text:
Is there a reason effects that introduce another combat phase also create another main phase?
In Magic, there are a number of effects that create an additional combat phase. In any example I've seen, they either also create an additional main phase, or else they can only be cast/activated during combat (meaning the additional combat phase will happen, followed by the next main phase). Is there a reason for this? (Besides the reason of: the game designers designed it that way)
A different way of phrasing my question could be: would something hinder the game from continuing if an effect caused combat to not be followed by a main phase? (For example, Precombat Main Phase -> Combat -> Postcombat Main Phase -> Additional Combat -> End Step)
If not, has any justification been given for the apparent design rule that a main phase should always happen before the End Step?

I guess they don't want that the structure of a turn changes. Don't know the real reasons, though.

There's lots of reasons to cast stuff after combat. Being denied that opportunity would be a significant disadvantage.

Agreed. Given that, it seems like that could be a useful tool in lowering the power of a card that gives additional combat. It just seems odd that it's a tool WotC has never used. I wasn't sure if there was some rules-dependent reason.

No, there is nothing preventing this from a rules perspective.  Maintaining the flow of the turn (as murgatroid99 mentioned) is probably why this template has been preserved over time, but the origin of this template comes from the fact that the early rules of the game did not support such a turn structure.
Up through 5th Edition, combat did not have its own phase.  "Attacking" was an optional action that you could enter during your Main Phase.  Entering combat was essentially a special action a player could choose to take like playing a land.  As such, combat was wholly contained within a singular Main Phase, and combat was not standalone.  The very first card to do this kind of effect was Relentless Assault from Visions.  The relevant part of the original text was this:

You may declare an additional attack during your main phase this turn.

So this automatically functioned the way it does today since every combat happened within a Main Phase and would kick you back out to the Main Phase when they were complete.  When combat was promoted to its own phase in the Sixth Edition rules update and split up the Main Phase to pre- and postcombat, the card received a new printing with wording that would allow it to function the same under the new rules:

You get an additional combat phase followed by an additional main phase this turn.

After that, this kind of wording became the standard for effects that create additional combats in the turn.  Wizards tends to normalize templates for effects that are used on multiple cards so that players don't have to remember the slight differences between the different implementations, and this has been the basis for templating this particular effect from that point onward.

The rules do not require the cards to be written that way, or in general for the final combat phase to be followed by a main phase. The card Fatespinner, for example, can cause players to skip main phases, and go directly from the draw step to combat to the end step.
That implies that there are other reasons that these cards are consistently written this way. The simplest explanation is that having a final main phase to allow the active player to cast post combat spells is an important aspect of the turn structure that Wizards wants to preserve when granting players additional combat phases.


text:
Is morphing a creature effectively a cost?
I'm teaching some of my friends magic, and morph seems to be a bit of an outlier mechanic. It's one of the few things that a player has a choice to do but 'doesn't use the stack'. It can make it a bit hard to describe to my new players that are just learning how the stack/abilities resolving work.
Is it fair to describe morph as a cost (paid in addition to the actual morph cost), which does nothing? Effectively, rewording it as

[Cost], turn this creature face up: Do nothing.

Of course, once a creature is turned face up there are effects, such as a change in the creature's power and toughness, and (usually) triggered abilities, but those are only a consequence of an action happening, not a new action paid for by the morph cost.
In my understanding, treating morph as a cost in this way is entirely keeping with the rules. As normal costs, it can only be done when you have priority. Similarly, it can't be responded to. (A creature sacrificed as a cost, as an analogy, cannot be responded to either.)
My question is: is this a fair way of explaining the special case of Morph as a mechanic to newer players, or is there some rule or corner case that I'm missing?

I suggest checking rules section 116 for a list of most of the actions that do not use the stack.

Turning a creature face up by paying its Morph cost is a Special Action, like playing a land.
Taking a special action is similar to paying a cost to cast a spell or activate an ability, in that both take effect immediately without waiting for anything on the stack to resolve, but there are also differences. Players can explicitly take special actions whenever they have priority, but costs can only be paid as part of taking some other action. So, any attempt to represent it as a cost would make it part of another action that does nothing except provide an opportunity to pay that cost, which is essentially backwards.
If Morph was represented as a cost to activate a nothing ability as described in the question, that action could not be taken while you cannot activate non-mana abilites because of cards like Overwhelming Splendor or abilities like Split second.

Other answers had good information, but I chose this one because it described specific cases where treating morph as a cost would break the way morph actually works.

Morph has a cost, but it is not a cost. It is simply an action you can take, like playing a land. You can think of turning a creature face-up in the same way as playing a land... playing a land has a cost of losing the land card from your hand; turning a creature face-up has whatever cost is listed next to the keyword "morph".
Normally the comprehensive rules are not a good way to go about learning or teaching the game, but the rules for turning a morph creature face-up are pretty simple here:

702.36e Any time you have priority, you may turn a face-down permanent you control with a morph ability face up. This is a special action; it doesn’t use the stack (see rule 116). To do this, show all players what the permanent’s morph cost would be if it were face up, pay that cost, then turn the permanent face up. (If the permanent wouldn’t have a morph cost if it were face up, it can’t be turned face up this way.) [...]

The fact that it can't be responded to and the fact that paying a cost can't be responded to are really the only 2 things that these have in common. Paying a cost when activating an ability is something you do in order to do something, in this case to activate the ability. The problem with looking at turning a morph card face-up as a cost is that there is no thing that you are paying the cost for. Turning it face-up is generally the end goal; not a cost you are paying to get to some goal.

As you (and the other answers) point out, being turned face up is not part of the cost. However, I do believe that is a reasonable approximation for teaching new players for the reasons you point out and one other that I can think of:
It is a pre-requisite to performing the action. By this I mean you cannot morph an already face up creature, or pay to morph a creature multiple times in succession, just as you cannot sacrifice the same creature to multiple sacrifice a creature costs.
Caveat
The one caveat I would give is be careful how you state that, you describe it as:

[Cost], turn this creature face up: Do nothing.

When I'm helping new players learn magic, I usually re-inforce that anything with a colon is an activated ability with the cost on the left and the effect on the right. Morphing not only does not use the stack, but also is not an activated ability. So, for example, a static effect on the creature that says activated abilities cannot be activated (such as being detained or under the effect of Arrest) would not prevent the creature from morphing.
Alternative
Instead of describing being turned face up as part of the cost of morphing, you could compare it to playing a land at instant speed. Both are special actions so exactly the same rules would apply, and it may be one less thing to keep track of.

Morph does not use the stack, which is why it seems to be part of the cost, but it is still in fact the effect of paying the morph cost. It's similar to how you can't respond to mana abilities, as they too don't use the stack. I would say explaining the cases that are independent of the stack would be the best way to show new players how these things work.
In reality paying a morph cost is ending a continuing effect, namely the card being face down as a result of being played morphed.

Paying a morph cost is not directly ending a continuous effect. It is its own special action that has multiple results, including ending a continuous effect.

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text:
Can I target any number of creatures, even if the ability would have no effect?
Aurelia's Fury and other spells like it allow me to choose any number of targets. As written, it implies I can choose more than X targets.
Can I, for instance, cast Aurelia's Fury where X = 5 and target 5 of my opponent's creatures, as well as all of my heroic creatures, and then choose to deal one damage to each of my opponent's creatures (leaving my creatures unharmed)? Or am I required to choose targets in some way such that the spell affects them (if possible)?

No.

601.2d If the spell requires the player to divide or distribute an effect (such as damage or counters) among one or more targets, the player announces the division. Each of these targets must receive at least one of whatever is being divided.

This is also mentioned in the Gatherer rulings for Aurelia's Fury:

You announce the value of X and how the damage will be divided as part of casting Aurelia’s Fury. Each chosen target must receive at least 1 damage.

Could you cast Aurelia's Fury with X = 0 just for the sake of targeting all of your own Heroic creatures and not dealing any damage to any of them?

You cannot.  If you are dealing 0 damage, then you choose 0 targets because of the ruling mentioned above.

You could cast it for X=0, but it would be an untargetted spell at that point and do nothing when it resolves.

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text:
Does Adarkar Valkyrie's ability target cards in graveyard?
Adarkar Valkyrie's third ability targets a creature and creates a delayed triggered ability that returns that creature to the battlefield when it dies this turn. It clearly targets the creature on the battlefield to create the delayed trigger.
Does that triggered ability also target the card that goes to the graveyard?
For example, does Ground Seal prevent the trigger from resolving?

Adarkar Valkyrie's ability does not target anything in the graveyard.
As mentioned in the question, the activated ability clearly targets a creature on the battlefield using the phrase "target creature". That creates a triggered ability that effectively says

When (that creature) dies, return that card to the battlefield under your control.

The creature that the trigger condition checks is fixed as the activated ability resolves. It is not a target that you choose while putting the triggered ability on the stack.

It doesn't 'check' the target twice, the same way that some spells and abilities check legal targets once upon casting/activating and again upon resolving?

The activated ability is what has the target, and that target is checked twice as you describe. It then creates a delayed triggered ability that doesn't have a target.

I have modified my last paragraph to try to explain this better.


text:
Sedris and Nicol Bolas, the Ravager
If I unearth Nicol Bolas, the Ravager thanks to Sedris, the Traitor King, then use Nicol Bolas's activated ability to exile it, does it return to the battlefield transformed?
Unearth seems to replace where it goes when it leaves the battlefield, but it's already going into exile.

