info for this "CIN" column - it looks like it is just the abbreviation of the set name and then the card number within the set?  How do I know what the abbreviation is and is there anywhere I can just look up this information?

Just from context clues, CIN is probably Card Identification Number, and that doesn't seem to be a standard thing for Magic cards.

I agree - I have never searched for anything with CIN or talked about it but from the files I've seen and collections a lot of them do include this column labeled CIN so it made me curious as to what it was.  I also wanted the additions to my file to be complete when I add cards to it in the future

You have the CIN for some cards, right? Provide a bunch of examples. The more the merrier. In fact, if you uploaded your spreadsheet to Google docs, made it public, and linked to that so we could have thousands of examples, that would be awesome. Maybe someone with a keen eye will spot a pattern.

"CIN" probably stands for "Card Identification Number" or something similar, just based on context. This does not appear to be a commonly used term online when discussing Magic: the Gathering.
The abbreviation for each set is officially decided by Wizards. You can find these abbreviations at http://en.wikipedia.org/wiki/List_of_Magic:_The_Gathering_sets or http://mtg.wikia.com/wiki/Set.

I think that is what I needed thank you.  Yes I think it stand for Card Identification Number , some examples include RB22 for a card that is the 22nd Black mana card from Revised Set.   I can figure out the number and color letter just didn't know where to find abbreviation for the code from the set.
There are a few descrepancies like Scourge is set as SCG but in the codes in my current xls file they just use SC and then letter for the color and # following so maybe it is just the first two letters of the abbreviation.

Note that Wikipedia lists the Revised Edition code as "3ED", while it looks like your spreadsheet is just using "R".

Assuming CIN is the collectors number, that number is printed on the card:

In this example, the first card of Ixalan, we see the set abbreviation as XLN and the number as 001.
Older cards (pre M15) are laid out differently:

In this example, the first card of Journey into Nyx, we see the number within the set 1/165, but prior to M15 the set abbreviation was not printed on the card. To find set abbreviations for these sets, the most complete list I have found is on Wikipedia here.
Cards are numbered in a set by color then alphabetically within the color, going in order clockwise around the color wheel White, Blue, Black, Red, Green then Multicolor, Colorless (including nonbasic land) and last Basic Land. Planeswalker decks have added cards past the set size, these do not follow the same ordering rules for numbers.


text:
Essence Scatter and summoning creatures
I played Nessian Game Warden, and a friend of mine tried to counter the entire summoning using Essence Scatter.
Essence scatter says:

Counter target creature spell.

Does Nessian Game Warden go to the graveyard since its summoning hasn't yet resolved or does essence scatter's effect only apply to the ability on the card and NGW is summoned?

The Nessian Game Warden is countered. It does not resolve, and its ability does not go on the stack or resolve. It goes immediately to the graveyard.
"Creature spell" in Essence Scatter's text refers to the creature card itself, and not the ability on it.
Basically, if you cast Nessian Game Warden and it isn't countered, gameplay proceeds like this:

You cast Nessian Game Warden. The Nessian Game Warden card goes on the stack, and players have a chance to resolve.
Nobody responds and Nessian Game Warden resolves. Nessian Game Warden enters the battlefield.
Nessian Game Warden's triggered ability triggers and goes on the stack.
Nessian Game Warden's triggered ability resolves, and you do what it says.

In the situation you describe, here's what happens instead:

You cast Nessian Game Warden. The Nessian Game Warden card goes on the stack, and players have a chance to resolve.
Your opponent responds by casting Essence Scatter, and that goes on the stack on top of Nessian Game Warden.
The Essence Scatter resolves, countering Nessian Game Warden. Nessian Game Warden goes to the graveyard.

So even if the creature doesn't have any abilities essence scatter would essentially kill it before it goes onto the battlefield?

As I said, the creature spell is the creature, not the creature's abilities. When you cast a creature, like any spell, it goes on the stack. When it's there, it's not on the battlefield, so its abilities (usually) don't matter.


text:
Are tribal spells with changeling considered creature spells?
Does Heartless Summoning make Tribal Changeling Instants cheaper to cast? Crib Swap's type line says:

Tribal Instant - Shapeshifter

In the reminder text it says:

Changeling (This card is every creature type at all times.)

