Let's say an opponent has hexproof due to Leyline of Sanctity. Can I still cast a spell like Thoughtseize against them, just to let it fizzle and trigger prowess?
3 Answers
No, you can't. Part of the process of casting a spell is checking whether it's legal to cast:
601.2e The game checks to see if the proposed spell can legally be cast. If the proposed spell is illegal, the game returns to the moment before the casting of that spell was proposed (see rule 725, “Handling Illegal Actions”).
If any chosen target is illegal, the game reverts to its state right before you started casting Thoughtseize, so Prowess never triggers.
-
2You could, of course, cast Thoughtseize targeting yourself, but that seems suboptimal unless the prowess trigger will immediately win you the game. Aug 29, 2020 at 15:44
-
1@Caleth A) thoughtseize isn't a search effect, so fail to find doesn't apply, B) even if it did, you would still lose 2 life and reveal your hand, which is still suboptimal though not as bad. Sep 16, 2021 at 13:30
Casting a spell requires a legal target which a player with hexproof is not (according to the comprehensive rules):
702.11c “Hexproof” on a player means “You can’t be the target of spells or abilities your opponents control.”
Your example would work if the opponent becomes an illegal target while Thoughtseize is on the stack.
Whether the targets of a spell are legal is checked both at the casting and at the resolution. "Fizzle" refers to when a spell's targets are valid at the time of casting, but become invalid by the time of the resolution. A spell whose targets are not valid at the time of casting does not "fizzle", it simply is not cast at all.