Yes, Nicol Bolas will be exiled and return transformed. The Unearth effect does not apply to that event.
Sedris, the Traitor King has the following ruling:

If a creature returned to the battlefield with unearth would leave the battlefield for any reason, it’s exiled instead — unless the spell or ability that’s causing the creature to leave the battlefield is actually trying to exile it! In that case, it succeeds at exiling it. If it later returns the creature card to the battlefield (as Oblivion Ring or Flickerwisp might, for example), the creature card will return to the battlefield as a new object with no relation to its previous existence. The unearth effect will no longer apply to it.

The exact definition of Unearth is in rule 702.83a:

Unearth is an activated ability that functions while the card with unearth is in a graveyard. “Unearth [cost]” means “[Cost]: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step. If it would leave the battlefield, exile it instead of putting it anywhere else. Activate this ability only any time you could cast a sorcery.”

It is not going "anywhere else", so the Unearth replacement effect does not apply.

Nicol Bolas will be exiled and not return. Unearth doesn't care where the creature is going.
Unearth is a replacement effect. The event it replaces never happens:

614.1a Effects that use the word “instead” are replacement effects. Most replacement effects use the word “instead” to indicate what events will be replaced with other events.
614.6. If an event is replaced, it never happens. [..]

The event to be replaced is "Exile Nicol Bolas, then return him to the battlefield transformed". Exiling NB would cause him to leave the battlefield, so Unearth replaces the whole event and what happens instead is simply "Exile Nicol Bolas". Exiling Nicol Bolas this way does not return him, because the "return NB to the battlefield transformed" effect doesn't come from a triggered ability, it was part of the event that was replaced.

This is directly contradicted by a ruling on Sedris on Gatherer. See the other answer for the precise quote.


text:
Volrath's Shapeshifter, Static Buffs, and Combat damage
Inspired by this question.
I have an Elvish Archdruid, a Volrath's Shapeshifter, and a Llanowar Elves on the battlefield.
I attack with Elvish Archdruid and Llanowar Elves. My opponent blocks in such a way that Elvish Archdruid takes 2 combat damage and Llanowar Elves takes 1 combat damage.
Does the Llanowar Elves survive through combat?

Assuming nothing other than what is described happens (no first strike, no destruction spells cast, etc.), then yes, the Llanowar Elf will survive.
After combat damage has been dealt, but before any players have an opportunity to play spells, State-Based Actions are checked. The Archdruid is "marked" as having received lethal damage and is to be destroyed. The Llanowar Elf has not received lethal damage, and is therefore not marked for destruction. Then all applicable SBA are performed, meaning the Archdruid is actually destroyed.
Then SBA are checked again. This time, the Archdruid is on top of the graveyard, so the Shapeshifter boosts other elfs. So the Llanowar Elf is again 2/2, and has therefore not received lethal damage. It is therefore not marked for destruction. So when the SBA are performed, nothing happens.
At this point the SBA didn't change the game state, so they are considered finished, and the game continues on to letting players put on the stack any triggered abilities that may have triggered since before the combat damage was dealt. If any triggered abilities were put on the stack, SBA are again checked, and if any of them happen, then triggered abilities are once again put on the stack. And so on, until there are neither any SBA nor triggered abilities left to put on the stack. Then, for the first time, does the active (attacking) player get priority and can activate abilities and cast (instant / flash) spells.
There is no checking for lethal damage "between" the Archdruid boosting the Llanowar Elf, and the Shapeshifter doing the same.


text:
Can I target my own planeswalker with Angrath?
Angrath, Minotaur Pirate's oracle text for its +2 ability is different from its card text to differentiate 'opponent' versus 'opponent or planeswalker an opponent controls'.
Can Angrath target a planeswalker its controller controls with its +2?
I assume so, but the ruling on gatherer leaves me confused:

Angrath’s first and last abilities target only the player. Creatures with hexproof that player controls will be affected.

Yes, Angrath can target a planeswalker.  As you've stated the Oracle text for it's ability reads:

+2: Angrath, Minotaur Pirate deals 1 damage to target opponent or planeswalker and each creature that player or that planeswalker's
  controller controls.

Since it specifically says you can target a planeswalker, you can do so.  The Oracle text changed with the Dominaria rules changes to remove the planeswalker damage redirect rule.  Basically, you used to be able to target a player and redirect the damage to their planeswalker.  Now Wizard's is explicit about when you can damage planeswalkers.
The ruling you see on the gatherer page is likely a leftover from before the Dominaria rules change (when you would have just targeted the player rather than the planeswalker).  The ruling appears to be trying to clarify that even if your opponent's creatures have hexproof they will still get damaged (since the creature itself is not the target of the ability hexproof doesn't apply).  It should probably be cleaned up to state that the ability targets only the player or planeswalker.

Edit to address the explicit question in the post.
You can target your own planeswalker if you would like.  The Dominaria rules update states:

Abilities that damage "target opponent" have been changed to "target
  opponent or planeswalker" with the same exception listed above. These
  spells and abilities can target a planeswalker you control.

Does not actually answer the question - which asks if they are restricted to targeting a planeswalker their opponent controls or if they could target their own planeswalker, say Angrath himself. Your answer says nothing about who controls the walker, just if a walker can be targeted, which was accepted in the premise of the question.

@Andrew I agree that that is the question that was asked in the text, but I'm inclined to think that maybe they meant something else since they quoted a ruling about targeting players rather than planeswalkers.  (I had to reread this morning to figure out what you were talking about, so in hindsight I probably should have asked for clarification.)

@Andrew Also edited to answer the question that was explicitly asked.

Yes, there's no restriction on the effect for which planeswalkers can be targeted, you could use that +2 to even target Angrath himself, doing 1 damage to that walker and every creature you controlled.
As Becuzz said this change is due to the removal of redirected damage from player to planeswalker, originally the player would be targeted and damage redirected, now planeswalkers must be specifically listed as targetable, or the target be general enough to include them, as in "any target" effects. With the original rules and ability you would not have been able to target planeswalkers you control with your own Angrath.
This was mentioned specifically in the Dominaria update bulletin:

Abilities that damage "target opponent" have been changed to "target opponent or planeswalker" with the same exception listed above. These spells and abilities can target a planeswalker you control.

According to the Dominaria update bulletin, this change was very much intended. Changing "target opponent" to "target opponent or planeswalker" was one of the standard changes that was applied to every relevant card. The ruling is clearly just left over from before that change.

@murgatroid99 I hadnt seen that, ill edit that part out.

I also recommend rewording the first sentence. For me, the intermediate clauses make it a little hard to follow exactly what the answer is. I suggest starting with something like "Yes, you can target any planeswalker, even one you control" and then follow that up with details about the ability wording and the fact that you can even target Angrath.


text:
Can players respond before vehicles are declared as blockers?
My question concerns players receiving priority.
My opponent has a Void Stalker, and attacks with a flying creature. I have a creature with protection from blue and a flying vehicle. During the declare blockers step, I crew my vehicle.
Is there a time between me crewing my vehicle and declaring it as a blocker where my opponent could void stalker's ability to shuffle my vehicle back into my deck?

Yes, your opponent can respond.
When you activate your vehicle's ability, the ability will go on the stack.

117.4. If all players pass in succession (that is, if all players pass without taking any actions in between passing), the spell or ability on top of the stack resolves or, if the stack is empty, the phase or step ends.

Once all players pass, the ability will resolve.  Then players recieve priority again, and you won't move to the Declare Blockers step until all players have passed priority.
As a side note, if you are crewing your vehicle in the Declare Blockers step, you're doing it too late.  The action of declaring attackers or declaring blockers is the first thing that happens in that step, and you recieve priority afterwards.

@ikegami, to block with a vehicle, the best time to activate it is typically the declare attackers step, which is the priority between declaring attackers and blockers.


text:
What is the origin of the term 'Mana Dork'?
'Mana Dork', as a slang term, refers to a creature that taps to produce mana, such as a Llanowar Elves.
What is the origin of this name? If someone simply started saying it, do we know who first popularized it?

The oldest reference I can find for this kind of usage of the term "dork" is an event coverage article on the Wizards website apparently dated January 1, 2000. It contains this description:

"dorks" - creatures that are "ok" but not "savage"

This may be establishing the use of this word in this way, or it may just be explaining the usage.
The oldest reference I can find for "mana dork" is this MTGSalvation Forum post dated August 29, 2005. So, it seems likely that "dork" came first, and a "mana dork" is just a "dork" that produces mana.

I think the definition of a dork can be beneficial in our attempt to dissect the language usage.

dork NOUN
North American informal A contemptible, socially inept person.

