text:
How often do top duplicate Bridge players repeat the same game?
For the purposes of this question, we neglect plays that don't matter (i.e. plays that don't affect how the hand plays out).
As I understand duplicate bridge, two teams play the same hand from different sides - so one pair plays E/W, the other plays N/S, for the exact same hand. The format is naturally balanced to wash out luck, and for one team to win the match, they need to win one hand by more than their team on the other table loses it by.
It also opens up the possibility for effectively the same contract and result to be repeated on both tables because all players involved agree that there is a "best play". How often does this happen?

Let's check.
Here are the hand records and session results for the 44th World Team Championships' Bermuda Bowl Final between Poland and Netherlands. Given are the session number and number of hands scored at 0 Imps, ±1 Imps, and Other score

Session #
0 Imps
±1 Imps
Other

1
9
0
7

2
3
3
10

3
5
1
10

4
6
1
9

5
6
3
7

6
5
3
8

-----------
--------
---------
--------

Total
34
11
51

Of 96 hands played in this final, about 1/3 (34 boards) were scored at 0 IMPS and 1/9 (11 boards) scored at ±1 Imps (usually an overtrick, but not always). A more detailed analysis reveals that 3 of the 1 IMP results were not an overtrick:

Session 3 Bd 11: 3C by N - 2 vs 1 NT by E +1;
Session 4 Bd 17: 1 NT by E +1 vs 3 S by E just in; and
Session 6 Bd 24: 3 S by W just in vs 2 NT by N -2.

In summary only I also checked out the 96 board Semifinal between USA 1 and England. Here (by my quick count) there were 37 0-IMP boards and 12 1-IMP boards; results quite similar to above.
These results are consistent with my personal recollection, from 40 years as a competitive bridge player, that somewhere around 1/3 of hands played are uneventful: barring a significant error by one side or the other.

For what it's worth, 2 of the 0 IMP boards had a 10 point difference.  These were Board 21 in Segment 2 and Board 12 in Segment 3.  I don't think any of the boards with the same score were in different contracts, but I didn't check very carefully.

@AlexanderWoo: Thank you for checking that. I expected that to be uncommon; it's reassuring to see that confirmed. The other factor of possible interest, which I didn't check, is to see if any of the swings were the consequence of playing the same contract in different directions. Again, I don't expect it to have much effect on the stats.

Ignore "plays that don't matter".  That's a very hard statement to define, and could massively affect your answer.
The other answers are talking about "same contract leading to same result".  Which is one answer and a very useful one.  But it hides the hands where, for instance:

one declarer got a friendly lead and took the obvious tricks, but the other declarer got a bad lead and hand to execute the pentagonal squeeze to achieve the same result;
the defenders, on the run of the diamonds, pitched the relevant card to allow pickup of the rest of the tricks, where at the other table the defenders played perfectly but declarer guessed the end position right anyway; or even where
declarer played it like a fish, but the opponent's revoke, and subsequent one-trick penalty, brought them back to average.

But not only that.  As I have made clear in other answers, in my most common partnership, I play an anti-field system (K/S, with 12-14 NT).  That means that whether or not we end up in the same contract (from the same side, even), the auctions on all hands where we open with 12-17 HCP and balanced distribution will almost certainly be different than at the other table(s).  And that means that the information available to the opening leader will be different.  And that means, often, that the play of the hand will be different.  Even if it results in the same score, does that mean that "the play didn't matter"?
And the pair that plays Precision.  Or opens weak 2s on J-sixth.  Or plays Suction over NT vs DONT vs Meckwell vs Landy vs Natural.  Even the pair that plays coded 10s and 9s, or odd-even discards, vs the "standard" players.
Yes, there are hands where "all roads lead to 4♠ and there are three unavoidable losers".  From my experience, they come up maybe 4-5 hands in a 27-board set.  And even then, only 1-2 actually are flat-across-the-room, 0-1 if there are more than say 6 tables in play.
One of the things that make expert players expert is that they can win a match 25 IMPs-3 with the same hands that I play to a 5-3 "winning tie" (and one of those swings was "1♣-1♥; 2♥ vs 1NT-p" and the other was "1♣-1♥; 1NT-2♥ vs 1NT-2♦; 2♥").
Another thing (very obscure) to think about is the difference between matchpoints (frequency of wins) and IMP (size of wins) play.  There are "boring" hands at both styles, but in a 60-board IMP match, they might not think quite as hard about the overtrick in 3♥ (where it might cost 1 IMP.  A "well-played" scoreline in world-class competition is "2 IMPs a board", so say 75-55.  Fatigue over that 1 IMP might cost 10 down the line) as they would in a 101-table matchpoint game (where the difference could be between 65% and 35%, and that's the same as the next hand's difference between -100 and +420).  Or they may not compete as hard, knowing that it's wrong 15% of the time, but when it's wrong, it's -1100 and 14 IMPs (versus "a bottom, but the 50% of the time it's right, we gain half-a-board).
So the number of boards where "the play doesn't matter" could be very different on Saturday (the two session Open Pairs) and Sunday (in the Swiss), even if they were the exact same boards (played by two different sets of people, of course).

It seems to me this is a well written right answer - to some other question tan the one actually posted. I'm in agreement with everything you've said - and on a good day might write it up almost as well - but fail to see how it addresses the question asked.

Perhaps true.  But the whole point is "if the plays don't matter".  And that isn't defined, except "plays that don't affect how the hands play out".  And if that means "ends up with the same score", fine.  If that means "playing the 6 instead of the 4 for 'it's an x' reasons", then my answer is "it so rarely doesn't make a difference to the play (not the score) that we actively discourage using 'x's. Which, of course, we do. And there, the answer to the question "how often is the contract and result the same because there's an agreed 'best play'?" is "almost never, because."

I believ0e you're missing the forest for the trees. It is the semantics of a signal that matters, not its syntax (ie choice of card according to partnership agreements). When I was learning the top players I hung out with would repeatedly note: "There's one thing Partner needs to know. Figure out what that is; and inform him as best you can." The message to be sent only rarely depends on the carding agreements.

Anecdata from a not top player:
I played matchpoint pairs in a 4 table game (online) on Wednesday.  Out of 21 hands, our results matched (same contract and same number of tricks, but not necessarily the same declarer - note same score with different contracts are being counted as different) with
All 3 other tables once
2 other tables twice
1 other table 6 times
No other tables 12 times
That comes out to 13 identical results out of 63 possibilities, a little more than 20%.
Every pair played some version of standard American (I consider 2/1 a version of standard American), but unusually for a game in the US, 3 out of 8 pairs were playing 12-14 1NT openings.  Not all the players who were in the game are good, and I would expect more advanced players to match more often.
Two weeks earlier:
10 tables, so 9 comparisons; on 20 hands we shared results with:
6 tables once
5 tables once
3 tables twice
2 tables 4 times
1 table 3 times
0 tables 9 times
Out of 180 possible comparisons, 28 matches, a bit over 15%.

You’re describing one kind of duplicate - it actually is the less common kind. The more common is matchpoint pairs, and in that format you have maybe a dozen or more sets of four people play the same hand.
In pairs, you probably have an identical game played on most boards between at least two of the pairs- but also never few boards with entirely identical results across all pairs (but not zero, you’ll find boards like that where it’s just obvious as you say, even two different systems will find the same obvious 4 spades). Some boards will be more similar than others - but plenty of them will be completely identical.
I’m not sure top players actually will play identical boards more often than experienced but not expert players. Top players may introduce more differences in an attempt to find edge cases, or just have different styles - one pair playing precision and one pair playing a more standard system.


text:
Monopoly: If I had all properties of a colour but sold one of them, will I retain houses on the other properties of that colour?
Let's say I have every property of a colour, and sold one of them to another player. Since I won't have all properties of that colour anymore, will I lose all the houses I built on the other properties of that colour (which I haven't sold). Or will I still retain them?

This cannot happen as stated. You have to sell off improvements before you can sell the property. From the rules of Monopoly:

Selling Property

Unimproved properties, railroads and utilities may be sold to any player as a private transaction for any amount the owner can get. However, properties can not be sold to another player if buildings are standing on any properties of that color-group. The buildings must be sold back to the Bank before the owner can sell any property of that color-group.

The complementary rule is that you must have a complete set to develop any property in that set.

source: Stack Exchange

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sort: votes


text:
How does Death's Shadow interact with Trample?
Inspired by Does Death's Shadow grow when blocking a creature while the player is taking damage?
Let's say I control a Phyrexian Dreadnought - a 12/12 Trampler. My opponent is on 12 life and has a Death's Shadow, currently 1/1.
I attack, opponent blocks. Trample says I need to assign "lethal damage" to the blocker, presumably 1 damage in this case, and then any excess damage goes to the player. But if I assign 1 damage to the Death's Shadow and 11 damage to the player, then the Death's Shadow becomes a 12/12 with 1 damage marked on it, which is not lethal. In fact, some math shows that I need to assign at least seven damage to the Death's Shadow to actually kill it, in which case opponent only takes 5 trample damage.
Can I trample over for 11, or only for 5?

You are conflating "assigning lethal damage" and "actually killing the DS". Just because the minimum required assigned damage (i.e. 1) doesn't end up killing the DS doesn't mean it was an illegal damage assignment.

In the Combat Damage step, you must assign lethal damage to the Death's Shadow - this is unambiguously 1 at this stage because the Shadow has 1 toughness and no damage marked on it. You can then assign the rest of the damage to the player if you wish; from 702.19b (Trample):

Once all those blocking creatures are assigned lethal damage, any excess damage is assigned as its controller chooses among those blocking creatures and the player or planeswalker the creature is attacking.

