Piège brisesprit

For Mindbreak Trap's alternative cost to apply, a single opponent must cast three or more spells. Three opponents each casting a single spell won't work, for example.

If a spell is exiled, it's removed from the stack and thus will not resolve. The spell isn't countered; it just no longer exists. This works on spells that can't be countered.

Mindbreak Trap's alternative cost condition checks whether an opponent cast three or more spells this turn, not whether those spells have resolved.