Often the imagery conquered up is that a dork is a creature to inept to attack, but still useful in other ways. A mana dork is a variation on this theme being an inept creature that is used to ramp into other things.
This concept of a dork is rather ironic now because playing a turn 1 mana dork is such a power play in modern that you are almost forced to kill the dork before your opponent gets to untap with it. Giving rise to the phrase... 'bolt the bird'. Which is a colloquialism for using a lightning bolt to kill birds of paradise?
I remember Brad Nelson discussing the topic that when green decks in standard are allowed to untap with there elvish mystic then their chances of winning the game goes up by anything between 20 - 40 percent.
RD has realised that this is a bit more variance than they wanted one card to have and will only selectively allow one-mana, mana dorks in standard or when it is thematically appropriate (Like the printing of Llanowar Elves in Dominaria).


text:
How to interrupt a loop with multiple players?
Assume there are three players, Alice, Bob, and Chris. The turn order is Alice, then Bob, then Chris, with it currently being Alice's turn.
Alice has a loop that can infinitely create creatures, two creatures on the field, and 20 life.
Bob has a Leyline of Anticipation on the field and a Deadly Tempest, and is planning on casting it when Alice has twenty creatures on the field to deal 20 damage to her.
Chris has a Fumigate in hand and plans to use it on his turn to gain a lot of life and clear the board. Chris also has a Soul Warden and an Aethersphere Harvester on the field.
Alice proposes a shortcut to do her loop a hundred times. Bob wants there to be at least 20 creatures on Alice's board (but wants to minimize this number to minimize how much life gain Chris's Soul Warden gains him), so he proposes to stop at only eighteen loops. If Chris weren't in the game, Alice would be required to accept this new loop (despite the fact that she just got information about Bob's plan). However, Chris and Alice both want Alice to stay alive (at least for now), so Chris proposes only seventeen loops (after which he uses Soul Warden to crew Aethersphere Harvester). Crewing the vehicle does nothing to stop Alice from resuming her combo, but both players just got information about Bob's hand, which causes her to not put another creature on the field.
Is this legal, or does Chris have to provide some kind of 'legitimate response' to interact with Alice's loop, other than the fact that Bob gave away information by proposing a stop to the loop?
Edit: Or is my understanding of the order in which players propose shortcuts wrong?

The described situation is perfectly legal. These loops are governed by rule 720, concerning the taking of shortcuts.
CR720.2a, b and c explain how shortcuts are to be taken:

720.2a At any point in the game, the player with priority may suggest a shortcut by describing a sequence of game choices, for all players, that may be legally taken based on the current game state and the predictable results of the sequence of choices. This sequence may be a non-repetitive series of choices, a loop that repeats a specified number of times, multiple loops, or nested loops, and may even cross multiple turns. It can’t include conditional actions, where the outcome of a game event determines the next action a player takes. The ending point of this sequence must be a place where a player has priority, though it need not be the player proposing the shortcut.
720.2b Each other player, in turn order starting after the player who suggested the shortcut, may either accept the proposed sequence, or shorten it by naming a place where they will make a game choice that’s different than what’s been proposed. (The player doesn’t need to specify at this time what the new choice will be.) This place becomes the new ending point of the proposed sequence.
720.2c Once the last player has either accepted or shortened the shortcut proposal, the shortcut is taken. The game advances to the last proposed ending point, with all game choices contained in the shortcut proposal having been taken. If the shortcut was shortened from the original proposal, the player who now has priority must make a different game choice than what was originally proposed for that player.

Notice the emphasized sentence: that player, in your situation, is Chris. Since Chris was the one who suggested the fewest number of iterations for Alice's loop, when he receives priority, he must take an action that is different from the action originally proposed by Alice for the shortcut.
As you can see, as long as it is a different action from the one originally proposed, it doesn't matter what action that is. Once that action (in your case, crewing the Aethersphere Harverster) has been taken, play continues normally in turn order. Alice can then propose a new shortcut to continue her loop if she wishes to do so, but that action is not required.


text:
Do I know which card an opponent revealed?
When an opponent reveals a card in their hand, are players supposed to know when that card changes zones?
My instinct says no because

400.5. The order of objects in a library, in a graveyard, or on the stack can’t be changed except when effects or rules allow it. The same is true for objects arranged in face-down piles in other zones. Other objects in other zones can be arranged however their owners wish, although who controls those objects, whether they’re tapped or flipped, and what other objects are attached to them must remain clear to all players.

However, rearranging objects doesn't necessarily mean making your opponent lose track of them. In MTG Arena, a card revealed is shown face up in your opponent's hand at all times. Thus, you know if the card leaves their hand. A good practical example of this mattering might be:
Your opponent returns shock from their graveyard to their hand. Later, they draw one or more cards, then cast shock. They either A) cast the shock that was revealed, or B) drew another shock and cast it.
A savvy player will probably cast the one that was revealed, but some players may accidentally cast the recently drawn one instead. In MTG Arena, I would know if this is the case, because there would be a shock on the stack, and a shock card revealed in their hand.
In normal Magic, is there supposed to be a way of remembering which one the revealed card is? Or is this a place where the gameplay of MTG Arena differs from regular MTG?

Hi, I wouldn't want to write a formal answer without testing and citations, but my experience has been if you have two identical copies of a card on Arena where one has the eyeball on it and cast the one that wasn't revealed, the eyeball is removed from the one that had been revealed.  So if you cast the "wrong" one, I believe the client corrects for your mistake and is in line with paper.  Now, if you have two different versions of the card (one is M19 and one is M20), then they will know about both (which is also true to real life, although maybe harder to catch in paper).

Wait, really? But if the revealed card suddenly flips over when my opponent draws a card, doesn't that kind of tell me exactly what they drew?

402.3 is better than 400.5 for your question.... but even though I'm almost sure your instinct is correct; I cannot find a comprehensive rule to back it up.

True. Although 'arrange' still doesn't imply that your opponent doesn't know the new arrangement. I can 'arrange' my various morph cards on the battlefield as I like, but which one is which still has to be known to players. The difference is morph specifically calls out that requirement whereas cards in hand doesn't say anything about that.

This question has similar ideas discussed https://boardgames.stackexchange.com/questions/23937/am-i-allowed-to-shuffle-my-hand-when-ever-i-want/23944#comment32050_23944

@Aetherfox the morph part still completely confuses me. Let's say my opponent has 1 card, i look at it and see a morph creature. Next turn he draws a card, and plays a creature morphed, do i know if it was the old card or the new card? In Arena (if morph existed) I would. In paper reading these answers, I would not

@Andrey I don't think it would work like that.  I think it would behave as if you could have drawn another morph card, and no cards would be revealed anymore.  I'm not sure, but I don't think it would even be complex enough that even if you later saw their hand and confirmed that there were no more Morphs that suddenly it would confirm the morph.  I guess we could test a similar situation.  Reveal a card due to something, then use a Brainstorm effect (like blue Cavalier), then draw those two cards again.  I wonder if after you draw the second it will reveal them again.

Corner case: your opponent controls a Sylvan Library...

You only know a revealed card for the duration that it remains revealed.
The example of Shock moving from the graveyard to the hand is a bit nuanced (since the card isn't technically revealed, mechanically), so I'm going to start with a more direct representation of the question and move from there. Let's say you cast a card like Thoughtseize which causes your opponent to reveal their hand. In MTG Arena, this is represented by the game revealing all of those cards to you from that point onward. However, that's not quite feasible in paper Magic - in the vast majority of cases, you'll pick a card for your opponent to discard, and then they'll go back to holding their hand towards themselves. That is, even though the information was revealed to you, by default you don't continue to be able to see those cards. It would be impractical for the opponent to hold newly drawn cards in their hand and simultaneously have those previously revealed cards lying on the table, for example. The information is known, but it's up to you to remember what that information was.
When I was playing Standard regularly (circa Theros) and my opponents cast Thoughtseize targeting me, I would show my opponent my hand, and they would use a notepad to write down the cards that they saw. Later, as I played those cards, they would scratch off the name of the card that I played if it was in that list. This, I believe, is what the functionality of MTG Arena seeks to emulate. Knowing that information was revealed to you, but misremembering it, feels bad. Arena can leverage its nature as a computer game to assist you with that, by making sure that you don't forget what cards were revealed. (There are other aspects it helps you with, too -- in real life, the cards you can cast don't glow.)
Rule-wise, of particular interest are the rules for revealing cards:

701.15a To reveal a card, show that card to all players for a brief time. If an effect causes a card to be revealed, it remains revealed
  for as long as necessary to complete the parts of the effect that card
  is relevant to. If the cost to cast a spell or
  activate an ability includes revealing a card, the card remains
  revealed from the time the spell or ability is announced until the
  time it leaves the stack. If revealing a card causes a
  triggered ability to trigger, the card remains revealed until that
  triggered ability leaves the stack. If that ability isn’t put onto the
  stack the next time a player would receive priority, the card ceases
  to be revealed.
701.15b Revealing a card doesn’t cause it to leave the zone it’s in.
701.15c If cards in a player’s library are shuffled or otherwise reordered, any revealed cards that are reordered stop being revealed
  and become new objects.

The phrasing of 701.15a makes it pretty clear that a revealed card is only revealed for a short amount of time, and then ceases to be a revealed card. You know what the card is because it was revealed, and can do whatever you want with that information (such as write it down), but it doesn't stay revealed after that. By extension, cards moving from a public zone to a hidden zone (rule 400.2) work very much the same way. Everyone is allowed to know what that card is as it moves into the zone, but after that, it becomes hidden.
Some relevant excerpts from Rule 400 regarding public and hidden zones:

400.2 Public zones are zones in which all players can see the cards’ faces, except for those cards that some rule or effect specifically
  allow to be face down. Graveyard, battlefield, stack, exile, ante, and
  command are public zones. Hidden zones are zones in which not all
  players can be expected to see the cards’ faces. Library and hand are
  hidden zones, even if all the cards in one such zone happen to be
  revealed.
[...]
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.