There is now nothing in either CR 510 (Combat Damage Step) or CR 702 which specifies that the damage assignment must/can be changed if the "required" lethal damage for a creature changes so combat damage is dealt as assigned. (CR 702.19d covers the case where a blocking creature is removed from combat entirely, but that's not what's happening here).
Note that the converse can apply as well: for example, if you have Torbran, Thane of Red Fell

If a red source you control would deal damage to an opponent or a permanent an opponent controls, it deals that much damage plus 2 instead.

in play and are attacking with a red creature with trample, you must still assign 3 damage to a 3/3 blocker even though 1 damage would be sufficient to make it die.

It might be worth clarifying that the common understanding of “creatures simultaneously deal damage equal to their power” occurs in two distinct steps, first assignment, then dealing the assigned damage, which would demystify why you can mark 1 damage even though it won't be lethal. I envision that being similar to what I did here, albeit at whatever level of detail you're comfortable with, but it's worth just mentioning there's two entirely separate steps.

Given that question is linked from here, I was sort of hoping people would read that first; there seems little point me repeating what are the answers already there... maybe I'll link more directly from this answer as well.

Damage reduction, protection, and indestructible are also cases where trample only needs to assign "lethal damage" even though it won't actually be lethal.

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text:
Import cards without knowing set in mtggoldfish
I want to use the "my price" feature in mtggoldfish, so I need to import my collection. I have my collection in a spreadsheed, but I don't have the set names for each card, and for the purposes of "my price" feature I shouldn't really need them so I don't want to go through and do all the data entry to list them. Is there any way to import as "unknown set" or "set not listed" or anything like that?

Have you considered contacting the site and seeing if they can provide you with the information you need? https://www.mtggoldfish.com/contact

Yes, I also contacted them. If they get back to me, I'll add the answer here. But maybe someone already knows the answers and sees this before the site admins do.


text:
Why don't the meanings of specific bids need to be considered when giving advice?
Inspired by many bridge questions on this site, e.g. this or this.
As I understand bridge bidding systems, they are very detailed, for example in a comment to one of my questions David Siegel wrote:

In the variant of SA that I play, an opening bid of 2 C says "I have at least 20 points, or at least 8 playing tricks". A 2-club response to partner's 1C opening says "I have at least 5 clubs and more than 10 points, and no 5-car H or S suit" a 2 C overcall over opponent's 1S opening says 'I have at least 10 points and at least a 5-card club suit"

Since the bid conveys serious information, why don't the answers to most bridge questions begin with "that depends on what your bidding system is"? For example, for the first linked question, it seems reasonable (maybe even crucial) to ask "what does South's 1H bid mean?", and without that information it seems pointless to even try to answer the question.

Short answer: Almost everyone other than top experts, absolute beginners, Poles, Chinese, and British play variants of the same bidding system.

There's a very old quote by one of my teachers: "Don't let mycroft near the novices."  And it's true.  Because my answer to most questions about bidding is "it depends"(*).
It depends on the system you are playing.
It depends on what conventions you have available, and what conventions you don't use, and what room you have to replace a natural sequence with a convention.
It depends on your style for opening (especially pre-emptive openings).
It depends on your opponents, and their system and agreements - and skill level and state of the match and whether you have a history (or, indeed, a history).
But a lot of that applies to your constructive [when the opponents aren't (yet) in the auction] bidding only.  Even the "what do I do with this hand after partner's 2♥?" question - which frequently isn't a "our hand" auction - depends strongly on what you expect for partner's 2♥ opener.
When the opponents are in the auction (and not just preempting) - when it is competitive, in other words - a lot of "that depends" goes away, because the goal stops becoming "find our best contract, giving away to the defence only what information is necessary" and becomes "win the partscore" - go -100 into -110, or +110 into +100, and definitely avoid -800 (**).  And those rules are much more easily prescribed by results - there really is "one right way" to do it (or at least it's much closer).  Hence all of Tom Au's takeout double questions and "why is this 9-count worth more than this 13-count (or less than this 5-count)" - there's one right way to do it, because wrong ways can get punished more often; and good players know when to punish.
Defence is even more than bidding defined by the math.  Sure, signalling choices change the information available, as does the auction, but the "right choice" based on the information given is all down to statistics (or "only hope"s), and players good enough to play at world championship level know how to work out those statistics and only working positions.  So when someone plays "a non-standard style", and it works measurably better than the way everyone else knows is right, then either the math works out and "everyone" starts playing that way, or it doesn't work out, and people start looking for other reasons it works for "someone" and not, say, for them.
What Joe says is also correct, however, especially in North America. There's A Style (which because I'm an old C hand, I call the "One True Bidding System".  People either get it or they don't) that is so common and so universal that I can sit down with anyone, agree "2/1, with [defence to NT], [preempt style], and [keycard version]" and a) partner can play it, and b) we'll get 80+% of auctions right.  And so, unless otherwise specified, questions asked are assumed to be in that framework.  And in that framework, at least for the first round or two, there is very often "the answer" - imposed by system.
What you say in your comment to Joe's answer is also true - 12-21 (Opener's 1-of-a-suit) is a massive range (***), and there are some serious holes in a standard/ 2/1 system that need to be covered by conventions, mostly around resolving that massive range.  And others that players like to cover with conventions, even if it's not necessary.  And there are choices in what, if any, conventions to play and what holes to live with.  And there - is where, even in an assumed 2/1 base, "it depends".
So, yes, "it depends".  But frequently - especially in newspaper bridge columns and periodicals (The Bridge World excepted - it deliberately aims at experts) - unless they're trying to stump for their pet methods, there will be "the answer".  In fact, the hands are chosen partly so there is "the answer", most of the time - with maybe one outlier that shows potential problems or potential choices.
And you can see from the number of side paths and "mostly"s and ... even in this answer, that "it depends".  And that maybe I'm not the best person to answer this question to a new/non-bridge player...
*) new players can't use "it depends", they need "the answer".  Even if it comes along with "as you get more experienced, you will find that there is another answer that works better - or works better for you.  But for now, this."  And I'm horrible at doing that (and frequently can't think down far enough to see it), so all I do is confuse.
Note that when they get slightly more experienced than "novice", where they can see the interactions, I am considered a very strong teacher, and many come to me with these kinds of issues.  But, still, "it depends"; and what's right for me, or what's right for my partnerships, can very much not be right for the questioner.
**) Okay, at IMPs and money bridge.  Matchpoints has its own reward structure based more on frequency than size of wins and losses, and that limits the amount of the potential win or loss in a way that "real bridge" doesn't.  But most bridge writers are most often either discussing high-level events (which are more often long IMP-scored team matches) or advice for "kitchen" level players (who score rubber or Chicago - "money bridge", even if there isn't any stakes).
***) In fact, a majority of systems that aren't OTBS (or simple swaps to weak NT or the like) have an explicit goal of limiting the one-of-a-suit openers.  Whether it's Precision (10-15) or Polish Club (12-18ish) or even Strong Pass (8-12).  Even K/S (the weak NT system I play) has a goal of making at least the 1♣ and 1⋄ openers better defined, by taking out most minimum hands (either to 1NT or pass).  Of course, they all do it by making something else harder to deal with.  If that weren't the case, there would truly be OTBS.

I assume you also agree carding.  With that caveat, 80% is an underbid.

Certainly.  I thought about putting it in the answer but as it wasn't bidding, I thought it would confuse.   I explicitly said "80% of auctions" : -) Maybe I was wrong.

You're not wrong; certainly the meaning of the bids is important to the question, and can vary from partnership to partnership.
However, the far majority of people play a variety of "2 over 1" or "Standard American", both of which are very similar in how they treat many bids especially at the opening.  For most, 1H = 5 hearts and 12-18 points, give or take a little.  Thus, bridge questions that ask about things like that (like your initial question) tend to assume that people are playing some variant of the standard systems - if they are, for example, playing precision club, one hopes the question would include that information!
Further, when asking about a response to an opening bid, it matters somewhat less what the opening bid means.  Not to say it matters not at all - but it's reduced to "natural" versus "artificial", and nothing beyond; and again, one hopes that the initial question or bridge article would mention if 1H were artificial.
Ultimately, many of our questions/answers do end in "it depends" answers, of course.  That doesn't mean you can't have a useful discussion (or answer, in this case) that is grounded in strategy; perhaps "is this double for takeout" is in part dependent on agreements, but "should this double be for takeout" has a useful answer ("if you agree this is penalty, you'll not gain very much, but if you agree it's takeout, it's useful for XYZ reasons").

12-18 points? Isn't that a huge range? It's two extra Kings or an Ace + a Queen.

Sure, the initial 1H is 12-18 (and it's really more than that, 12-18 or 12-17 is just for 1H-[normal responses], it can go up to 21 really).  The responses tell partner what part of the range it is in.  If big ranges like that bother you, play precision club :)

@Allure As Joe implies, you could play a highly artificial bidding system where your first bid gives your point count within a narrow range. However, points aren't everything, or even the most important thing, so the disadvantages of that approach tend to outway the advantages. You could fill a whole bookshelf with discussions on the relative merits of artifical vs natural bidding systems though.

A full answer to any such question does indeed depend on the biding systems in use, at least those used by the partnership begin addressed, and may well be far more detailed than any answer on this site is likely to be. If you read a bridge column, particularly one aimed at intermediate players or higher, there will usually be some indication of the bidding system(s) that the players are using. Unless the point of the column is to compare systems, however, this will not be emphasized. Rather, having mentioned the assumed system once, the author will take it for a given, because the point is to compare different possible actions and sequences within a given system. Indeed many continuing professional columns simply indicate that all discussions in that column use a particular system.
It is also true that several of the systems in wide use, particularly in North America, have a similar general structure, differing only in certain specific aspects (althoguhn that difference may be vital when one of those aspects comes up)
Mycroft writes:

[a style] is so common and so universal that I can sit down with anyone, agree "2/1, with [defence to NT], [preempt style], and [keycard version]" and a) partner can play it, and b) we'll get 80+% of auctions right.