So is Crib swap a creature or not, and if not, does Heartless Summoning affect it in any way because of the Changeling clause?

The spell is not a creature spell, so it is not affected by Heartless Summoning. The Changeling ability says that the card has "all creature types", but "creature type" is just the name for the subtypes that Creature and Tribal share. So, Changeling doesn't make the card a creature, it just makes the card have all of the creature subtypes.
The relevant rule is 205.3m :

Creatures and tribals share their lists of subtypes; these subtypes are called creature types.

What part of rule 205.3m is relevant? "Creatures and tribals share a subtype; therefore, tribals are not a creature spell." I don't follow.

Changling says that the card is "every creature type at all times." The rule says that subtypes of the tribal type are called "creature types". The point is that saying that a card has "every creature type" does not imply that it has the Creature type.

Creature and tribal type spells have a species subtype known as "creature type".

Heartless Summoning has the following ability:

Creature spells you cast cost 2 less to cast.

Creature spell means a spell on the stack with the type Creature.
However Crib Swap has types Tribal and Instant, neither of which is Creature.
Thus Crib Swap is not affected by Heartless Summoning.
Lets contrast this with a card that cares about sub-types (of which both Tribal and Creature share creature types). Ballyrush Banneret would cause Crib Swap to cost 1 less as it is a Kithkin spell, a spell with the sub-type Kithkin.

No.
"Goblin", "Elf" and "Druid" are creature types (aka creature subtypes). Changeling grants all creature types.
Crib Swap is a Shapeshifter (a creature type).
Crib Swap is a Goblin (a creature type).
Crib Swap is a Druid (a creature type).
"Creature" is a card type, not a creature type. Changeling doesn't grant any card types.
Crib Swap is a Tribal (a card type).
Crib Swap is an Instant (a card type).
But Crib Swap is not a Creature (a card type)
Crib Swap can have creature types without being a creature because creatures and tribals share their lists of subtypes[CR 205.3m].

Changeling isn't a creature type, is it? It's a keyword that grants all creature types.

@GendoIkari, Oops, I meant Shapeshifter. Fixed.


text:
Can crackleburr respond to himself?
Let's say my opponent has a Crackleburr, two red and blue useless tokens, and an infinite amount of red and blue mana. Crackleburr's card text is this:

{U/R}{U/R}{T}, Tap two untapped red creatures you control: Crackleburr deals >3 damage to target creature or player.

{U/R}{U/R}{Q}, Untap two tapped blue creatures you control: Return target creature to its owner's hand.

Now let's say that my opponent, on his turn, activates Crackleburr's first ability to kill a creature of mine. I respond with Path to Exile on Crackleburr. Can Crackleburr respond to that Path to Exile by activating his second ability? Then, assuming it can, can Crackleburr respond to his second activation by activating his first ability again? So, with infinite mana, can Crackleburr continually respond to itself?

As long as you can pay the cost, you can activate the ability.

@ikegami As long as you can pay the cost and you have priority you can activate the ability.

@Rainbolt, He has priority.

@ikegami He can pay the cost.

A player could, in fact, repeatedly activate Crackeburr if the player had the mana to do so, as long as the player had two other creatures available that were both red and blue, because the tapping and untapping are costs and not effects.
Each time the player would have to pick targets for the effects - and could keep picking the same targets over and over again if desired. The effects with targets would go on the stack, so that you would have a stack consisting of the three-damage effect at the bottom, then the return-to-hand, then three-damage, then return-to-hand, etc. Instances of either effect would fizzle if they targeted creatures that were already returned to hand or destroyed via damage. (Bear in mind that damage doesn't use the stack, so as soon as a Crackleburr invocation is resolved because the stack unwound to that point, then if the creature has lethal damage, it will be destroyed.)
Presumably your opponent used Crackleburr's untap ability specifically to bounce itself. This would work, and yes, your opponent could tap it a third time to do three damage if there were mana and untapped creatures available. At that point these things happen in order as the stack unwinds:

Crackleburr does three damage to the second target
Crackleburr returns itself to its owner's hand
Path to Exile tries to exile Crackleburr but fails because the target is no longer on the battlefield
Crackleburr does three damage to the first target

Wow. Nice. Clarification, why does step 4 still happen if Crackleburr is no longer on the battlefield?