To use your example, let's say your opponent uses Call to Mind to return Shock from their graveyard to their hand. During the announcement of the spell (rule 601.2c), they would choose the target for it - Shock. Because the card is targeted, everyone inside and outside the game knows which spell is going back to their hand. As soon as Call to Mind resolves, the Shock is moved to their hand, where it becomes hidden along with all the other cards they hold. You know what card it is, but it is now part of a hidden zone, and there are no other effects requiring the card to remain revealed. You don't get to see it once it's back in their hand.

I agree with what you're saying here, but by my reading the question is less about whether a card stays revealed after the reveal effect ends, and more about whether the opponent is entitled to know which physical card in the hand was previously revealed, and I don't think you really address that here.

Once a card stops being revealed, it should be considered indistinguishable from the rest of the hand. There is no direct rule that states this, but various rules imply that non-visible cards in hand should be considered indistinguishable or interchangeable. Rule 402.3 says

A player may arrange their hand in any convenient fashion and look at it at any time. A player can’t look at the cards in another player’s hand but may count those cards at any time.

and rule 400.5 quoted in the question also supports that interpretation.
In addition, we can look at the behavior of official game implementations to infer what the intended interpretation is. In Magic Online, cards that are revealed from any zone are added to the "revealed cards" (pseudo-)zone. Players are responsible for keeping track of which cards were revealed from which zones, and when those cards leave those zones.
I am having trouble finding a complete description of how exactly Magic Arena handles revealed cards, but there are simple ways of implementing it that are both consistent with the observations in the question and consistent with this interpretation. For example, Arena may remove a card from the revealed cards display whenever a card of the same name (or appearance) moves from that hand to a public zone.

As per the original poster, I'm pretty sure that in Arena if: 1) you have two cards of the same name in your hand 2) one of them has been revealed and the other hasn't 3) you play the non-revealed one, then the revealed one remains revealed. I'm trying to work out an easy way to test this against Sparky (the Arena bot) but can't think of an obvious one. Anyone who wants to fire a Duress or something against me in a direct challenge, ping me in chat.

I'll test this later tonight.  I have a deck which runs Growth-Chamber Guardian, and annoyingly you always draw duplicates of that card.  I believe I have accidentally played the naturally drawn copy in a game and the eyeball on the searched copy vanished, but I want to verify for certain.  Also, I do want to mention that the name of the card does not matter.  I know it has to be the same set/art, or they are definitely treated as distinct cards.

Verification of both of those would be helpful. I said "name" because the standard in Magic is to treat card with the same name as the same, but for this specific scenario treating different arts as different makes sense.

Yeah, I checked this several times last night.  Like @Allure said, if you have two absolutely identical cards where one is revealed, and you play the one that is not marked as revealed then it removes the revealed mark from the other.  Now, if you have alternate versions of the card then this doesn't happen (they saw an Island with Thought Erasure, you play a different art Island you just drew, the other Island is still marked).


text:
When is the last time tribal decks were competitive?
More or less what it says on the tin. I see a lot of meta decks that revolve more on a (thematically) random group of cards that only share a strategy.
When is the last time a tribal deck was competitively viable in Standard? (Let's say, the last time a tribal deck made it into the top 4 at a major M:TG tournament.) What tribe was it?
Was there ever a time when tribal decks dominated the Standard meta?

How do you delineate between "tribal" and "random group of cards that only share a strategy"?  Orzhov Vampires/Aggro is a thing right now.  There were some dinosaur decks that did well earlier this year.  Do those count as "tribal"?  (For reference I was using mtgtop8.com to find some of these.  See here and here for example)

My metric is 'core cards in the deck care about a certain creature type'. Whether that's buffing them, fetching them, or doing something based on having them. Thanks, I wasn't aware of mtgtop8 as a resource! (Just now getting into mtg competitive scene)

Grand Prix Denver 2019, 4th place: Orzhov Vampires. All 26 creatures, the 4 Sorins and Legion's Landing are all vampire themed.

If you consider "Tribal decks" as decks with

core cards in the deck [that] care about a certain creature type,

there's plenty of examples out there.
This will be a very broad answer that'll brush over many specifics of the metagame and the differences between physical and digital plays, focusing only on information available from resources such as MTGTop8, which accounts mostly for MTGO tournaments.
In the current (as of 09/09/19) standard meta, Orzhov Vampires represent 11% of the (MTGO) field, while Jund Dinosaurs represent about ~5%.
Both of those decks focus on aggressively dishing out their creatures and hitting for as much damage as possible, using those same creatures to create card advantage (such as Champion of the Dusk and Ripjaw Raptor), or decrease the clock to end the match more swiftly (such as Legion Lieutenant, Sanctum Seeker, Marauding Raptor and Rampaging Ferocidon).
Both these decks are currently posting good results consistently in standard play, as you can see from the links provided.

When talking about Modern, the obvious examples are 5 Color Humans which focus on Human creatures, while some Eldrazi variants focus on Eldrazi creatures and fast mana. It's also worth mentioning the Spirits deck, which focuses on Spirits. All three of these currently post good results in the modern metagame, although they're not as dominant as they once were, especially the eldrazi decks.

Legacy has always had some tribal decks being represented, although not many with expressive results. The currently most represented tribal decks are Goblins, Humans and Slivers, although they're only about ~4% of the whole Legacy field, which favours more controlling and combo decks due to faster mana and cheaper countermagic.
As @Veskah noted, Elves has been very represented in Legacy at some point, but its power has dwindled lately due to the more controlling meta for the format. That said, Elves is one of the original tribal decks in Legacy, and it veers from the usual strategy by being something of a combo deck, relying on generating huge amounts of mana and putting many creatures on the board to finish the game with a Progenitus or a Craterhoof Behemoth.

Vintage has also has some tribal decks in the meta for a while, specifically Fish, which used to be Merfolk tribal decks, although today the term has been adapted to mean any kind of (mainly blue) deck with cheap creatures and lots of countermagic. Along with Fish comes the ever-present Eldrazi, although once again it's more of a hate/control deck than an actual tribal deck.

Aw, Elves not even getting a shout-out despite being one of the OG tribes?

@Veskah I guess I skipped over elves mostly because it's considered a combo deck while usual tribal decks are aggro. It's definitely worth a mention though, so I'll add it to the answer.


text:
When and which board game was the first to be ever invented?
Which board game is the first to be ever invented, when was it invented and where?

You might have to specify some criteria on what counts as a board game.

What is a game recommendation question? Anything where you're asking for answers providing a (set of) games meeting the criteria in the question.

@Thunderforge you're right the definition is vague, but for me a board game is '"a game that involves the movement of counters or other objects round a board.'", basically you must have a board for it to be a board game. But you're right, this is a bit vague definition. PS: Wow +60 rep, thank you all)

@Harold_Ed Why does a Boardgame need to have a board?  eg Carcassone.

@StartPlayer : shrug : - fair question, i was biased when making that comment

This academic paper makes a strong claim for Three Men's Morris (later to become Nine Men's Morris; the game is generalised to 'merels' in the paper); it may be that some Stone Age or Bronze Age petroglyphs were boards scratched on boulders near houses. R.C Bell, in Board Games from Many Civilizations, claimed that a Three Men's Morris board was scratched into an Egyptian temple about 1400 BC, but it is fair to say this is not universally accepted.
Of course, the definition of a board game is somewhat vague. One petroglyph was apparently used in adjudicating 'court cases'; each side threw a stone over their shoulder and tried to hit the design, with the closer to the centre being approved by the gods, so deemed to be telling the truth. This is no longer used in jurisprudence (to the best of my knowledge), but could be considered a game...

"each side threw a stone over their shoulder and tried to hit the design, with the closer to the centre being approved by the gods, so deemed to be telling the truth". This sounds like how a number of cultures viewed archery as a measure of one's virtue, but it's typically not considered to be a game. I think there's an implied assumption that a "game" is a measure of skill or luck, not external forces.

According to oldest.org, the oldest board game was Senet, invented ca. 3500 BCE in Egypt.
Some other ancient games that are popular are Checkers (c.3000 BCE, Ancient Mesopotamia), Go (c.c.2000 BCE, Ancient China) and Chess (c.600 AD, India or China)

The oldest games that could be considered "board" games are almost certainly of the Mancala family.
Mancala pieces have been found throughout Africa (including Egypt) and The Middle East to dating all the way back past 6000 BCE, with the earliest potential Mancala board (Fig A) coming from ~7-6500 BCE at ʿAin Ghazal, but it's possible that two rows of divots were carved into a stone for an unrelated reason.
Note: Fig B. below is from Qal’at al-Bahrain, and dates from ~3-3500 BCE.

And therein lies the main issue with dating when and where Mancala style games first developed, as a rudimentary board can be made by simply digging a number of holes in the ground, and collecting random items from the surrounding area as playing pieces (shells are a popular option).
The simplicity of board creation also leads to a secondary issue with dating Mancala's origins, as even when the surrounding materials can be dated, a board can easily have been carved much more recently by later occupants; an example of this is the board found on the roof of the temple of Seti I (1290–1279 BCE) in Egypt, which was most likely carved by priests using the temple roof for astronomy sometime after construction.

Not to forget Backgammon which is supposed to be one of the oldest games in existence. Around 5000 years ago it appeared in the Mesopotamian area. Until today experts are not sure if that was really a backgammon game or a distant relative or even a completely different game. The fact is that there was a board game in ancient Persia that was at least similar to our backgammon. From there, the game probably came to India and Egypt - in exchange for another time-honored game: chess. Archaeologists also unearthed a backgammon-like game board in the lost Mesopotamian metropolis Ur.