While it is true that that sort of bare-bones discussion will allow two good players who have never played with each other to do reasonably well, that is partly because there are widely known and agreed "defaults" which say things like "If your partnership hasn't agreed to play convention X, it is not in use, and the more basic convention Y is in effect". Indeed there is a whole system defined for such cases, known as "ACBL_Yellow Card" that has no options at all. The idea is that two players can say just 'yellow card' and they have agreed to several pages of conventions, and to no others.
I recall playing in a weekly individual "pro-am" match at a club long ago. In an individual one changers partners every two or three hands, and in a "pro-am" the players are divided into two general groups by ability, and each pair consists of one stronger and one weaker player. At those games three fairly basic systems were sketched on a chalk board at the front of the room, and each pair was to agree on just "System 1", "System 2",  or "System 3" when they sat down together, no other options, because there wasn't enough time for detailed discussion.
That said, when I meet a player new to me at a tournament, I prefer to have 20 minutes to half an hour to discuss the various choices of conventions we will use, and so do most other players in my experience. If I make an advance date to play with a partner new to me, I will often have several telephone calls (totaling perhaps 3 hours of discussion) and several exchanges of emails with lots of "If I bid this and you respond that, what should I do with holding ABC? What about holding XYZ?"  I find this level of preparation often leads to significantly better results than the 30-second version specifying three or four key choices.
Thus most answers here and on more advanced bridge forums either explicitly or implicitly include a certain system or range of related systems in determining what actions to consider, but except for those discussion devoted to comparing systems, the system involved is rarely more than briefly mentioned, instead it is an underlying assumption.

Also, the question asks about "the meanings of specific bids". If one is speaking strictly, there is usually no such thing as the meaning of a specific bid. What has meaning is a bidding sequence. Consider the partial auctions:

1H - 1S - 2NT - 3D (E/W silent)
3D- P - P - P
1H - 2D - P - 3D
1H - 1S - 2H - 3D (E/W silent)
P - P - 1H -P - 2C - P - 3D

the bid of 3D has a significantly different meaning in each of these 5 sequences. Normally a bid is meaningful only in terms of the entire auction up to that point, or at least the immediately proceeding two or three calls by the partnership.
(The following is based on he versions of Standard American I tend to play. In the first auction 3D might be showing a diamond stopper, or agreeing a heart contract, depending on the partnership agreement. In the second it shows a weak 7-card diamond suit. In the third it shows diamond support, and at least hints at a 5D contract. In the fourth 3D firmly denies a heart fit. This may be a misfit hand, or it may work at 3NT if opener has a club stopper or two. Or if the pair is playing "new minor forcing" it may just show extra strength and a desire to hear more from partner, and say nothing about diamonds. The fifth is probably a Reverse Drury response showing a full opening bid with extra values and a diamond suit.)


text:
Who decides the trigger if control of the permanent changes before the trigger resolves?
For example, suppose I have an Aether Vial. It's my upkeep and the Vial triggers. In response to the trigger, opponent plays Archmage's Charm, choosing the third mode to gain control of my Aether Vial. After the Charm resolves, who decides if the Vial gets a charge counter?
Relevant text of Aether Vial:

At the beginning of your upkeep, you may put a charge counter on Aether Vial.

Could you rephrase at least the title there? "Who decides the trigger if control of the permanent changes before the trigger resolves?" means what in English, or any other language?

@RobbieGoodwin I can understand the title (although it admittedly uses a lot of Magic jargon). Feel free to edit the title to something else if you like.

The player who controlled the permanent from which the ability triggered is that ability's controller on the stack. That would be you.

109.5. The words “you” and “your” on an object refer to the object’s controller, its would-be controller (if a player is attempting to play, cast, or activate it), or its owner (if it has no controller). For a static ability, this is the current controller of the object it’s on. For an activated ability, this is the player who activated the ability. For a triggered ability, this is the controller of the object when the ability triggered, unless it’s a delayed triggered ability. To determine the controller of a delayed triggered ability, see rules 603.7d–f.

This is consistent with the general rules for abilities:

113.7a Once activated or triggered, an ability exists on the stack independently of its source. Destruction or removal of the source after that time won’t affect the ability. [..]

If a change of control after activation/triggering mattered, then destruction of the source of the ability would also change its controller, presumably to no controller, and "you" in the ability's text would not refer to anyone.

This has all the correct info, though you may want to highlight the part relevant to triggered abilities instead of activated abilities, since the ability in question is a triggered ability: "At the beginning of your upkeep, you may put a charge counter on Aether Vial."


text:
Is Boseiju, who Endures' channel ability blocked by protection from green?
Card in question: Boseiju, who Endures
I'd normally expect Boseiju's channel ability to be colorless because it's a land with no color identity. In the same vein, to my understanding, Forests are not actually green even though they tap for green mana. On the other hand, Boseiju is colored green. Is it actually green? Is it affected by protection and other green-only effects?

Forests are also 'colored' green, it's an unfortunate design choice that they color lands based on the color(s) of mana they produce, confuses a lot of players into thinking the lands have color.

Boseiju is colorless, not green.
Rule 105.2 describes how objects get their colors:

An object can be one or more of the five colors, or it can be no color at all. An object is the color or colors of the mana symbols in its mana cost, regardless of the color of its frame. An object’s color or colors may also be defined by a color indicator or a characteristic-defining ability. See rule 202.2.

Boseiju has no mana cost, color indicator, or characteristic-defining ability. The frame is purely cosmetic, and has no effect on the the in-game color.

The only existing land that is not colorless is Dryad Arbor, because it has a green color indicator.

Does this mean "Protection from colorless" will block Boseiju?

Yes.  [Adding characters to get to 15]


text:
Is it good etiquette to gg the opponent when they gg you, even if you haven't won yet?
Say you have some strong board position and are clearly winning, but you have not won yet. Opponent ggs you (i.e. uses the in-game 'good game' command). Should you gg back?
For context: you are winning, but not won yet. For example, you might have 10 power worth of attackers and opponent is on 12 life with no board and no cards in hand, but they do have Wrath of God, in their deck and if they just topdeck the wrath then they're right back in the game. They also have two draw steps to find the Wrath, since you do not presently have lethal on board.
It seems to me that most players gg the opponent right before they concede, but not always, and in the situation above they ought to not concede (unless they are on tilt, I guess).

Do people do this in chess / 9LX ?

Usually people use gg as well when they think they can't win. While your example still has a win/ turnaround condition, in an online game where people are quick to jump to a new game, there is the possibility that otherwise you would not even notice the gg since it gets lost in victory message/ restart. So a tiny bit early gg will make sure that the opponent sees it. And you can always thank them for a good game, even if it is not over yet

I think this is a question about your personality, not etiquette.

@BorisVerkhovskiy There are definitely some generally accepted standards for the use of emotes on Arena; that is pretty much the definition of "etiquette".

I often gg when I think I'm going to win. Sometimes I'm completely wrong and opponent has a wrath or somehow scrape through and turn the board around, and that's funny. On the other hand, if I see opponent has a cool combo I often let them play it out. If I've got a powerful combo it's a little disappointing when opponent concedes before I can really blow up.

@MatthewJensen gg'ing when in a winning position is generally considered bad etiquette on Arena. (No point debating this with me by the way: I don't necessarily agree with it, but it's the way it is).

@PhilipKendall I will definitely take that on board. I don’t play seriously enough to know the etiquette.

Disclaimer: Arena emotes, beyond maybe one "Hello" at the start of the match, are a touchy area all round. I'd honestly advise either just turning them off or ignoring them; nobody will criticise you for doing that.
With that out of the way, there is nothing wrong with replying "Good game" when an opponent says the same to you. If they're not immediately (as in "before taking any more game actions") conceding after their "Good game", they are breaching what etiquette does exist.
Similarly, I wouldn't worry about why they're conceding: maybe they're just grinding out their 15 daily wins and want to get to the next game as soon as possible, maybe their dinner was ready and they had to leave.


text:
In Magic, are you allowed to reveal what cards you have drafted to stop others from drafting the same colors?
For example, suppose I open a [bomb Boros mythic]. I reveal it, and say "Ok guys I'm drafting Boros" (with the implication that everyone else should avoid fighting me over those colors). Is this permissible?
If it is not permissible, am I allowed to say "Ok guys I'm drafting Boros" without revealing the card? If this is also not permissible during a draft, can I reveal my preferred colors before the draft?

To be honest that would not stop me from drafting a color and could make me prioritize that color if I was looking to draft it.

yeahI'm not so sure that's a sound strategy either. If all other players make just 1 hate pick each because of your reveal, you dont have a deck any more.

Depends on who you're drafting with. If the other players are either naturally cooperative, or are experienced enough with draft that they know it's in their best interest to be cooperative, it could be pretty effective.

In any case, there is to consider that there's only five colors, and eight players at the table. Even if you somehow attempt to share equally and fairly, someone will be losing out - and if everyone does that math, they might be inclined to deviate from the fair path. Distributing cards by color intentionally seems like it would be a kitchen table format, not something that the existing Draft framework is very suited for.

@Hackworth Hate picking is generally a bad idea though. The main reason is making your deck stronger is more important than making one of the seven opposing decks weaker. https://magic.wizards.com/en/articles/archive/beyond-basics/dont-hate-draft-2016-07-28

The MTR (Tournament Rules) indicate that you are not supposed to reveal the contents of your booster (which includes your pick); visually or otherwise. You may, however, reveal double-faced cards.

