If I cast Glasspool Mimic targeting a Lord of Atlantis that I control, and in response to the spell going on the stack, my opponent casts Petty Theft targeting the same Lord of Atlantis, how would this resolve?


3 Answers 3


Firstly, Glasspool Mimic does not target; quoting from its Oracle text:

You may have Glasspool Mimic enter the battlefield as a copy of a creature you control, except it's a Shapeshifter Rogue in addition to its other types.

You do not have to choose the creature it is copying until it actually enters the battlefield. You can choose any creature you control at that point, and your opponent does not get to respond to the choice as this does not use the stack.

If you have no other creatures available when the mimic enters the battlefield, it enters as a 0/0 creature and will be moved to the graveyard the next time state-based actions are checked unless there is some other effect increasing its toughness.


Glasspool Mimic doesn't target. Its ability is a replacement effect that replaces the event of it entering the battlefield with the event of it entering the battlefield as a copy of another creature, and the choice of what creature it copies is made at the moment the event is replaced. If you were to cast it and say that you were targeting Lord of Atlantis, this would probably be interpreted as an intended shortcut (it would be an improperly worded one, but a judge would probably overlook that) for casting Glasspool Mimic, and then, on resolution, choosing Lord of Atlantis as the creature to copy.

Your opponent casting Petty Theft would then be a rejection of that shortcut, which would allow you to make new choices from the moment of your opponent deviating from the shortcut, meaning that if you have any other creatures on the battlefield, you can have Glasspool Mimic enter as a copy of one of them.

Note that if you were to say "I cast Glasspool Mimic, targeting my Lord of Atlantis", and your opponent were to not do anything in response and just say "Okay", and you were to then say "Oh, whoops, Glasspool Mimic doesn't target. So I let it resolve, and then at resolution I choose another creature for it to copy", your opponent would have a case to be made that they interpreted your initial statement as a proposed shortcut, they accepted it, and now you can't change you choice.

  • While I agree with this answer technically, I feel that if it's happening at anything below Competitive REL it should be treated as a learning opportunity rather than a rules enforcement opportunity. Sep 12, 2022 at 11:24

It would stay the copy of lord of Atlantis because he would need to send back lord of atlantis to your and before glasspool mimic enter the Battlefield because as soon as it enter the Battlefield you choose wich creature you want to copy your opponent does not a word to say about that and it does not specify that the copied creature need to stay in the Battlefield

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  • While MtG does have some situations in which the last known characteristics of an object are used, this is not one of them. Petty Theft is being cast in response to the mimic being cast, not to it resolving, so the Lord of Atlantis is not on the battlefield as it resolves. Sep 11, 2022 at 5:39

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