This is 500 years after what another answer for the oldest game.

I assume it is difficult to give a precise answer on the question. And the answer you refer to says ca. 3500 BC not exactly 3500 BC. Backgammon is from my perspective definitely worth to be mentioned here.

Backgammon would be from around 3000 BC which is still long enough after the other answer to be unlikely developed before it.


text:
In reversi, can you overwrite two chips in one move?
In Reversi if you have a line of chips --xxxy--, you can place another x in the 5th position and overwrite the y you for sure can get the line --xxxxx- (where x is light, y is dark, and - is empty, line may be horizontal, vertical or main diagonal).
Can you do the same if the line contains one (or more) enemy chip in between? If you for example have -xxyxyx-, can you get -xxxxxxx?

No. From the Rules of Play:

Each piece played must be laid adjacent to an opponent's piece

so that the opponent's piece or a row of opponent's pieces is flanked by the new piece and another piece of the player's colour.

All of the opponent's pieces between these two pieces are 'captured' and turned over to match the player's colour.

where I have split up and numbered the clauses of the paragraph for easier reference.
Note that:

from (1), the suggested move is illegal, not being adjacent to an opposing piece;
even if one is playing to make -xxyxy-- into -xxyxyx-, by (3) only the second 'y' is flipped, resulting in -xxyxxx- upon completion of the move; and
playing to make -xxxyy-- into -xxxyyx- does convert multiple opposing counters, by (2) and (3), flipping to yield -xxxxxx- upon completion of the move.
Reason:
"All of the opponent's pieces between the these two pieces [(the just placed piece and the enabling friendly piece at the far end of the just surrounded enemy row of pieces)] are 'captured' and turned over to match the player's colour."

What about a case like XYY-YYX where an X is played in the center? Ignoring for the moment whether such a board scenario is possible, I would think that it would flip all the Ys as two separate lines can be drawn from the move coordinate: one to the left and one to the right. If not, what is the precedence when this is generalized to 2 dimensions? Say you have a move that would draw a line up and down-right, for example.

My expectation was correct


text:
What card game was played in "Solo: A Star Wars Story"?
Han Solo won the Millennium Falcon at the end by playing a card game. What game was that actually?

The card game is called Corellian Spike, a variation of sabacc.


text:
Should the barrel being discarded when hit - Bang
In case the barrel card get hit and accomplish his goal, is it supposed to be discarded or not?
Same question, in case the barrel doesn't get hit, can be used to face further bangs?

As you can see in this answer on BGG, the barrel stays until it is removed by another card.
Also, from the official rules:

Blue-bordered cards are played face up in front of  you  (exception: Jail).  Blue  cards  in  front  of you are hence defined to be “in play”. The effect of  these  cards  lasts  until  they  are  discarded  or removed somehow (e.g. through the play of a Cat Balou), or a special event occurs (e.g. in the case of Dynamite). There is no limit  on  the  cards  you  can  have  in  front  of  you  provided  that  they  do  not share the same name.

The Barrel is a blue card. So you can use it as long as it is on your side of the table.

Can you change the following text please? an other -> another; offical -> official


text:
Effects depending on an impossible effect?
Sometimes, when a spell or ability resolves, part of what it does is impossible to do. In these cases, the following rule applies:

609.3. If an effect attempts to do something impossible, it does only as much as possible.

I understand that. But what if some effects on the card depend on what you did, when you didn't do what you couldn't do. Most of these effects will not do anything, because you cannot do anything with a card you couldn't reveal from an empty library. But some have effects that you could still perform.
An example: Merfolk Branchwalker reads:

When Merfolk Branchwalker enters the battlefield, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)

So what if this effects resolves, when you have an empty library? Obviously no card is not a land card, but is the +1/+1 counter put on it? Or is this effect just skipped because it depends on an effect that could not be done? What about cards that care about any values (cmc, power,...) the card has? Are they just interpreted as 0?
Some other examples include Counterbalance and Candles of Leng. There might be examples outside of effects that affect the top of your library, but I didn't find any unclear ones.

If a creature explores an empty library, the creature gets a +1/+1 counter and nothing more happens. There is no general answer to what happens with multiple, partially impossible instructions.
The relevant rules of the explore mechanic are:

701.39a Certain abilities instruct a permanent to explore. To do so, that permanent’s controller reveals the top card of their library. If a land card is revealed this way, that player puts that card into their hand. Otherwise, that player puts a +1/+1 counter on the exploring permanent and may put the revealed card into their graveyard.

You can't reveal a card because there are none remaining in the library. Therefore, no land card has been revealed, so you can't put it in your hand and you continue resolving the ability with the "otherwise" instructions. Note that the "otherwise" condition refers to both the "card" and "card type: land" requirements that both have to be true to make you take the first branch of the instructions.
In the second branch, you do as much as possible: You put a +1/+1 counter on the creature and, since you didn't reveal a card, can't choose to put the revealed card into your graveyard, so nothing happens on that instruction.
It would have been possible to word the second branch so that the creature gets a counter if and only if you actually put a card into the graveyard, i.e. the creature would not get a counter on exploring an empty library. In that case, it would get another instruction branch nestled into the second branch:

Otherwise, you may put the revealed card into your graveyard. If you do, put a +1/+1 counter on this creature.

Because of the flexibility of the rules, it's impossible to give a general answer as to what happens when there are multiple instructions and some of them are impossible. It always depends on the wording of the card(s) involved.

Your modification of how this works would also change the way explore works usually. As I read your answer, it would also be possible to say:
" If a non-land card is revealed this way, put a +1/+1 counter on this creature. You may choose to put the revealed card into your graveyard."
Thereby only changing the way it works when you have an empty library. In general, it seems to me, that "if" clauses will usually be skipped, while "otherwise" clauses will usually be executed, so Counterbalance will not counter spells with cmc 0 on an empty library, am I right?

Your proposed modification to explore skips the part where you always put the card into your hand if it's a land. Looking at the general case in terms of "if" and "otherwise" is probably an oversimplification. In this case, the "if" condition is simply always false on an empty library, which always results in going to the "otherwise" case. In general, there may be all sorts of situations that make whatever "if" condition the card has guaranteed to be true or false; you have to consider the card's specific wording.

In the case of Counterbalance, the ability checks "If you do [reveal the top card of your library]", so if you don't do that for any reason, including your library being empty, the rest of the effect doesn't happen and nothing gets countered.


text:
Can another instant be used to buff an attacking creature, after another instant was cast that would kill the creature?
Specific example: Attacking player sends a 3/2. Defending player plays Shock to deal 2 damage to the creature. Attacking player then attempts to cast another Instant which would lend the attacking creature additional +/+.
I was under the impression the Shock would resolve first, and the attacking player can’t then buff a 3/0 creature since it would be dead.

There's an example of exactly this situation in the online rules ("Example of Spells on the Stack")


text:
I noticed after the last lead someone reneged but it actually helped me so I just let it go
I had made it spades I played the jack of clubs opponent put on the ace of clubs and I had low clubs but more and higher spades. If the gentleman had played properly he probably would have euchred me. So instead of trying to get 2 points when really played right they would of got the 2. But because he reneged and wasnt played right i might have got a point or i may have gotten euchred. We very seldom count a 2 points for reneg its either corrected. For a lone its counted as 4 points otherwise you could just reneg so person couldnt get their lone hand. He had the right bower when he reneged so i thought anyway i wasnt getting 2. Did I do the right thing to let it go?

Most Euchre rules leave it the opponent (you in this case) to call the renege. They don't explicitly identify it as optional, but neither do the penalty sections go on to say what to do if you don't call it (i.e., there's no penalty for not calling a renege).
For instance, from these rules:

the opposing team is rewarded two points if it is caught

and

[unintentional reneges] are still callable by opponents as reneging

(emphasis added)

The Laws of Rubber Bridge are more speccific: "Law 64 - Procedure after Establishment of a Revoke .... (D). ... When any established revoke, including one not
subject to penalty, causes damage to the non-offending side insufficiently compensated by the Law, the offending side should transfer additional tricks so as to restore equity.*"

Yeah, the bridge mindset is quite different.


text:
Reordering Static Effects with Dependencies on a Changing Board State
All of the discussion about Dryad of the Ilysian Grove's Layer 4 confusion and other discussions about continuous effects got me thinking about an unintuitive situation that can result from dependencies and seemingly unrelated changes to the board state.  Here is the scenario:

Player A controls some basic Forests, a Gingerbread Cabin and Life and Limb.  All of their Forests (including the Cabin) are 1/1 Saprolings.
Player B casts Blood Moon.  Life and Limb's ability is dependent on Blood Moon because it changes what it applies to (specifically, whether it applies to the Cabin).  As such, the Cabin becomes a Mountain when Blood Moon is applied, and does not become a Saproling when Life and Limb is applied.
Player A casts Sprout Swarm and creates a 1/1 Saproling token.  This now creates a dependency of Blood Moon on Life and Limb as now the application of Blood Moon to the token will depend on whether Life and Limb has been applied yet.  This forms a dependency loop as outlined in 613.7b-c.  We would apply Life and Limb first due to the timestamp order, then reevaluate and determine no further dependencies exist.  Then we would apply the effect from Blood Moon.  As such, both the Gingerbread Cabin and the Saproling token will have the stats of 1/1 green Land Creature -- Saproling Mountain.