7.7 Booster Draft Procedures
(...)
Players may not reveal the front face of their card selections or the contents of their current packs to other participants in the draft and must make a reasonable effort to keep that information from the sight of other players. Players are not permitted to reveal hidden information of any kind to other participants in the draft regarding their own picks or what they want others to pick. (Exception: This does not apply to double-faced cards, both faces of which may be revealed at any time during a draft.)

The Tournament Rules can be found here: https://wpn.wizards.com/en/rules-documents
An alternative source that provides comments from/for judges is the Judge rules resources: https://blogs.magicjudges.org/rules/mtr7-7/
As for whether revealing your favorite cards before the draft is permissible: The rules don't explicitly disallow it, and of course chatting about your favorite colors for decks before a match shouldn't be a problem. If I try really hard, I can think of scenarios where this might fall into collusion or unsporting conduct territory, but you would certainly have to get there intentionally.


text:
Why doesn't Authority of the Consuls prevent the goblin token from Den of the Bugbear from attacking?
While playing on Arena, I had 3 life left and an Authority of the Consuls on the board. My opponent had a Den of the Bugbear on the board and paid the one red and 3 colorless mana so that it became a creature and attacked.
The Den of the Bugbear ability

Whenever this creature attacks, create a 1/1 red Goblin creature token that's tapped and attacking

triggered, created a goblin token. This in turn triggered my Authority of the Consuls:

Creatures your opponents control enter the battlefield tapped.

I then lost because the created Goblin token also attacked. Why was the Goblin token able to attack, when it was tapped? It was clearly affected by my Authority of the Consuls since I gained one life. I know that "comes into play attacking" is not the same as haste but as far as I know a tapped creature cannot attack.

To reword your question to fit the mechanics, "Does tapping an already attacking creature prevent its attack?"  This answer talks about tapping or untapping an attacking creature and whether it stops the attack.  https://boardgames.stackexchange.com/a/13189/14403

The Goblin token is already attacking, so it doesn't need to be able to attack, and it's already tapped, so Authority of the Consuls doesn't do anything relevant anyway.
The specific sequence of events goes like this:

The opponent activates Den of the Bugbear, making it a creature for the turn.
Combat starts, and the opponent declares Den of the Bugbear as an attacker. Den of the Bugbear is now an attacking creature. This triggers the ability that it gained when it became a creature.
The Den of the Bugbear's ability resolves, creating a Goblin token that is tapped and attacking. This Golbin token is now also an attacking creature. Authority of the Consuls also makes it enter the battlefield tapped, but it already enters tapped so that doesn't make a difference. This also triggers Authority of the Consuls' second ability (for completeness).
Authority of the Consuls' second ability resolves, and you gain 1 life.
The rest of combat plays out as usual, with Den of the Bugbear and the Goblin token as the attacking creatures.

There is a difference between a creature actually attacking, and being declared attacking. The same is also true with creatures actually blocking, and being declared blocking. This arises from the fact that while not explicitly a status per the official rules, ‘attacking’ and ‘blocking’ function in game terms almost identically to a status.
In particular:

Abilities that trigger when a creature (or player) attacks or blocks only trigger when a creature that was already in play becomes an attacking or blocking creature (that is, they trigger on the state transition into a state of ‘attacking’ or ‘blocking’). This means, for example, that if you attack an opponent with Kaalia of the Vast and use her triggered ability to put Aurelia the Warleader into play tapped and attacking, Aurelia’s triggered ability that triggers when she attacks will not trigger that turn.
Costs associated with attacking or blocking are also evaluated in the same way. This means for example that someone who is attacking an opponent with an animated Den of the Bugbear when that opponent controls a Ghostly Prison only needs to pay for the Den of the Bugbear that they are attacking with, not the Goblin token that gets created.

The second point is what is relevant here. Tapping a creature is part of the standard cost of attacking with that creature, so it gets ignored if some alternate cost is paid, or if something completely circumvents the cost (as is the case with any effect that puts a creature or creature token into play attacking). This is actually why cards that put creatures into play attacking also put them into play tapped, because that provides consistency with how the rest of the game works without making things even more complicated.

This particular aspect of attacking and blocking also has a third implication, namely that abilities or spells that say that a creature is attacking or blocking ignore costs associated with the action of attacking or blocking. This is why the ‘Goaded’ keyword, as well as creatures like Juggernaut explicitly state ‘if able’ in their effects. Without that, such effects would allow you to circumvent additional costs imposed on attacking or blocking (such as by the aforementioned Ghostly Prison).

I think "becomes an attacking or blocking creature" in the first bullet point is potentially confusing. It's more accurate to say that those abilities trigger when a creature is declared as an attacker or blocker. This is how it is described in the rules, e.g. in 508.3a. Also, since you are trying to describe this distinction between "declared as an attacker" and "enters the battlefield attacking", it's a little confusing to use the word "attacking" in both cases in the second bullet point.

It's also misleading to refer to tapping as a "cost" to attack. Tapping the creature is simply part of the action of declaring an attack. It doesn't follow any of the rules about costs, and there is no such thing as an "alternate cost" to attack. In addition, I think your final paragraph doesn't really add clarity about the interaction between attacking/blocking requirements and costs. You don't really make it clear why the "if able" clause affects that interaction in that way, and you don't address restrictions at all, even though they play a major part.

Actually, I have another thing: one issue with categorizing attacking/blocking/neither as a status is that rule 110.5c doesn't really apply to it. All actual statuses are only ever directly changed by spells, abilities, or turn-based actions, but a creature can be removed from combat by a much more complicated sequence of actions, e.g. after a spell resolves, a state-based action causes a creature to die, which causes a continuous effect to end, causing a creature to change control, which removes it from combat. (i.e. Lightning Bolt hitting a Willbreaker controlling an attacking creature).

@murgatroid99 re 509.6 and "doesn't say that that triggers abilities": I believe you are misreading/misunderstanding things. Both 509.5a and .5b say that a creature that blocks outside of normal declaration of blockers will still trigger effects (if that creature was not already blocking; it's the transition to a blocking state that matters).

OK, you're right about that part. I didn't notice those rules. I've deleted my comment about that.


text:
Will Bioviosionary and Mirrorweave always end in a draw if every player has 4 or more creatures?
I have the following scenario:
Player A: Has 4 creatures on the board, one of them is Biovisionary.

At the beginning of the end step, if you control four or more creatures named Biovisionary, you win the game.

Player B: Also has 4 creatures on the board.
Player A draws Mirrorweave and plays it on his turn.

Each other creature becomes a copy of target non-legendary creature until end of turn.

So first I fought Player A should win because it is his end step, but referring to this question here At the beginning of the end step" meaning and comparison to "your end step" and "each end step, the end step means any players end step.
Therefore, both Player A and B have 4 “Bioviosionary” that say at any end step you win the game.
In my understanding this scenario will always end in a draw, or does it matter on which step Player A is playing “Mirrorweave”?

The last player in turn order with 4 or more creatures on the board will win, so if Player A plays Mirrorweave on their own turn Player B will win.
As per 603.2b when the end step begins all the Biovisionaries will attempt to add their abilities onto the stack, this is done in the standard APNAP order.
During Player A's end step as the active player they will add 4+ copies of the if you control four or more creatures named Biovisionary, you win the game ability onto the stack, then Player B will add 4+ copies of their own onto the stack.
Then as per 405.5 the top ability will resolve first, winning the game for Player B

Note that Mirrorweave is an instant, so if Player A is smart, they'll play it during B's turn and win.

And of course, in a multiplayer game, APNAP order means that the right-most player with 4 "Biovisionaries" would have the trigger resolve first and win the game.


text:
Can Dauntless Bodyguard give a land indestructible if it was animated previously?
Say I have a Shambling Vent. I animate it, then play Dauntless Bodyguard targeting it. At the end of turn, Shambling Vent returns to being a land. Next turn, opponent uses a land destruction spell on Shambling Vent. Can I sacrifice Dauntless Bodyguard to give Shambling Vent indestructible, thereby countering the land destruction spell?
Relevant text of Dauntless Bodyguard:

Sacrifice Dauntless Bodyguard: The chosen creature gains indestructible until end of turn.

The question hinges on whether this ability still works given that Shambling Vent isn't a creature at the time Dauntless Bodyguard is sacrificed.

Possible duplicate: Kaya The Inexorable with Luxior, Giada's gift

Yes, it can. As long as the first ability of Dauntless Bodyguard resolved at a time the land was also a creature, it will track that permanent.

700.7 If an ability of an object uses a phrase such as “this [something]” to identify an object, where [something] is a characteristic, it is referring to that particular object, even if it isn’t the appropriate characteristic at the time.

You're right about the rules but I think your conclusion is wrong. In the OP's scenario, Shambling Vent has already stopped being a creature when the ability is activated.

In the example provided along with rule 700.7, a delayed triggered ability that references "that creature" is created, and it works even if that object is no longer a creature by the time the ability triggers. The instance in question is about an activated ability instead of a delayed trigger, but otherwise it's essentially the same issue. The important thing is that the referenced object is defined earlier, and the later ability still refers to the same object.

