Koh, The Face-stealer

Whenever a creature dies, you may pay {u}{b}. If you do, exile that creature.
{1}:Koh becomes a copy of an exiled creature, but retains its name and abilities
{1}{u}{b}: Exile Koh until end of turn. Koh enters to the battlefield as a copy of an
exiled creature, but retains its name and abilities