@sillyputty see http://boardgames.stackexchange.com/questions/7893/does-an-activated-ability-resolve-if-the-card-with-the-ability-leaves-the-battle

Outside of casual magic, you have to explicitly hold priority in order to build stacks like the one described in this answer.


text:
How do Aether Rift and Library of Leng interact?
Let me give you a run down of the board state.
I had an Elderscale Wurm enchanted with Canopy Cover on the battlefield. Damage could not reduce my life total below 7.
My opponent had Forgestoker Dragon on the battlefield and a lot of other, smaller creatures. He could pay to kill any other creature that came out on the battlefield, but had no effects in his deck to deal with Elderscale Wurm nor Canopy Cover.
Similarly I had no way to deal with his dragon, and if I attacked with my Elderscale Wurm it would die, and I would lose to his horde.
But, I had one more card in my library than he did, so we assumed I would eventually win until we looked at the other two cards my opponent had on the battlefield- Aether Rift and Library of Leng.
Aether Rift says:

Enchantment
At the beginning of your upkeep, discard a card at random. If you discard a creature card this way, return it from your graveyard to the battlefield unless any player pays 5 life.

Library of Leng says:

Artifact
You have no maximum hand size. If an effect causes you to discard a card, discard it, but you may put it on top of your library instead of into your graveyard.

My opponent only had creatures in his hand. He wanted to use the interaction between these two cards to randomly discard a card, not pay 5 life,(I could not pay the 5 life cost because it would bring me below 7 life, negating Elderscale Wurm's effect) and have it go back to the top of his library, so that he would have 1 more card than I did, thus I would mill out before he did.
Is that how this interaction works?

Even though you both think this is how it would turn out I would still play it out. You can always have forgotten about a card that can deal with the situation. Being it a buff for your dragon so you can attack, or a way to deal with the enchantment or artifact or something else to kill him. It doesn't need to take much time. You could agree about a shortcut with him skipping all his turns and you keep drawing cards (and discarding if you have more than 7) until your deck is empty

At a tournament you'll seriously want to consider conceding in order to have any hope of winning the match before time runs out.

He would be able to put a card on top of his library in order to not lose, but not quite the way you are thinking it works.
What happens is a the beginning of your opponent's upkeep Aether Rift's ability goes on the stack, and when it resolves they discard a card at random. when the card gets discarded Library of Leng's replacement effect occurs allowing your opponent to put the card on top of their library. If they chose to put the card on top of their library the rest of Aether Rift's ability doesn't apply since as far as the game knows a creature card was never discarded (a card was discarded if anything else cares about that, but nothing is known about that card, including its type [CR 701.7c]). Your opponent will then draw the card they just "discarded" at the beginning of their draw step. They can keep repeating this process until you run out of cards in your library.

"Aether Rift's ability doesn't apply since a creature card was never discarded." This isn't correct. It specifically says that the card is still discarded. Which means that players will still have an opportunity to pay 5 life. But if they don't pay the life, then the card will fail to return to the battlefield because it is not in the graveyard.

@Gendolkari This is what I get for assuming what a card does and not reading the rulings :)

Wait, never mind I was right. The card is still discarded, true, but since the effect discarding the card doesn't tell you to reveal the card the card remains unrevealed and no characteristics of the card are known, and the paying life is dependent on it being a creature that was discarded. CR 701.7c

Ah, interesting. Makes sense; I wouldn't have thought of that though!

@diego So when my opponent has these two cards out, he randomly discards a card, doesn't reveal what it is, and decides (without knowing what he is discarding) to put it in the graveyard or on top of his library?

@sillyputty He would get to look at it before deciding where it goes. From the Gatherer rulings: "You can look at a randomly discarded card before deciding where it goes."