@Andrew How does rule 700.7 not apply here? The characteristic of "creature" has been removed, but the object was previously chosen.


text:
Request for clarification on section 107.1b of the Comprehensive rules (Numbers and Symbols)
In section 107.1b of the Comprehensive rules there is an example where power and toughness of a creature change in a way that I find confusing.
Example: Chameleon Colossus is a 4/4 creature with the ability “{2}{G}{G}: Chameleon Colossus gets +X/+X until end of turn, where X is its power.” An effect gives it -6/-0, then its ability is activated. It remains a -2/4 creature. It doesn’t become -4/2.
I don't understand why the creature doesn't become a -4/2 creature. In my mind the creature has a base power and toughness of 4/4 which is first modified to -2/4 and subsequently to -4/2 (for a duration). It would seem to me that the only way for the power and toughness values to not change is if X is zero or the effect from the ability is ignored for some reason. But X is not zero since the base power has changed from 4 to -2. Neither is there a reason to ignore the effect from the ability.
Is the meaning of the text that a creature can "become" something else if it undergoes a change in characteristics which is separate from the creature being subject to modifier values that cause a temporary change in the interpretation of it's characteristics? In the example the base power and toughness of the creature is 4/4, which are modified by the first effect to -2/4, changing the characteristics of the creature? The Colossus thus "becomes a -2/4 creature". There is then the effect from the activation of the creature's ability which causes a temporary interpretation of the characteristics to -4/2 until end of turn. In this sense the creature "doesn't become -4/2" since the characteristics do not change from -2/4 but are merely subject to a temporary modifier value.
I'm a new player (haven't even played a game yet) trying to get an overview of the rules, so I might not be using the correct terms ("effects", "characteristics", "objects").

The reason is rule 107.1b itself:

Most of the time, the Magic game uses only positive numbers and zero. You can’t choose a negative number, deal negative damage, gain negative life, and so on. However, it’s possible for a game value, such as a creature’s power, to be less than zero. If a calculation or comparison needs to use a negative value, it does so. If a calculation that would determine the result of an effect yields a negative number, zero is used instead, unless that effect doubles or sets to a specific value a player’s life total or the power and/or toughness of a creature or creature card.

Adding to power and toughness does not fall under any of the exceptions, thus 0 is used instead of −2.
(Under some earlier versions of the rules, the exceptions were different and did include this case of adding to power and/or toughness; it would have become −4/2 under those versions of the rules.)

I still don't follow. Take the calculation to determine the new power. This calculation adds -2 to -2, yielding the answer -4.  Following the logic of the paragraph quoted:  whenever the calculation needs to use a negative number (-2), it uses it. ("If the calculation needs to use a negative value, it does so"). But this yields a negative number, -4. Then the rule tells us: "zero is used instead". I am not clear what this means: 0 is used instead of the answer, or 0 is used instead of one/both of the negative inputs. (cont...)

(...cont) It seems there are 3 options. (a) 0 is used instead of the answer. We end up with 0 power. (b) 0 is used instead of both the -2s in the calculation. We still end up with 0 power. (c) 0 is used instead of just one of the -2s in the calculation. We would end up with -2 power. But this again "yields a negative number", so we should replace the other -2 by 0 also, and we're back in case (b). Whichever way I try to construe this, I seem to end up with 0 as a result.

OK, I think I see what is happening. "Calculation that would determine the result of an effect" here means "calculation of the amount by which the power will change", not "calculation of the eventual power". That's quite a confusing use of English - "result" of something normally refers to the situation after that thing has been applied.

@James The calculation is "add -2 to the creature's power". You can't add a negative number to power, so you add zero. The same way, you can't gain negative life, or draw negative cards.

@doppelgreener Where does the rule say you can't add a negative number to power? It explicitly says you can use a negative number in a calculation: "If a calculation needs to use a negative number, it does so".

It's the next sentence: that you'd add -2 power is the calculation. I don't know what else to tell you.

@doppelgreener Your comments don't seem to agree with each other. According to your second comment, the relevant calculation (which we don't accept a negative answer to) is "determine what number to add to the creature's power", not "add -2 to the creature's power". Is that right?

@JamesMartin Buddy I have not figured out the best way to explain the rule but I'm doing my best here. I think you're overthinking it. If something tries to add some amount of power but the amount we add is going to be negative, we add zero. That's all.

@doppelgreener I very much appreciate the help! Definitely didn't mean to suggest otherwise. Clearly you are right about what the outcome is. The question is: why does rule 101.7b have that outcome? Probably I'm hung up on something here, but the sticking point does seem to be what the meaning is of "calculation that would determine the result of an effect". I'm sure someone will come along and clear everything up in due course :)

The text of Chameleon Colossus's ability is "Chameleon Colossus gets +X/+X until end of turn, where X is its power." The calculation that would determine the result of the effect is calculating the value of X. If that calculation results in a negative number, 0 is used instead.

Also, for context, they changed this rule a few years ago to prevent Death's Shadow from getting buffed beyond 13/13 when its controller has negative life. Death's Shadow has the ability "Death's Shadow gets -X/-X, where X is your life total." And again, the relevant calculation is the calculation of the value of X.

OK I see, interesting! Thanks @murgatroid99 and all.

@m90 But in the example given with the rule the text says "An effect gives it -6/-0". In my understanding this would translate to "4 + (-6) = -2", which would be a calculation determining the result of an effect yielding a negative number.

@ doppelgreener You said that "You can't add a negative number to power, so you add zero". But that's what the text from the example seems to do as I showed above. Also, as m90 said, under some earlier versions of the rules the creature would have become -4/2. That is, the calculation would have been "-2 + (-2) = -4".

I'm also inclined to agree with James Martin that interpreting the phrase "Calculation that would determine the result of an effect" to mean "Calculation of the amount by which the power will change" seems confusing. Does the substitution of the variable for its value determine the result of the larger expression more than the larger expression itself? One variable is just one term of an expression after all.

Also it seems to me that the effect does in fact double the power of the creature. The card text says "Chameleon Colossus gets +X/+X until end of turn, where X is its power”. Increasing something by the value it has just means doubling of the value.


text:
When naming a card, can you name a card that doesn't exist?
Inspired by the new card You Are Already Dead.
There's a combo deck that wins with Thassa's Oracle, then playing Spoils of the Vault in response to the Oracle's trigger to exile their entire library. The win is deterministic - once Spoils resolves the game is over. Opponent probably won't concede though, since they get to see what else is in the deck for sideboarding equity.
One consequence of this is that when naming a card with Spoils of the Vault, it's become rather common to name You Are Already Dead, since the opponent really is "already dead". It's a way to poke fun at them and/or to tilt them.
Question: are you allowed to name even more stupid, non-existent card names like "I'm Still At 20 Lol" or "Your Wife Is Cheating On You" to tilt them even more?
NB: for the combo to work, one needs to name a card not in the deck. You Are Already Dead is such a card, and other silly card names won't be in the deck either.

Technically the opponent can stifle the oracle trigger after spoils resolves, so it isn't a deterministic kill in many formats. E.g. Overcharged Amalgam can do it in (2022) standard

awwww would've been a great loophole like vertical castling

@Caleth yes but it's unlikely - the combo is a top-tier combo and the only "commonly-played" card that can stop it is Stifle itself, but Stifle isn't even among the top 50 most-played Legacy spells right now (https://www.mtggoldfish.com/format-staples/legacy/full/spells). These spells also require mana to cast, and it's possible opponent either doesn't have the mana, or if they have the mana, then one can decline to combo.

Am I missing something? It seems like this combo kills you before you get a chance to win the game.

@ArcanistLupus you need a third card to keep yourself alive - typically Phyrexian Unlife or Angel's Grace.

@ArcanistLupus you aren't drawing from an empty library, you are looking at the top X cards of an empty library, changing the order of those cards, and then winning, all in one ability

@Caleth: Spoils is the part that would kill you. You lose 1 life for each exiled card, so you need some way to survive that.

As an aside, the very similar Demonic Consultation/Oracle combo in Vintage used Abandon Hope for this purpose before You Are Already Dead was printed.

The trick is to rename your ___ to whatever name you want to use.  It doesn't even need to be in your deck!

You have to name a card that exists.

201.4. If an effect instructs a player to choose a card name, the player must choose the name of a cardin the Oracle card reference. (See rule 108.1.) A player may not choose the name of a token unless it’ s also the name of a card.

For further explanation of what may or may not be named, here's a rather comprehensive article on magicjudges.com on the subject.

What if the card exists, but just not in your deck?  That's all this exploit requires.  You could just pick something common and obvious like "Forest" if you know there's no green in your deck...

@DarrelHoffman the combo as described names a card not in the deck. That isn't in question

This is 201.4 in the latest CRs; whatever site you are using for your rules reference is out of date.

Thanks for the note @PhilipKendall, I actually got it from https://blogs.magicjudges.org/rules/cr201/

@DarrelHoffman a ruling for Spoils of the Vault is "You don't have to choose the name of a card that's still in your library, or even a card that's in your deck at all. If no card with the chosen name is in your library, you exile your library and lose 1 life for each of those cards."   https://gatherer.wizards.com/Pages/Card/Details.aspx?name=Spoils%20of%20the%20Vault


text:
How come Ceta Disciple is a merfolk?
The Oracle text of Ceta Disciple marks it as a merfolk, although the card as printed clearly doesn't say it's a merfolk. How come it's a merfolk?

The only thing I can think of is there was an errata that turned all wizards into merfolk, although that is surely nonsense given how many wizards there are.

During the Grand Creature Type Update, all creatures got a race. Ceta Disciple is even mentioned in that article (but no reason):

2) Creatures that lacked races got a race. The vast majority of these are creatures that should be Human but were printed before Mirrodin. In fact, more than half of the cards involved in this update got "Human" added to them. Some cards got other races, like Dryad (Dawnstrider), Dauthi (Dauthi Marauder), Soltari (Soltari Crusader), Thalakos (Thalakos Sentry), Kor (Silkenfist Fighter), Merfolk (Ceta Disciple), and so on.

I guess it just looks like a Merfolk? And it's not the only Merfolk in that set:

Reef Shaman
Tidal Courier
Vodalian Mystic
Whirlpool Rider

Those cards were all printed as Merfolks. So making Ceta Disciple a Merfolk is certainly not off-theme.

