Chamelion, Hydra Agent

Supremacy (Whenever a creature you control dies,
reveal cards from the top of your library until you
reveal a creature card, you may cast that card if that creature's converted mana cost is less than the
converted mana cost of the creature that died this turn.)
Whenever a creature dies, you may have
Chamelion, Hydra Agent become a copy of that creature and gain this ability