It seems to me like Gendolkari has a point (first comment) and diego has a point (third comment) and these two points conflict with one another. Are we all agreeing that because the card wasn't revealed, it can't possibly trigger anything? Is there a rule to back this up?

@Rainbolt From the Library's rulings: "Since the card goes directly to the library, the card is not revealed unless the spell or ability requiring the discard specifically says it is." Since the effect doesn't require the card to be revealed it isn't, and because of 701.7c we don't know anything about the card, including types. Because of this the 2nd part of the Rift's ability never happens because a creature was never discarded.

@diego A creature was discarded. The only difference is that it was hidden information. There are a few others in this thread that would agree. I will ask this as a separate question though to avoid working it out in the comments here.

@Rainbolt A card was discarded, the game doesn't know anything about it though, because of 701.7c its type is undefined. Yes, the person that put it there knows what it is, but their opponent doesn't, and the game can't get that information. Waste Not works in that thread because it has a condition for non-creature non-land, which not having defined characteristics the discarded card is.

@diego Well, no. A creature card was discarded. If you decide to add this to your answer, I would suggest improving the wording to say "The game doesn't know a creature card was discarded." instead of saying "A creature card was not discarded." when the latter is obviously false.

@Rainbolt Yes, that is exactly what I meant. I thought I made that clear several times, but I will try to do a better job in the future.

@Rainbolt I made a slight edit, does that make more sense to you?

@diego The only thing I would change is "[...] nothing is known about that card, including its type, due to CR 701.7c [...]". The interaction is complex enough to warrant the reference to CR (IMO). Other than that, looks good.

So with all of that out of the way, can my opponent abuse this by randomly discarding a card, waiting til I see if I'm going to pay the 5 life, and then decide whether to put it into the graveyard or on top of his library?

Also, the act of "discarding" doesn't mean putting it into the graveyard, then, I take it? So it's not like he's "discarding" the card into the graveyard, then deciding he'd rather have it on top of his library? That's how I thought it worked, which is why I was confused as to where the card would go. One card says "battlefield", the other says "library". But thank you for the answer. Very helpful!

@sillyputty No, if they want to put it on top of their library they have to do it before you would choose to pay life

@sillyputty Library of Leng is a weird card, it still counts as discarding the card even though the card move straight from their hand to their library without getting revealed and without hitting the graveyard

Yes, it would work that way. The paying 5 life is actually irrelevant here, because if he chooses to put the card on top of his library, then the creature will fail to return "from the graveyard to the battlefield", because it won't be in the graveyard. His library shouldn't ever shrink in fact; each turn he will discard a card, putting it on his library, then draw that same card.

Rather than "library shouldn't ever shrink", I would say it oscillates between having n and n-1 cards. Depending on which measurements of the library size you're comparing, you'll get equal or different numbers. If you compare library sizes before and after drawing a card in the draw step they're different (likewise before/after the discard effect). If you look at the same point in the phase/step sequence across different turns, they're equal.


text:
When a permanent is being made to copy another, does it count as entering the battlefield?
I want to cast Polymorphous Rush on a strong creature on my battlefield so that my Hamletback Goliath's ability will trigger.  The creature that will become the copy is already on the battlefield, but when it becomes a copy of the strong creature, will this trigger my Hamletback Goliath's ability?
For reference, Hamletback Goliath reads:

Whenever another creature enters the battlefield, you may put X +1/+1 counters on Hamletback Goliath, where X is that creature's power.

No, it will not trigger the Goliath since nothing is entering the battlefield, a creature is just changing characteristics.
What you can do, however, is wait for a new creature to enter the battlefield and trigger the Goliath. With the trigger on the stack, you can then Polymorphous Rush the triggering creature, and the Goliath will get counters based on the new power. This is because the Goliath's ability doesn't check to see what the power of the creature is when it enters, it checks as the ability is resolving.

The answer is stated plainly by comprehensive rule 706.4.

706.4. Some effects cause a permanent that’s copying a permanent to copy a different object while remaining on the battlefield. The change doesn’t trigger enters-the-battlefield or leaves-the battlefield abilities.