Reef Shaman also looks to have acquired a profession at the same time, mirroring Ceta Disciple from the other direction


text:
Why don't bridge players try to surprise their opponents by learning a different bidding system?
Sort of a follow-up question to Why don't the meanings of specific bids need to be considered when giving advice?
As I understand the answers to that question, most bridge players play variants of the same bidding system. In other words, most bridge players have lots of experience playing with and against that bidding system.
Given that, why don't some bridge players learn a new bidding system to catch their opponents off-guard? You don't have to come up with a brand new bidding system; just pick one of the many currently listed on Wikipedia. Even though bridge bidding systems are public knowledge, by using the new bidding system:
You:

Are playing a system you are familiar with
Are playing against a system you are familiar with

Your opponents:

Are playing a system they are familiar with
Are playing against a system they are unfamiliar with

This seems like an advantage. Certainly something similar applies in Magic: the Gathering (which is the other card game I'm most familiar with) - there is some value in bringing a rogue archetype to a match, because opponents are less likely to know what to do against it. The question becomes whether the advantage you gain from that is worth the rogue archetype (probably) being weaker than the top archetypes. In Magic, the answer is usually 'no', but presumably that does not apply to bridge (since if the other bidding systems really are inferior to the most popular one, then everyone including top players would be using the same bidding system).

I don't know of any people that play different bidding systems, specifically to throw off opponents. But lots of people play systems such as T-Walsh that are designed to be beneficial for the pair will throw off weak opponents as a side effect. Systems such as strong club, opening transfers and many other that I can't think of right now are even more different from "standard bidding" and will also throw off good unprepared opponents.

Most players play variants of the same bidding system because learning a significantly new bidding system is a significant amount of effort.  Most players aren't very good even with the only bidding system they know.  Ask them to learn a new one and they would be perpetually confused.  Most players aren't that serious.
I'm now going to ignore the mass of non-so-good players and focus on the advanced and expert players.
In most countries, the main bridge-tournament organizing association regulates what bidding systems are allowed, precisely to limit this strategy.  You're not allowed any bidding system you want, and bidding systems and or conventions that are likely to be unfamiliar to opponents are banned, particular in games where each pair faces each other pair only for a small number of boards.  (In North America, it's quite common for good-to-expert players to complain about the regulations put forward by the ACBL on the grounds that it bans legitimately useful conventions that are not that hard to prepare for.)
In tournaments without such restrictions, which are mainly very high level tournaments such as world championships, players are required to disclose their bidding systems to their potential opponents several weeks ahead of time so that their opponents can prepare.
Even so, there are some practical reasons why bridge players don't play highly unusual systems all that often.  The first is that it is actually hard to design a good (human-playable) system that's very different from any of the commonly played systems.  (Minor variations don't do much to confuse opponents.)  If you make up a completely new system, even if you are good at it, the system is likely to have some significant weaknesses (which may simply be that it's very complicated and you need to spend a lot of mental effort remembering what your bids mean).
A second is in how professional bridge players make a living.  There is no prize money in bridge tournaments.  Rather, bridge players are paid by wealthy sponsors who want to win (or at least do well) in tournaments by having good players play as their partner.  It's unlikely that their clients want to put in the effort to learn an unusual system or that their clients will be able to play the system well.  Even the professional players who usually play with the same partner (because they are hired to be part of a team where the client plays with their professional partner at one table and two professionals play with each other at the other one) change partners sometimes when their usual partner is unavailable for a tournament (or does not want to be vaccinated and hence is taking a possibly temporary forced retirement).
(Most players at all levels play with several different partners.  I once played four different systems in a week; I can handle that but most players would be quite confused.  And there are subtle things I tend to get wrong when switching systems.)
A third is that a significant amount of bridge is played with matchpoint pairs scoring, where your score comes from how you do on each hand compared with a large number of other players.  If you are a very good player, you play the cards better than everyone else and can score 60% (which is usually close to enough to win) every hand just by being in the same contract as everyone else.  Playing a different contract than everyone else introduces additional randomness, which you don't want.  Certainly, there will be games where the hands suit your system, you get to better contracts, and score 65%.  But 60% is first, and 65% is also first, and there are also games where the hands don't suit your system, you get to worse contracts, and score 57%.  (Let's suppose your system is actually better, so you lose less when you are unlucky than you win when you're lucky.)  But now 57% is third.

To give you some idea of the difficulties of learning a different system: 4 years ago I started playing Precision with one partner.  It's very much a minority system - definitely less than 5% of partnerships play it - but the most important counter-strategy is well known - when opponents open a Precision 1C (which announces a strong hand but no other information), take additional risk to pre-empt and take away their bidding room.  It's only late last year, after maybe 2500 hands playing this system, that I feel comfortable against this counter-strategy.

Even in absence of the regulatory issues described in Alexander Woo's answer, there are reasons why this would not be an effective strategy.
There's a reason why a handful of systems have become popular. They're either

Easy to learn and remember because they don't have lots of artificial bids. Standard American, 2/1 Game Forcing, and Polish Club are examples of this.
Technically superior in finding the best contract. Precision is an example of this.

The popular systems are tried and true. If you make up your own system, it's unlikely to be better in either of these ways -- if it were, someone probably would have invented it earlier. It's not impossible that you could be a genius and make a significant improvement on a century of experience, but unlikely.
If the only important feature is that it's unfamiliar to the opponents, that's not likely to make up for its misfeatures. You won't be able to play it with many partners, so you can't get as much practice as you can with standard systems. And since it's presumably highly artificial, this means you're more likely to forget details and make mistakes using it.
Many auctions aren't even competitive, so the opponents don't need to be able to defend against your conventions. In these hands, you're likely to confuse yourself for no gain at all.
There's an inherent limit to how much artificiality you can put in a system, because you have to arrange that the auction tries to end at a reasonable contract. You can't use many bids to describe a pair of weak hands, because you'll end up too high.

I actually don't think Precision, at least the way I've been playing it, is actually better at finding the best contract!  We've been using it mostly to open lighter, to make it harder for opponents to find their best contract in more situations, without giving up too much on our ability to find the best contract.

Aggressive styles in general accomplish that -- it's also a benefit of weak and mini NT. But you're right, big club systems in general allow for systemically light openings, which has a strong preemptive effect.

Precision systems are much, much better at finding the right slam. Which doesn't matter so much at pairs, because, unless it's impossible to miss, most pairs won't bid the slam. At teams, however, it's a huge advantage.

@AlDante That's also the argument for 2/1 versus SA. The earlier you find out that you have at least enough for game, the more room you have to investigate slam.

The difference between Precision systems and 2/1 is the scope for finding out exactly what partner has. In Viking Club, for example, you can find out partner's exact distribution, aces, kings and queens below the slam level. In Power Precision you will know controls and queens, and have the opportunity to find exact holdings in a particular suit. None of that is available in 2/1, because you still get too high too early.

I'm not interested in discussion the benefits of different bidding systems.

It's been done before, just once, and very successfully.
However, no-one else is Barry Crane.
First the system: Four-card majors (Yes!) played in a very light opening and slam averse style, emphasizing in fast and out fast auctions. Plus, you had to play the cards the way Barry specified as well or he would throw a tantrum and lose on purpose.
No-one plays four-card majors any more; and not many played them during the latter half of Crane's career in the 70's and early 80's. Yet Crane won nearly as many Swiss Team events as he did Open Pairs, and one could argue that the difference is not the system, but just that Crane is only 25% of a team while 50% of a pair; he was of course a superb card player also.
Second, you have to understand just how good Barry Crane was: One of the top experts in the World, and regarded by many as the indisputably best Match-Point player ever; yet also wealthy enough to be a client. Barry liked to pick-and-choose McKenny winners, as he could usually play only two days a week, so the deal was this:

He'd pay you to play with him two days each for so many weeks - the understanding being that you in return would garner so many extra wins as to almost guarantee a McKenny win over your rivals.

Playing with Crane, however, was no picnic. Upon winning King of Bridge as a high school senior, Jeff Meckstroth was granted the "privilege" of a game with Crane. Upon its completion Meckstroth is claimed to have shredded the convention card in front of Crane while averring never to play with [Crane] again.

"No-one plays four-card majors any more" - except that Acol is "standard in British tournament play and widely used in other parts of the world" (Wikipedia).

@AdamChalcraft: Perhaps if I restated as "No-one (except ACOL-playing Brits) plays four-card majors any more"? ;-)

"It's been done before, just once, and very successfully"? Roth-Stone, C.C.Wei and Glenn Grøtheim immediately spring to mind as inventors of new bidding systems. Maurice Harrison-Gray, Jack Marx and S. J. "Skid" Simon also invented a system with four card majors, which today is played everywhere from Mumbai to Sydney and Auckland. You may have heard of it: Acol.


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How does Thespian's Stage work with Spreading Seas?
Say I have a Thespian's Stage and a Dark Depths that is currently an Island (because of Spreading Seas). What happens if I use Thespian's Stage to copy the Dark Depths?
Do I get a copy of Dark Depths, or do I get an Island? If I get Dark Depths, I assume it has 0 snow counters so I can immediately make Marit Lage. If I get an Island, does the legend rule apply? If not, does anything happen if I later destroy the Spreading Seas?

Thespian's Stage will copy the details printed on the land card being copied, these are termed the land's copiable values.
In the case of a Dark Depths enchanted by a Spreading Seas the Thespian's Stage will become an un-enchanted copy of Dark Depths, with no ice counters on it.
As Spreading Seas does not change the enchanted land's name or whether it's legendary, the legend rule will kick in, and you must choose to keep either the enchanted copy of Dark Depths, or the Thespian's Stage.

Applicable rulings from cards:
Thespian's Stage

A land's copiable values are those printed on it, as modified by other copy effects. Counters and other effects aren't copied. Notably, if you copy a land that is also a creature because of a temporary effect (such as Celestial Colonnade), Thespian's Stage will become just the “unanimated” land.