So my question is about whether this is correct.  Can the presence or absence of an object with no static abilities of its own shake up the orders of these continuous effects in a meaningful enough way to determine whether a seemingly unrelated object will have effects applied to them?  Or am I missing or misunderstanding something that would not cause this unintuitive result?

Yes, the existence of an object with no abilities can change the order in which effects are applied.
In the section about dependencies, rule 613.7a says

An effect is said to “depend on” another if (a) it’s applied in the same layer (and, if applicable, sublayer) as the other effect (see rules 613.1 and 613.3); (b) applying the other would change the text or the existence of the first effect, what it applies to, or what it does to any of the things it applies to; and (c) neither effect is from a characteristic-defining ability or both effects are from characteristic-defining abilities. Otherwise, the effect is considered to be independent of the other effect.

The highlighted section clearly indicates that the dependency order of effects depends not only on the effects themselves and the objects those effects are on, but also the full set of objects that those affects could apply to. So a change to that set can change how effects are applied.
So, your description of how that example would play out is correct. The existence of the Saproling token changes the dependency order between Life and Limb and Blood Moon, which results in Gingerbread Cabin ending up with different characteristics.


text:
Where does Æmber captured from own side go after creature leaves play?
I've got a card (Mars Needs Æmber) that has the following play ability:

Play: Each damabed enemy non-Mars creature captures 1 Æmber from their own side.

I was wondering what happens when this creature leaves play? My interpretation of the rules would suggest that the Æmber would then go into the pool of the player who played the Mars Needs Æmber card. Is this right?

Yes.
From the rulebook (https://www.fantasyflightgames.com/en/products/keyforge/) page 6:
"When a creature leaves play, any Æmber on that creature is gained by the opponent."

No, but Yes!
It doesn't matter who played Mars Needs Æmber, all that matters is who controls the Martians when they leave play. There are a variety of effects that can temporarily gain control of a creature. Who the Æmber was captured from doesn't matter, only who controls the creature at the time it leaves play. Since Mars Needs Æmber doesn't deal damage, or remove creatures from play, once it's played, who played it is forgotten as far as the Æmber is concerned. This is a small, but important distinction!

captured Æmber always goes to the opponent of the card's owner when it leaves play, right?

Yes. In the exact situation you mention (with nothing else happening between) the answer is Yes...however it is important to remember that the Æmber goes to the opponent of the controller of the creature. Where it came from and who owns the creature are irrelevant.

My bad, I meant controller and not owner.

To be fair, usually the owner and controller are the same, the distinction is only important when someone is controlling one of their opponent's cards.


text:
Skip card - Phase 10
When playing phase 10, If I have a skip card in my hand and it’s my turn to play, do I have to pull a card before I play my skip card?

Yes.
The skip card does not have any special rules about when it can be played; you discard it the same way you play any other card; and it does something special when you do.

On your turn, draw one card, either the top card from the draw pile or the top card from the discard pile, and add it to your hand. End your turn by discarding any one of your cards onto the top of the discard pile.
SKIP CARDS: Skip cards have only one purpose: to cause
another player to lose a turn. To use, simply discard the “Skip” card on your turn, then choose the player who will lose a turn.

And note that if you did not draw before playing skip cards, your hand would become permanently smaller which could cause some phases to become impossible to complete (e.g. if you played two skips in phase 6, reducing your hand size to 8 so you could never get a run of 9).


text:
Why are Gatorbacks so expensive?
David Blaine's Gaterbacks sell easily at around the £20 mark. However, as far as I know, they aren't marked, they don't come with any gaff cards and other than the foil backs they aren't custom or even on a rare card-stock.
As a fairly new magician, I struggle to understand why such playing cards are as expensive as they are! Fontaine's are very limited, hence their price... are gaterbacks also very limited? What's so special about them?

I noticed there wasn't a forum for magic/ cardistry as well as a lack of tags relating to such things. Dear MODS if you must mark this as off topic, please tell me where I can post such a question.

https://www.investopedia.com/terms/v/veblen-good.asp

Simply because it is a name brand that focuses on quality. Looking at the official site they put an emphasis on quality and combine that with a very big and popular name brand you get a higher price.
Having to license the David Blaine name and brand is most likely very expensive and is why you see a higher price on many name brand products.

Damn, I hate having to pay for a brand name. Why can't we have cool cards that cost the same as bikes?? They basically cost the same to produce. Thanks for your answer!

@117Halo What do you mean by "cool cards"?  If you mean that you want to have the sar quality as bikes but in many different designs, they definitely do not cost the same.  Material is the same cost per deck but lower print runs and multiple die changes increases the manufacturing cost exponentially.


text:
How do I allocate variable damage to multi-wound models?
Let's say my grav cannons (D3 damage) shoot at some crisis suits (3 wounds each) and the suits fail 3 saves. I roll damage and get a one, a two and a three. Should I have rolled the dice in order? Or can I roll them together and allocate? Or do I roll them together and the other player allocates?
To see how different this could be:

If I allocate, I'll apply the three first, then the one and the two, killing two models
If the target player allocates, he'll apply the two, then the three, killing one model. The one then gets applied to a fresh model, leaving it with two wounds.
Or, if applied in order, I might have rolled the one first, then the three, then the two. That would kill one model and leave another with one wound remaining.

@Nij, hmm, that's more about making saves and single-wound models. The answer does actually work out to be the same, but I wanted to get an explicit answer for variable damage and multi-wound models.

With variable damage against multi-wound models (or models with a Feel No Pain equiv.) you need to roll the damage rolls one at a time. The damage is not rolled and then assigned. The only choice you would have is if you had a weapon whose profile changed based on hit/wound roll (for example d6 instead of d3 on a 6 to wound). In this case you would make two groups of wound pools, and the firing player could decide which should be applied first, the defending player would then make the saves against these. If the defending models had differing saves (or some had FNP) the saves and damage rolls would need to be made individually.
The important thing to remember is that technically group rolling is a shortcut. Each weapon is intended to be fired individually. This is of course tedious, so where possible, when it doesn't actually matter, we group rolls together.

OK, that makes sense. Though, to clarify, those three failed saves could all come from one weapon (a Grav Cannon is Heavy 4). Would it be more correct to say that each shot must be fired individually?

If you read the Fast Dice Rolling sidebar in the core rules primer, the rules are designed that you make one hit at a time, but there are situations where you can save time by making multiple rolls at once. With a Grav Cannon, I'd certainly roll the 4 hit/wound rolls at the same time. The main time you'd need to fire each shot individually is if you were shooting at a unit with mixed toughness, since the number needed to wound could change as models die.


text:
Deck Size Problems in Deckbuilding
Question: What kind of mechanic would allow players to remove cards from their constructed decks in my game?
Theory: I'm making a deckbuilding game!  So, players start with a number of cards which aren't too powerful, but are necessary in the early game.  They will invariably collect cards early on that are bad in the mid-late game portions of play.  To increase the draw probability of good cards, you will want to prune your older bad cards.  So, I need a mechanic to remove cards from play so that they are no longer in your deck.
World Building: The game has a theme of trying to get elected to an alien senate.  You and your opponents are all candidates vying for power, and the cards you play are campaign staff who have different abilities.  The hiring row contains new staff that you may purchase to aid your campaign.
Gameplay:  At the start of the round, all players select 1 card from their hand to place face down.  All cards are revealed, and effects resolve based on priority markings on the cards.  Then, players take turns doing resource management (purchasing, etc.).  Players then discard their hands, draw 3 cards (shuffling their discard pile into their deck as needed), and the round ends.
Attempted Mechanics: One early mechanic was a card cycle whose effects are to remove other cards from your deck.  This can be a bit too slow, doesn't interact well with other mechanics, and is a little too similar to another game I've played before.
A mechanic that I like is for each card to have a "severance cost" at the bottom.  The problem is, I can't figure out when this would be activated.  Paying the cost as replacement of the effect meant having to use a marker to indicate your intention, because players were accusing each other of changing their mind after cards are revealed for the round.  But if the marker is visible while people are selecting their cards, it gives away too much information to the other players.  It was difficult for players to use the marker discretely.
I decided that maybe the firing cost could be paid once per turn during the resource management step.  But then there was the issue of "Can you only fire a card you played, one in your hand, or one in your discard pile?"  Each of these led to problems, especially when cards were fired from the discard pile.
What would be a possible way for cards to be removed from the deck?

Inspired by Baseball Highlights 2045, perhaps the game is broken into mini-games. Each representing a state/region/planet/etc. that you're trying to win over in the political race. At the end of each mini-campaign, a winner is declared for that region, and the person with a certain number of won regions is declared the winner of the overall election at the end of the game. In between each regional campaign players would have the opportunity to hire/fire staff to tune their deck for the next round.
Simply put, break the game into rounds and designate adding/removing cards from the deck to happen in between these rounds. This way the game play within the rounds will not be slowed down or made more confusing.

This sounds like a really good idea! It's super flavorful, and would be functional. I'll get my beta testers to try it!

The best way is obviously subjective so I'll throw out some ideas for Severance. Here's two quick ideas to make Severance possibly work during the initial reveal:
A): When you reveal your card, orientation matters. Straight-up means play as normal, sideways means severance. This is a simple way to do it but opens up the door to misplays of "Oh, meant to fire this guy but placed him straight" or "someone slow-rolled his flip to get extra information" and what not but has the upshot of no additional pieces to keep track of.
B): Have two additional meta cards, one that says "Keep", the other "Fire" (similar to the voting tokens used by The Resistance). You would play one of these face-down along side your employee and reclaim it at round's end. This has the benefits of no physical ambiguity like option A but does require another set of components for everyone and adds another step when you intend to keep your deck intact most of the time. If you intend pruning to be an integral part of the game, maybe not the worst option.
If you don't mind having Severance happen at a later phase, this opens a few paths. Firstly, you could have the Severance effect be defined by the staff themselves. This allows them to trash additional stuff in different zones. E.g.