However, as you might have guessed by reading the other answers, this rule is redundant. Rule 603.6a tells us what we need to know.

603.6a Enters-the-battlefield abilities trigger when a permanent enters the battlefield. [...]

Rule 603.6a doesn't care what the permanent's name is. It just cares that it is a permanent. The permanent could change names a hundred times, and it would still be the same permanent, (sitting there on the battlefield).

I think the rule is needed. Or at least, you need the rule explaining when "enters the battlefield" triggers trigger. Because the confusion comes from the fact that even though "the object" was on the battlefield before, "Hamletback Goliath" was not. So without rules saying otherwise, it's just as logical to say "Hamletback Goliath was not on the battlefield before, but now it is."

@Gendolkari It would be odd if the rule were necessary when there are three other answers without it, one of which has 5 upvotes.

@Gendolkari Also, we don't care if the name "Hamletback Goliath" is or is not on the battlefield. In fact, it doesn't even make sense to talk about a creature's name being somewhere. We care about the object, not the name. Should I add this comment to the answer, or do you have a better way to word this?

That is a fair point; I'm just trying to put myself in the place of someone who doesn't understand all the details of the rules. I actually think that 603.6a the rule that makes 706.4 redundant... 603.6a is needed to explain that what matters is the permanent entering the battlefield; NOT "Hamletback Goliath" entering the battlefield.

@Gendolkari I like the look of this much better. The bulleted list that I had before sounded condescending for some reason that I can't really put my finger on (maybe the bold font).

Upvoted because redundant or not; answers with rules quotes are better.

No. The creatures are already on the battlefield and merely change by copying the original, so they don't enter the battlefield.

No. Using Giant Growth or Polymorphous Rush to modify the characteristic of a permanent does not cause it to change zones. No creatures left or entered the battlefield.


text:
Can I declare Brood Sliver's tokens as attackers?
So in my Sliver deck I am running Brood Sliver and Heart Sliver. Let's say they're both on the battlefield, and a sliver deals damage to a player. Could I declare the tokens made as attackers or is it too late?
Sorry if this question probably has an obvious answer, it's just something I was wondering about.

If you somehow managed to create an additional combat phase, they would be able to attack in that one.

You might want to check out Aggravated Assault. I have a Sliver Commander deck, and I find it quite fun. Especially with Manaweft Sliver and 5 other Slivers.

No, you can't attack with those Sliver tokens the same turn you get them. In your combat phase, the following steps happen:

You declare what creatures are attacking.
Your opponents declare what creatures are blocking.
Combat damage is dealt.

Brood Sliver's ability triggers when a Sliver deals combat damage, so it is only in the Combat Damage Step that you get the tokens. At this point you have already finished dealing damage, so there's no chance to attack with the new tokens.


text:
Brutal Hordechief & Bloodthrone Vampire
I have a timing question: Is it possible to attack with "Bloodthrone Vampire" and let's say 10 other creatures at the same time, while using BOTH abilities of "Brutal Hordechief" and therefore cause 30 damage with only 1 creature actually causing damage?
In Detail:

My opponent has 15 creatures on the battlefield.
I attack with Bloodthrone Vampire and 10 other creatures. Since Brutal Hordechief is on the field, I cause 11 damage to my opponent due to Hordechief's first ability.
Then I want to sacrifice 9 of my 10 other attacking creatures in order to give Bloodthrone Vampire +18/+18, causing another 19 damage to my opponent.
Since I have used Hordechief's 2nd ability (spent 5 mana), all my opponent's creatures should have blocked the last of my 10 attacking creatures (the one I didn't sacrifice with my Vampire's ability).

Therefore I caused 30 damage using Bloodthrone Vampire and Brutal Hordechief's first ability, right?
Or is there a timing error somewhere along the way?

"Since Brutal Hordechief is on the field, I cause 11 damage to my opponent due to Hordechief's first ability." - Correction; your opponent loses 11 life. This is important: it's not damage, so they can't prevent it using effects like Channel Harm.

