Dark Alchemy

Creatures you control have Transfigure {x} where
X is their converted mana cost. (Creatures with Transfigure have: "{x}, Sacrifice this creature: Search your library for a creature card with the same converted mana cost as this creature and put that card onto the battlefield. Then shuffle your library. Transfigure only as a sorcery.")
Whenever a creature enters the battlefield under your control, you may shuffle target creature card from your graveyard into your library.