Is a player forced to choose a different replacement effect in order to end a (otherwise infinite) loop?

Situation: Player A controls Rest in Peace and activates his Helm of Obedience targeting player B. Player B's library contains Progenitus, and player B decides to shuffle it back. Soon the library will contain only this card, and the activated ability will only finish resolving when player B decides to exile the card instead of shuffling it back. But then, the game would be lost for him.

CR 716.4 (“If a loop contains only mandatory actions, the game is a draw.”) is not applicable, as there is a choice. CR 716.6 is about loops with effects that say “(A) unless (B),” where (A) and (B) are each actions, so this doesn't help either.

Closest is CR 716.5 saying “No player can be forced to perform an action that would end a loop other than actions called for by objects involved in the loop.” Well, Progenitus definitely is an object involved in the loop, calling for an action. But the rule's wording is only about “what's not”, not giving an instruction for the opposite case (see my first question). Or is it just my inferior knowledge of the English language?

Player B is forced to make another choice and to ultimately exile Progenitus.

Player A suggests a shortcut which contains the loop (Progenitus is revealed and shuffled back in, repeat). When suggesting the shortcut, he has to describe a set of actions which are 1. deterministic and 2. end up with a player having priority. Therefore, he can't suggest to endlessly shuffle Progenitus back in, he must suggest a number of times we do that and then the other choice (exile it) is taken. Player B can agree or can choose to exile Progenitus earlier (or not agree at all, but then he might be falling into Slow Play). That's by rules 716.2a and b.

Daniel Kitachewsky
L3, Paris, France
Rules Netrep

Thank you Daniel, and I might add that CR 716.2c would be essential to your suggestion too, as it says that “the player who now has priority must make a different game choice than what was originally proposed” if he shortened the original proposed shortcut.

However, the described case is somehow trickier. CR 716.2a allows “the player with priority” to suggest a shortcut. While the loop does contain moments where a player has to make a choice, it all happens during the resolution of a single activated ability where no player receives priority. And it isn't clear that resolving this ability would end in a loop before it actually happens. As no player receives priority any more, it seems impossible to suggest a shortcut by the rules.

Well, 716.2c doesn't really play a role here since Player B doesn't have priority the moment he makes a choice.

The rules for loops are a bit fuzzy because they can't possibly cover all cases, but the general spirit is “you can't make an infinite loop containing a choice, you have to stop at some number.”

Daniel Kitachewsky
L3, Paris, France
Rules Netrep

Mmh, first you say CR 716.2c doesn't play a role because of the lack of priority, and then you give to understand that the “spirit” of CR 716.2a does apply despite the lack of priority…

Nevertheless, I take your answer for granted, thank you. I would appreciate if the rules would also cover those cases when a loop doesn't involve players getting priority. I think that shouldn't be too difficult, e. g.

716.2a At any point in the game, the player with priority (or any player, if the game is in a loop that doesn't involve players getting priority) may suggest a shortcut by …

Why exactly is there a choice here? This actually happened to me the other night, and I thought the game ended in a draw because Progenitus' ability is not optional.

Also, for what its worth, I am not even entirely clear on exactly why Progenitus' replacement effect takes precedence over Rest in Peace. Is it simply because progenitus would never actually go to the graveyard, or is this a time stamp issue?

When two replacement effects impact the same object, the controller of said object can choose which replacement effect to use, making the other one obsolete. Considering you have the choice to exile the card with Rest in Peace's ability in stead of that of Progenitus, you have to make it to break the loop.

Edited Jona Bemindt (March 11, 2013 06:21:31 PM)