Lazav, Wearer of Faces is a rare Legendary Creature — Shapeshifter Detective card from Murders at Karlov Manor (MKM), collector number 318z. Current market price: — (foil $329.99), TCGplayer market prices via Scryfall.
Whenever Lazav attacks, exile target card from a graveyard, then investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.") Whenever you sacrifice a Clue, you may have Lazav become a copy of a creature card exiled with it until end of turn.