Mook A has "Do thing_1. Severance {cost}"
Thug B has "Do thing_2. Severance {cost} and trash a card in hand"
Intern C has "Do thing_3. Severance {cost} and trash a card in your discard pile"
Fundraiser D has "Do thing_4. Severance {cost} and trash a card in your discard pile"

Alternatively, there's also the option of having Severance be a static ability, (e.g. only trash current played card), which allows certain staffers to have abilities that modify it. E.g.

CEO E has "Do thing_5. You may trash something from your hand/discard pile instead of CEO when severing it. Severance{cost}"

Just some thoughts

I tried orientation, but that did lead to ambiguous situations about how a card was flipped or positioned.  I like the meta card idea.  I'd been toying with a token, but a card makes more sense.  It still has the problem of adding to the complexity of pieces, because there are other pieces involved for a different part.  The other things you mentioned are pretty similar to what I was thinking about in my post, but written more clearly.

"There's also the option of having Severance be a static ability, (e.g. only trash current played card), which allows certain staffers to have abilities that modify it." This. 1000x this.
You might be able to play a Bossy Manager, who can convince one of your current hand to resign. Or you might play an HR Advisor who can sever one of your discard pile. Or an HR Manager (or even HR Director) that are more expensive to buy but have more powerful abilities. Maybe the HR bods can have two abilities: either hire new staff for less cost OR sever existing staff.

From the many different deck building games that I have played I have found that the best mechanic for removing cards from the deck is indeed a card that removes another card from your deck. I find this precisely because it is a slower method that makes your decisions for what cards to acquire more important.
When I am playing a deck building game I look at cards from two perspectives when deciding what action to take on them. First is how useful will that card be in my deck and second is how useful will it be in someone else's deck. This is important because it may lead me to making a decision on a card that may not be ideal for me but will be very useful to someone else.
If you have easy access to card removal from your deck you can get players making decisions based on card denial to other players rather than what helps their deck to be better. While having limited access to card removal causes players to be more strategic about their decisions which can make for a better game.
Personally I enjoy games where card removal is harder because it adds an element to managing deck size and you will find that players can be rewarded for not making purchases at times in order to maximize the chances of getting better cards out when needed.

Additional options might be to not have a specific "this card is removed from the deck" mechanic, but using the card itself as a cost when playing or resolving something.
For example, making end-game cards require you to trash some existing cards? Perhaps your late-game campaign staff is already a senator who needs their own interns, or something? That makes you think about when you want to buy that senator, because you need crap in your hand to make it worthwhile.
Alternatively, somewhat like a above, you can have (some) cards be amplified when trashed, like having a card that says "Gain 2 {resource}, or 4 {resource} if you trash this card."
You can also use that as fuel for another card-discard; so "Gain 2 {resource}, or 3 {resource} if you trash a different card from your hand."
That mechanic is not as generic, but in return does allow more flexibility and decisions. The option of "trash a card" can be a bit lame and game-y, but the option of the campaign manager throwing an intern under the bus for a quick boost in popularity might fit the theme really well. Plus it means that "how to get rid of cards" becomes part of the puzzle, where you might need to decide between trashing a good card for a big boost, or a crappy card without getting anything back.

Adding to the amplify idea, you can add card types/names to the trash condition to further open the design space. So Campaign Manager could have "Gain {resource}, gain {more resource} if you trash an intern card". Or Publicist: "Gain {resource} if you trash a card, or gain {more resource} if you trash a money card instead".

You can have different zones that a card can be played in, for instance "Home", "Office", "Field". Cards can have different effects depending on which zone they're played in, and for some of them, playing them in a particular zone means that you're getting rid of them. But which zone means that is different for different zones, so knowing what zone someone is playing in doesn't tell you what they're doing with the card. This does mean that cards wouldn't be played simultaneously, though.

While a zoning concept does sound interesting, I think it would lead to a bit of mechanic stuffing.  Multiple zones would mean writing different effects for each zone instead of one clean effect per card.  Then it would mean cards are persistent (whereas I want them to be discarded after use) and need a way to be dealt with by the opponent.  This could also take away the simultaneous reveal aspect.  While it does have a huge flavor value for my game, I don't think it fits mechanically.

You could just add a minor phase between everyone placing their cards and revealing them. Everyone has a card down, players planning on using their card's costed ability pay the cost (or people who want to taunt other players pretend to, this is only allowed if the card they play doesn't actually have a cost), everyone reveals their card.
This still lets players jump in on paying a cost if they weren't originally planning to, but they may be doing so to no real end (reacting to actions that might not actually affect them), adding a bit of a gamble to the decision.


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Am I understanding Ulalek, Fused Atrocity?
Ulalek, Fused Atrocity says:

Whenever you cast an Eldrazi spell, you may pay {C}{C}. If you do,
copy all spells you control, then copy all other activated and
triggered abilities you control. You may choose new targets for the
copies. (Mana abilities can’t be copied.)

If it triggers, and I copy the trigger with something like Illusionist's Bracers, then the resolution of the copied trigger should itself create a copy of the original trigger.
Does this mean that I can continue to chain triggers and copied triggers for as many times as I can afford to pay {C}{C}?

Illusionists Bracers copies activated abilities, not triggered abilities. I'd suggest using Strionic Resonator as an example instead.

@murgatroid99 Echoes of Eternity is probably the best for a drazi deck, followed by Roaming Throne

The point was not to suggest a card that was strategically valuable for this deck, just a card that was an example of an effect that copies triggered abilities.

Yes, if you can get two copies of Ulalek's trigger on the stack at once, you can chain it together to copy each other spell and ability on the stack as many times as you can pay {C}{C}.
The key is that when the copy of Ulalek's trigger that's on top of the stack resolves, the other copy of the ability is "another triggered ability", so it will be copied along with the other spells and abilities. Then that creates another situation where there are two copies of Ulalek's trigger on the stack, so that creates a loop.


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Magic the Gathering - if a madness card gets discarded and you dont want to use madness does it still get exiled
If a madness card gets discarded and you dont want to use madness does it still get exiled?

It will get exiled, but then also go to the graveyard after that.

702.34. Madness

702.34a Madness is a keyword that represents two abilities. The first is a static ability that functions while the card with madness is in a player’s hand. The second is a triggered ability that functions when the first ability is applied. “Madness [cost]” means “If a player would discard this card, that player discards it, but exiles it instead of putting it into their graveyard” and “When this card is exiled this way, its owner may cast it by paying [cost] rather than paying its mana cost. If that player doesn’t, they put this card into their graveyard.”

The first ability creates a replacement effect that causes the card to be exiled, and this is not optional. The card will get exiled, which will trigger the second ability. But the second ability states that if the player does not cast the card, it goes to the graveyard.


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Understanding "Events"
I just bought the "Dominion Empires" expansion (German edition) and have a question about how events work.
Is my understanding correct, that the randomly selected events lie on the table openly, available to every player in each turn to be bought (and thus triggered) and since they are not taken, remain available for the next player?
Also, since they are not consumed or taken when bought/triggered, if I have played a card with "+1 buy", would I be able to buy/trigger the same event twice (using both of my buys), provided I have sufficient funds?

Your understanding is all correct.
While Events are printed on cards in a landscape shape; the event itself is not a physical thing like a card, but rather an task or action that you get to perform. Each time you buy an event you use up 1 of your buys (and however much money it cost). So if you have enough buys an money, you can buy an event repeatedly.*
From the Empires Rulebook:

Events are not Kingdom cards. In a player’s Buy phase, when a player can buy a card, they can buy
  an Event instead. Buying an Event means paying the cost indicated on the Event and then doing the
  effect of the Event. The Event just stays on the table, the player does not take it; there is no way for
  players to gain one or end up with one in their decks. Buying an Event uses up a Buy; normally a
  player can either buy a card, or buy an Event. A player with two Buys, such as after playing Villa,
  could buy two cards, or buy two Events, or buy a card and an Event (in either order). The same Event
  can be bought multiple times in a turn if the player has the Buys and available to do it.

*Note that certain events from the Adventures expansion specify "once per turn" or even "once per game". These are an exception to the usual rule of being able to buy one repeatedly.


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Question about Warrior mechanics
The instructions for the warrior state:

For each Traveller you have in play (including this) each other player
  discards the top card of his deck and trashes it if it costs $3 or $4.

So let's assume I have played some card that gives me +2 actions and I also have two warriors which I play for those two actions.
Does the attack on the first warrior take the second warrior into account (i.e. there are two travellers in play on both attacks, forcing my opponents to discard (and potentially trash) 4 cards)?
Or does the first attack only have the one warrior in play and only the second attack counts both warriors, forcing my opponents to discard 3 cards (1 + 2)?

Cards are always played and resolved one at a time, so your opponents will discard (and potentially trash) a total of 3 cards.
The specific sequence of events:

Play a Village

Draw 1 card
Add 2 to the number of actions you can play this turn

Play a Warrior

There is 1 Traveller in play (the one you just played), so each other player discard the top card of their deck and trashes it if it costs $3 or $4.

