The Sanctuary of Faces

Whenever a creature an opponent controls dies and would be put into a graveyard, you may spend X, where X is equal to the creature's converted mana cost, and have The Sanctuary of Faces exiles it instead.
{w/b}{w/b}{w/b}: Target creature you control becomes a copy of a creature card exiled by The Sanctuary of Faces until the beginning of the end step on your next turn.