Demise's Retribution

"Everything has a shadow - something that follows its every motion, acts as it does.  Do you think it gets sick of having to do that, all day every day?  Wouldn't it be nice to give it a way to vent?"

As an attack comes your way, you raise its shadow and grant it a measure of physical form as you reverse it.  Whatever attack this was taken as a reaction to is performed by you, with the same to-hit bonus, damage, and effects.  The one difference is that it deals psychic damage instead of the original damage type.