Play another Warrior

There are 2 Travellers in play, so each other player does this twice: discards the top card of their deck and trashes it if it costs $3 or $4.

The first Warrior will be completely done with everything it does (except being exchanged when discarded) before anything in the game knows you are going to play a second Warrior.


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Rule clarification about debt mechanics
I just bought the "Dominion Empires" expansion (German edition) and have a question about the debt mechanics.
According to the rules, when I buy a card with a certain debt value, I need to take the corresponding number of debt markers. The rules then state, that I can repay my debts at any time, including "right away".
How do I repay my debts "right away" after taking the debt markers? Since I had to take the debt markers as part of my buying phase, I can no longer play cards from my hand.
So as far as I understand the repayment of debts "right away" would need to be done with money cards I already played but which I did not use to buy something (so to say the "change left over" from my buy).
Is that assumption correct?

It is a common mistake to think of treasure as cards you play in order to buy something. Instead, it is important to remember that playing a Treasure card is almost just like playing an Action card that produces coin when played (such as Market or Legionary). Playing a Silver simply adds $2 to your pool of coins you can spend this turn, just like playing a Market adds $1.
So at the start of your buy phase, you will play all the Treasure cards you want to play this turn (which more often than not is just all of the Treasure cards in your hand). Then you will buy the card or cards that you want, and if you have leftover coin after doing so, you can use it to pay off debt.
This has the practical effect of being able to spend $4 to buy an Engineer just as if it cost $4 instead of 4 debt; but the actual steps you are taking is to first buy Engineer for $0, taking 4 debt, and then spending $4 to pay off that 4 debt.

You are correct, let say you want to buy Engineer (cost 4 debt) but only have a gold in your hand.  At the beginning of your buy phase you would play your gold for 3 coins and then buy Engineer taking on 4 debt at this point you could pay off 3 of that debt leaving you with 1 debt to pay next round.


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Can I look at my deck before playing the Zombie Mason
The text on the zombie mason says:

Trash the top card of your deck. You may gain a card costing up to $1
  more than it.

Is this a "blind play", i.e. do I make my decision to play the zombie mason without knowing what the top card in my deck will be (potentially trashing a really valuable card like a province)? Or can I look at the top card and then decide if I want to trash it or not (basically deciding if I want to play the zombie mason or not)?
From normal rules, I would expect that it is a blind play, as typically we are not allowed to look at cards in our deck, unless instructed to do so and the zombie mason does not give this instruction.
However, if it is a "blind play", it seems far too risky to ever actually use it (or at least not in later stages of play where valuable cards are in the deck).

It is indeed a blind play, you cannot look at the top of your deck before choosing what to play with Necromancer (or however else you came to play the Zombie Mason). However, unless a pile has been depleted or you have 'unique' cards in your deck (Knights, Castles, cards from Black Market, etc.) you can always choose to replace the trashed card with an identical copy from the supply. It's not a good outcome of the play, but you don't loose a card in that case.
At the start of the game, the possibility to get rid of a Copper or change an Estate into a Silver or other 3-cost card is really good. If you trash an Action card, no problem, another potential card to play with Necromancer.
Later in the game you might be wanting to play either other Action cards trashed, or another Zombie. But if you are ahead in scoring, accidentally trashing a Province and replacing it with another isn't a bad outcome anyway.


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Dominion: How exactly do cards "enter play"
Today we played our second round of Dominion: Nocturne. Quite a few cards (among others: Raider, Magic Lamp) refer to cards being "in play". Even though we are seasoned players of other dominion extensions, we have so far never seen the need to follow the rules too closely with regard to distinguishing between cards "on the hand", "in play" etc, mainly it was "play actions from your hand" and "buy cards with the amount of money and buys at your disposal".
However, today we suddenly realised it became important to do this more conscientously to be able to use the new Nocturne cards.
My understanding of the rules is as follows (though not everyone in our round agreed even on that):

at the start of your turn, the cards in your hand are obviously "on your hand"
at the start of your turn, any duration cards from previous turns are already "in play"
as you play actions, the go from being "on your hand" to being "in play"
at any time before your buying phase, you can lay down money cards, therefore also moving them from "on the hand" to "in play", by doing so, you increase the amount of money available in your buying phase (increased by any text on action cards you may have played)

Is that understanding correct?
Also, it is my understanding that any action card that refers to "cards in play" only takes into account those cards you already moved from "your hand" to "in play", meaning that it matters whether you place your money before or after playing an action card and that there is no fixed time when you play your money (i.e. before or after playing an action). Is that also correct?
Furthermore, as the night cards are played after the buying phase, all actions that were played during your turn and any money played before your buying phase is considered to be "in play". Is that also correct?
After the night phase, any card "in play" goes to the discard pile (except for duration cards that will be kept for the next turn).
Any card not having been played, remains "on the hand" and goes directly to the discard pile, without ever entering play.
The above summarises my understanding of the rules. Is that correct or are there gaps in my understanding?
However, the main point of contention/confusion is if there is any way of bringing "point and/or curse cards" into play, or do they always stay "on your hand" and go straight to the discard pile? This is relevant as it may help to attain the exact number of cards in play for "Magic Lamp".

Quotes from the Q in italics and marked with >>, other quotes are from the rules.

>> as you play actions, the go from being "on your hand" to being "in play"

Yes. Second edition rules, p. 4:

Playing an Action card has three steps: announcing it; moving it to the "in
play" area - the table space in front of you; and following the instructions on it

Same for Treasures, see below.

>>  at any time before your buying phase, you can lay down money cards, therefore also moving them from "on the hand" to "in play",

Playing Treasures happens during the Buy phase (but has to be done before actually buying something). You can't do it in the middle of the Action phase, so definitely not "at any time". This matters very much for the Actions that say "discard your hand". p. 5:

Buy Phase: First you can play any number of Treasure cards from your hand, in any order. [...] You play one by moving it to the "in play" area;

There's nothing in the rules about playing Treasures during the Action phase.

>>  Also, it is my understanding that any action card that refers to "cards in play" only takes into account those cards you already moved from "your hand" to "in play"

Yes, "in play" is explicitly stated as a distinct "area" for the cards to exist. It also matters if you have to reshuffle mid-turn: discarded cards get reshuffled, cards "in play" do not.
Note that the Action or Night card you just played is also "in-play" when it is processed. This follows from the sequence described above, and is reinforced by the FAQ for e.g. Magic Lamp and Raider (also at the back of the Nocturne rules).

>>  meaning that it matters whether you place your money before or after playing an action card and that there is no fixed time when you play your money (i.e. before or after playing an action). Is that also correct?

No, see above.

>> Furthermore, as the night cards are played after the buying phase, all actions that were played during your turn and any money played before your buying phase is considered to be "in play". Is that also correct?

Yes, except that the money is played during your buy phase. The Night step happens before Clean-up, which is where the "in play" cards are put to the discard pile. Nocturne rules:

Nocturne adds Night cards and the Night phase. In games using Night cards, the Night phase happens after the Buy phase - it goes, Action, Buy, Night, Clean-up.

>>  After the night phase, any card "in play" goes to the discard pile (except for duration cards that will be kept for the next turn).
>>  Any card not having been played, remains "on the hand" and goes directly to the discard pile, without ever entering play.

Yes. The rules don't say anything about the cards going "in-play" in between. (And why would they, they were never played.) Second ed. rules, p. 5:

Clean-up Phase: Take all of the cards you have in play (both Actions and Treasures), and any remaining cards in
your hand, and put them all into your discard pile.

Nocturne, p. 4:

Nocturne has Duration cards, [...] Duration cards are not discarded in Clean-up if they have something left to do; they stay in play until the Clean-up of the last turn that they do something.

>> However, the main point of contention/confusion is if there is any way of bringing "point and/or curse cards" into play, or do they always stay "on your hand" and go straight to the discard pile?

Unless there's a rule or a card that allows playing them, then no, you can't play them. The easiest way to get a Victory card "in-play" is probably the dual Victory/Action and Victory/Treasure cards from Intrigue (e.g. Harem), but that of course only works
because they're also Actions or Treasure. (I can't think of any ways to play them purely through being Victory cards, but that doesn't prove there isn't one.)

About the closest I can think of getting a pure Victory card into play is when you buy the Inheritance Project (from Renaissance), Estates become Victory-Action cards so that you can play them.

@ConMan, yes, that's a good one. Though strictly speaking, the FAQ says they too turn into Victory-Action cards (during your turns) :)

Yes, which is why it's still not quite the same. Although if you Inherit a Duration card, the rules say that the Estates stay in play across turns so technically it will revert to being a pure Victory card but still be in play. So while you don't play it as a pure Victory card, it is in play as one at some point.

@ConMan, hah, ok, I guess I'll have to accept that argument :)


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Does Leonin Arbiter affect Karn, The Great Creator from choosing a card outside of the game?
You have Leonin Arbiter with the static effect that players cannot search their libraries unless they pay 2 to ignore it. But Karn, The Great Creator
ability for -2 is "You may choose". Does sideboard count as library? Then if so, I assume then Leoning Arbiter affects this?

No, Leonin Arbiter has no effect on Karn's ability. The library is a specific zone in the game; it is where you put the deck to start the game, and it is where you draw cards from. The sideboard is a completely separate thing outside of the game; it is normally used for switching cards into and out of your deck between games in a match, and only specific effects like on Karn can access it during a game.