Spreading Seas

The enchanted land loses its existing land types and any abilities printed on it. It now has the land type Island and has the ability to tap to add {u} to its controller's mana pool. Spreading Seas doesn't change the enchanted land's name or whether it's legendary, basic, or snow.


text:
How does Thespian's Stage work with Urza's Saga?
Say I have a Thespian's Stage and an Urza's Saga. I copy the Urza's Saga with Thespian's Stage. It should become a Saga, if I'm not mistaken, and therefore start gaining the Saga chapter abilities. When the copied Urza's Saga hits level 3, with the trigger on the stack, I use the Thespian's Stage ability to turn the Thespian's Stage/Urza's Saga into another land. Do I still have to sacrifice the Thespian's Stage?
I'm guessing the answer is no because there's a ruling for Urza's Saga which says:

Even though Urza's Saga is a land, it is also still a Saga, and it will be sacrificed after its last chapter ability resolves.

And if I turn Urza's Saga into another land, then it is no longer a Saga (but the third chapter ability otherwise resolves as normal).

No, you won't have to sacrifice the Thespian's Stage, but it will retain both the added abilities, and the lore counters.
Rule 715.4 covers sacrificing a Saga once the number of lore counters exceeds the final chapter number, and has the requirement that the Saga permanent doesn't have an chapter ability currently on the stack, as the Thespian's Stage can respond to the triggered ability while it is still on the stack it will stop being a Saga before the final ability resolves.
Notably, because the lore counters remain, if the same Thespian's Stage was used to copy another Urza's Saga if would immediately be sacrificed.

715.4. If the number of lore counters on a Saga permanent is greater than or equal to its final chapter number, and it isn’t the source of a chapter ability that has triggered but not yet left the stack, that Saga’s controller sacrifices it. This state-based action doesn’t use the stack.

"it will retain ... the added abilities" - of Urza's Saga? How? Normally with copying cards, only abilities of the last copied card is retained.

same what NotThatGuy said. Counters stay, because the card didn't leave the field, but tehre's nothing that would say that UrzasSaga abilities stay. Just like the first time Thespian copied UrzasSaga, and his abilities have not stayed, only UrzasSaga abilities showed up. Otherwise, Thespian's text would have no point in saying that the card retains copy-land ability.

Found: 706.11 https://blogs.magicjudges.org/rules/cr706/ which says, that the effect tracks the card, with a similar example of card destruction. It mentions a condition of "referring by name", in Sagas we have "referring by type", but I'd not be picky here. However, since Saga's destruction is explicitly a state-based effect, this effect literally ceases to exist when Thespain ceases to be Saga type and can't activate. Were the mechanic a triggered effect like "after adding counter, if it exceeds limit, destroy at end of turn", it would resolve, linger, track the card, and kill it.

I believe that "it will retain...the added abilities" is referring to the abilities granted by the chapter abilities I and II, which both say "Urza's Saga gains ''". Each of those creates a separate effect that grants an ability to the permanent. Those effects are separate from the copy effect, and continue to apply after a new copy effect resolves.

Yes, because the abilities added by Urza's Saga apply in layer 6 and copy effects apply in layer 4, the abilities added by Urza's saga aren't "seen" by Thespian's Stage while the copying is taking place (this also means they don't get copied off an Urza's Saga that has had them applied)

Wait, are you saying that after Thespian's Stage copies another land, the new land still has Urza's Saga's 2nd ability (i.e. it can tap and make constructs)? If so, that sounds strong, wow.

Yes, because of the way CR 611 and CR 613 work the new land will still be granted the abilities setup while it was an Urza's Saga,
Additionally this will also function through a Blood Moon (the stage becomes a basic mountain but will still be granted the abilities), but not an Alpine Moon if it's played after the Saga abilities have resolved.


text:
What happens if you hit +20 VP and Defcon 1 at the same time?
Say you are the US, you are at +17 VP, and Defcon is at 2. You event Duck and Cover. This event says "Degrade Defcon 1 level, then US player earns VPs equal to 5 minus the current Defcon level". Do you win or lose or does the game end in a draw?
Surprisingly this doesn't seem to be in the rules, which say:

The instant one player reaches a score of 20 VP, the game is over and that player is the winner.
...
A player may also win the instant his opponent causes the DEFCON level to reach 1.

The 'then' part makes me assume it's a specific order you have to process the actions. So first the degrade -> you lose, if you didn't lose earn the VP.

@J_rite that sounds like the most natural result, but I guess I'm confused since in Magic: the Gathering, you finish resolving everything on the card first and then you check to see if a player has won (https://boardgames.stackexchange.com/questions/45331/if-i-simultaneously-kill-my-opponent-and-deck-myself-at-the-same-time-is-the-ga). If that rule also applies to Twilight Struggle, then the win/loss conditions would happen simultaneously.

I never played twilight struggle, but  this answer on boardgamegeek seems to indicate that you would lose.

Magic: The Gathering has rules specifying how and when state-based actions are checked, like ending the game.
Unless Twilight Struggle also has such a rule, and I haven't found one yet, there is no reason to assume the writers meant anything other than "instantly" when they wrote "instantly", or that the card should all happen at once when they wrote "(do this first), then (do that second)".
The sequence of events is this

The phasing player uses the card as an Event.

DEFCON is reduced from 2 to 1.

The opponent instantly wins the game because the phasing player has caused DEFCON 1 to occur.

The game is over, no other card effects matter.

BGG thread agrees: https://boardgamegeek.com/thread/2169804/article/31515755#31515755

I'm accepting this answer since I tried it in the Playdek app and the result was indeed loss by thermonuclear war.

M:TG was a specific comparison made by the question author in a comment and an implicit cause of their confusion. Addressing it directly does not harm the rest of the answer, including it makes the answer more useful for some readers (and based on post rates, a plurality of the users here will find it a net gain).


text:
What happens if you need to play Missile Envy, but cannot due to Red Scare/Purge + Quagmire/Bear Trap?
Say Quagmire/Bear Trap as well as Red Scare/Purge are currently in effect. Opponent plays Missile Envy. Now I need to play Missile Envy on my turn, but I can't discard it to Quagmire/Bear Trap because it's 1-op now and those cards require 2 ops. What happens now?

You discard different 2+ops cards until out of Q/BT, then play Missile envy.
This is a bizarre edge case. You can't play Missile Envy, thus you must play a different (2+ops) card. You must play the Missile Envy at the first AR after the Q/BT ends unless your hand is full of scoring cards.  If your hand is full of scoring cards then you can play the scoring cards and play the Missile Envy at AR1 of the next round.
Sources:

Official FAQ:

Q. How does one deal with a Missile Envy placed in one’s hand when
under the effect of a Bear Trap or Quagmire? A. A player under Bear
trap/Quagmire who has had Missile Envy played against him MUST use it
as the next discard if its value has not been degraded by Red
Scare/Purge.

reddit

This is an exception to being forced to play missile envy on your next AR.

BGG

You must play Missile Envy at the very next possible AR, if it doesn't force you to lose the game. So, if you have nothing but scoring cards and ME by the time you exit Quagmire, you play the scoring cards (you can't be forced to hold them). If Quagmire/BT lasts across a turn boundary, you must use ME on the first AR (not headline) as a discard to Q/BT.

(And, of course, if Terrorism/5YP/Ask Not/Grain Sales/etc causes ME to leave your hand, you clearly aren't forced to play it either).

twilightstrategy:Missile Envy

Wrong answer in the commnets, then ddddddd makes the correction:

... play a different card. I’m pretty sure we based this on something we read online somewhere.


text:
Can you discard a scoring card to the Space Track 6 power in Twilight Struggle?
Space Track 6 gives you this power:

Upon reaching space 6 (Eagle/Bear has Landed), the player may discard their Held Card at the end of the turn

Scoring cards cannot be held, and you are supposed to lose if you hold it at the end of the turn, but can you discard a scoring card to this power before you lose?
I'm guessing "no" since the power says "discard their Held card", implying that the scoring card is already held and therefore you lose first, but would like to confirm.

You are right, you can not discard a scoring card to the Eagle/Bear has Landed ability since you already lost if you hold a scoring card in this situation.
from reddit:

If you check the turn sequence, checking for a held scoring card comes before the end of a turn. The discard a card space race power is explicitly at the end of the turn. So, you can't discard a scoring card on the space race because you lose for holding it before being able to do so.

BGG thread agrees: https://boardgamegeek.com/thread/1381708/can-you-discard-scoring-card-if-you-have-reached-e


text:
How many cards should I draw with Potion of Luck?
The Potion of Luck says: "Instant — Destroy Potion of Luck: Shuffle your hand and arsenal into your deck, then draw that many cards". Say, I've got 4 cards in hand and one in the arsenal. Do I draw 4 or 5 cards?


text:
Has R&D explained how super-powerful cards like Oko and Uro were printed?
These past few years, there've been several ridiculously powerful cards printed in Standard that eventually got banned in Modern or even Legacy (!). Oko, Thief of Crowns and Uro, Titan of Nature's Wrath are the biggest offenders. The two cards being in the same colors led to a Pro Tour where most players maindecked four copies of Noxious Grasp. Field of the Dead and Once Upon a Time are also in the same league.
Has R&D ever explained how these cards made it through the testing process? I know they did for Skullclamp (mentioned in this answer) and also Felidar Guardian (mentioned in this MTG Goldfish article; the link there is dead but can be found at the Wayback Machine), and I'm looking for something similar for these or other Standard-banned cards.

Have a look at the rarity of the cards in question. That's why.

@ComicSansStrikephim Oko and Uro were so far beyond the power of even any other Mythic Rares. Getting banned in Legacy is quite a feat.

Mark Rosewater, the lead designer on Magic: the Gathering recently answered a related question on his Tumblr blog about the overall design philosophy that results in overpowered cards:

Question:

Banning cards is necessary but it's always a sign that something went wrong. I'd like to suggest a post/article about lessons learned from bannings. For instance, what was the goal/story of Fable of the mirror break design, what/why it went wrong and what's the lesson learned.

