Ashiok's Will

Search target player's library for a creature card and exile it face down. If Ashioks Will was cast from your graveyard, instead you may turn a creature card exiled with Ashiok face up. If you do, put that creature card into play under your control. It is a nightmare in addition to its other types. Sacrifice it at the end of turn.
Flashback {2}{u}{b} (You may cast this card from your graveyard for its flashback cost. Then exile it.)