Assuming you have Bloodthrone Vampire and 10 other creatures:

You have successfully activated Brutal Hordechief's ability.
During the declare attackers step you declare 11 attackers. Brutal Hordechief's ability triggers, you gain 11 life and the opponent loses 11 life.
During the declare blockers step, you can choose how enemy creatures block since you activated Brutal Hordechief's second ability. You can choose all 15 creatures to block one of your 10 creatures.
After this, you get priority and you can sacrifice 10 of your creatures to give your Bloodthrone Vampire +20/20. Assuming the opponent doesn't have anything to respond, Bloodthrone Vampire will deal 21 damage (for a total of 32 damage).

Some extra strategy tips:
Also note that you can deal even more damage if you choose not to sacrifice creatures with power more than 2 (and even 1 unless you fear your opponent can get rid of a group of small creatures).
For example, say 2 out of 10 creatures are 1/1, 4 are 2/2 and 4 are 3/3. You can choose enemy creatures to block one of your 1/1 creatures, sacrifice them, and you will deal 5 damage with your vampire, 8 damage with your 2/2 creatures and 12 with your 3/3 creatures, with a total of 25 damage. Add 11 life loss to that - opponent loses 35 life this combat phase, and you still have 9 creatures alive if the game goes on.

Super! Great Answer!

@Vilmar If that stuff is worth saying it should probably be in your answer; comments are transient and can/will get deleted eventually.

@Klausi If this answer satisfies your question, you can on click the green check mark next to the answer to accept it. This rewards the author, and it lets others know that your question was answered. You can always come back and change it later if a better answer comes along.

Therefore I caused 30 damage using Bloodthrone Vampire and Brutal Hordechief's first ability, right??

Yes

Or is there a timing error somewhere along the way?

Yes
You will deal 30 damage, but your steps are a little bit incorrect. How it should be:

Combat phase begins(rule 507)
You choose an opponent who becomes a defending player(but since you're only playing with 2, you can only choose the other player, so basically you do not have any choice here)
Declare attackers step starts(rule 508)
You choose all your creatures to attack
Then triggered abilities go on the stack(Brutal Hordechief's first ability)
When this ability resolves, you get 11 life and your opponent loses 11 life. (This isn't damage, it's life loss, which is important because effects like that of Channel Harm won't be able to do anything about it.)
Declare blockers step starts(rule 509)
Second ability of Brutal Hordechief will let you choose the blockers. You may let them all block one of your tiny creatures
Then you get the priority(rule 509.5)
Now you can activate Bloodthrone Vampire's ability and sacrifice 9 creatures to give your Bloodthrone Vampire +18/+18. Because 9 of your creatures were removed from combat after declare blockers step, your opponent can't choose new targets to block
Combat damage step starts(rule 510)
Combat damage is dealt simultaneously, so your unblocked 19/19 Bloodthrone Vampire deals damage to your opponent and his creatures do nothing(because they were blocking a creature that were removed from the battlefield)

So this sums up to 30 damage + damage of that 1 creature that you didn't sacrifice(which is probably Brutal Hordechief), so in total you would deal 33 damage

I've added a note about it being life loss when the asker called it damage; please review my addition and edit it further if you like.

Two things, in the interest of not confusing new players: you left out any mention of activating Brutal Hordechief's second ability, which of course has to be done before the declare blockers step; and in step 6, technically it's 11 individual triggered abilities that each make the opponent lose 1 life and the player gain one life.


text:
Aura Trample removed by High Priest of Penance
I've been searching high and low for this: say a High Priest of Penance (with an indestructible aura) blocks a creature with Rancor, i.e. trample. Can I stop the trample effect by destroying either the creature or the enchantment, before trample happens? Since it first assigns damage to the priest who then can destroy a permanent...?

702.19b The controller of an attacking creature with trample first assigns damage to the creature(s) blocking it.

You can't stop your opponent from trampling over your High Priest this way. Although you are correct that trample damage is not assigned simultaneously between creatures and players, it is dealt simultaneously.

510.2 Second, all combat damage that's been assigned is dealt simultaneously.

So both you and your High Priest are dealt damage at the same time. At that point, you may use your Priest's ability, but destroying the attacking creature or aura will have no effect on what already happened.