Answer:

Cards being banned aren’t always a sign that things went wrong. We could make a world where cards never (or almost never) get banned by never pushing boundaries, but we don’t think that would be as fun of a game.
I truly believe if nothing ever gets banned, we aren’t doing or job properly. We’re supposed to come up to the line, which occasionally means we step over it, as where exactly the line is changes based on so many conditions.

There is a play design article that addresses what happened with Oko in particular:

Alongside power level, we were working on different structures for the Food deck, moving planeswalkers around on the mana curve to react to shifting costs elsewhere in the file, and churning through a variety of designs to try and find something that had any hope of being a fun Constructed card. Earlier versions of Oko had most of their power tied up in (a much broader) stealing ability, which was even less fun for the opponent than turning them into Elk.
Ultimately, we did not properly respect his ability to invalidate essentially all relevant permanent types, and over the course of a slew of late redesigns, we lost sight of the sheer, raw power of the card, and overshot it by no small margin.

This is a very nice collection of statements. Judging by these snippets alone, it would allow for the assumption that cards are being designed with a margin for overpoweredness in mind, which would then possibly be fixed by banning cards in focus formats such as Standard or Modern. If that were the case, this means that other formats such as Commander (which isn't very trigger-happy at all as far as bans are concerned) will still have to deal with those cards. I'm not sure how great such a strategy is, especially considering that someone really should have caught Oko's general utility...

@TheThirdMan At least years back (when I was still actively playing MtG) the official WotC stance was always that they design and test cards primarily for Standard. How defensible that policy is given that Standard has long stopped being the "standard" way how most players interact with the game is a different question - but so is whether it's even possible to continuously print interesting cards without them ever breaking one of n formats. I believe that's also what Rosewater alludes to.

@TheThirdMan Also, there is the historical perspective that WotC has learned the hard way that underpowered sets are financially substantially worse for them than overpowered ones. I believe this line of thinking is what ultimately led us to the Age of Oko.

@xLeitix I'm sure that Standard is more of a measure than Commander or other formats. However, since Commander sets are produced by WotC by the many, they shouldn't completely disregard its existance either. My point wasn't and isn't to tell them what to do though, and I do see your points of course - but when they are banning cards, they confirm there's a limit to how powerful a card should get - and while I can understand missing Saheeli - but only recognizing Oko's power level after the fact (even just looking at Standard) isn't very reassuring of their dedication to balancing in my opinion

@TheThirdMan Sure, and they said they messed up. I have been following MtG since the early days, this isn't the first nor will it be the last massive balance cockup (Skullclamp was a fun and similar one, where it simply never crossed their mind that giving a creature -1 actually made it an engine by itself).

@TheThirdMan Personally, I am less concerned about individual crazy cards like Oko that they simply missed. What bothers me more is the tendency to print sets like War of the Spark, where clearly the design goal behind the entire set was to have a crazy power level. Such sets don't happen by accident, somebody decided that they want a set that roughs up every format.

@xLeitix Agreed... my concern also isn't with single cards that a person missed who tried their best but honestly missed it - my concern is that presumably for profit-before-balancing reasons. the integrity of the game as a whole (read: a large number of feeling-of-the-game-changing set releases), or at least such a change for the Commander and other eternal formats. Single cards being as blown-out-of-proportions as Oko is are simply alarmingly indicative of such changes, in my opinion.


text:
Has there ever been a deck that expects to lose game 1, then win game 2 and 3?
Per title. This kind of deck would acknowledge that its mainboard plan is not very strong, but expect that its sideboard is powerful enough to tilt games 2 & 3 in its favor. Or, phrased differently, has there ever been a deck whose mainboard plan is not very good, but whose sideboard plan is strong enough to compensate?
I'm not aware of any such deck. The two closest are:

The traditional midrange deck like Jund expects to improve against all strategies post-board since it has the tools to beat everything in its 75. However, even this kind of deck hopes to win game 1; it usually has versatile cards maindeck that can disrupt whatever it faces, and there are matchups where it is naturally advantaged.
I once conceived of a deck that would play every good card legal in the format, with something like 400 cards maindeck, then after sideboard it would board down to the specific 60 cards most effective against the opponent. Such a deck would indeed expect to lose game 1 and win games 2 & 3. However, this idea is illegal, because sideboards cannot have more than 15 cards even postboard.

I do know of decks that do the reverse - they expect to win game 1, then hope to win one of games 2 and 3. Examples would be graveyard and artifact decks. Game 1 they are devastatingly effective, but post-board they can expect opponent to have strong sideboard bullets, which makes the games much harder. Still, if they can steal one of the postboard games, they still win 2-1.

why would anyone make an intentionally weak main deck? I dont understand the assumptions behind this question.

@Hackworth two ways of interpreting the OP. The first way is that your intentionally weak main deck has a sideboard plan that trumps everything opponent might be doing. The other is that if your main deck is weak, it's not worth bothering trying to come up with a sideboard, no matter how enticing certain sideboard strategies might be.

Nobody does this, because there's mathematically always a better option.
Consider the most extreme version of your plan:  This deck has a 0% win rate in its base form, but can sideboard to have a 100% win rate against any deck - but each sideboard will only win against that particular deck, and has a 0% win rate against any other.
There's no advantage to starting in the base form, when you could instead start in the form which is effective against the most popular deck.  If deck A can sideboard into deck B or deck C, then deck B can sideboard into deck C, so there's no opportunity cost for starting in a winning configuration.
The only way starting with a bad deck could be in any way viable is if your goal is to trick your opponent into sideboarding incorrectly - but that can only ever work for a single game, as after the second game they will know your true strategy and can sideboard against it for the third.  Throwing away your entire first game for an advantage in the second is not at all worth it.
And again, that's supposing the most extreme version of your deck.  In reality, a 15 card sideboard is just not that impactful.  Realistically, there's no way to tailor a deck to your opponent's weaknesses so drastically as to turn a deck with a low chance of winning into one with a high chance of winning.  But even if you could, then you might as well start out with a chance of beating at least one deck.

I agree with you in practice, but I disagree that this is mathematically impossible. Suppose your deck had a 30% chance of winning pre-sideboard against everything, but post-sideboard was still 100% if correctly sideboarded and 0% if incorrectly sideboarded. Then it's correct to play the unsideboarded version as long as you expect the most popular deck to be less than 30% of the field -- but I still think it's reasonable to call this a deck that "expects to lose game 1".

This is not a viable strategy, for two main reasons:

The sideboard is only 15 cards, compared to the minimum 60 cards in the deck.
The sideboard needs to address multiple matchups, so only a few of those cards are useful for any given matchup.

As a result, even if you sideboard optimally in every match, the vast majority of the cards you see and play are from the main deck. This means that the rest of the deck still needs to be strong enough to win, and to support the sideboard answer you bring in so that it can actually be effective.

This is not a viable strategy in constructed formats, as the other answers have pointed out. However, in limited formats, there are usually no restrictions on the size of your sideboard, and you are allowed to include as many basic lands in your card pool as you like.
If there is a single card in your card pool that is capable of winning the game on its own in some situations, it can be viable to sideboard out your whole deck, leaving just that card and the appropriate number of basic lands, and then mulligan down to one to try to find it. Examples include Pack Rat and Lost in the Woods.
So if you were lucky and got one of those, you could play a fairly generic deck in game 1 to sound out your opponent's deck and then switch strategy for games 2-3 if you were reasonably sure they couldn't beat your silver bullet card.


text:
Magic the Gathering: Annihilator and Ashnods Altar
If an opponent attacks me with an Ulamog the Infinite Gyre and its annihilator 4 triggers on me. If I have an Ashnods Altar, will sacrificing creatures to the ashnods altar count towards the annihilator 4?

It's not quite an exact duplicate, but this is very similar to https://boardgames.stackexchange.com/q/35026/2537, https://boardgames.stackexchange.com/q/33274/2537, https://boardgames.stackexchange.com/q/27512/2537, https://boardgames.stackexchange.com/q/49126/2537. The short answer is no, if you are sacrificing something for the annihilator trigger, you are only sacrificing it for that, and not for anything else.


text:
How does Founding the Third Path work with Revolt?
Founding the Third Path's 3rd chapter allows you to cast a spell from your graveyard. Say I target Fatal Push. Can I successfully kill a 3-CMC creature with Fatal Push? In other words, does the Founding leave the battlefield first courtesy of its saga effect, or does the Fatal Push resolve first?
Relevant text of cards in question:

Founding the Third Path: III — Exile target instant or sorcery card from your graveyard. Copy it. You may cast the copy.

Fatal Push: Revolt — Destroy that creature if it has mana value 4 or less instead if a permanent you controlled left the battlefield this turn.

The saga will leave the battlefield before Fatal Push can resolve, meaning you get revolt.

715.2. A chapter symbol is a keyword ability that represents a triggered ability referred to as a chapter ability.

Abilities of sagas are triggered abilities that use the stack and have to resolve before they do anything.

715.4. If the number of lore counters on a Saga permanent is greater than or equal to its final chapter number, and it isn’t the source of a chapter ability that has triggered but not yet left the stack, that Saga’s controller sacrifices it. This state-based action doesn’t use the stack.

The saga leaves the battlefield when its final ability has finished resolving, but at that time, Fatal Push is still on the stack, waiting to resolve. By the time Fatal Push does resolve, the saga will have left the battlefield and given you revolt.

The first sentence is still wrong. It should probably say something like "The saga will leave the battlefield before Fatal Push resolves".

In theory the result could be different if a card had different targeting restrictions depending on if Revolt is enabled, but no existing Revolt card does that.