Gyox, Brutal Carnivora

Legendary Creature — Phyrexian Warlock — {1}{B}{G}

At the beginning of your end step, put an oil counter on up to one target creature. Whenever a nontoken creature you control with one or more oil counters on it dies, conjure X duplicates of it into exile, where X is the number of oil counters on it. Those duplicates perpetually get +X/+X. Then shuffle those duplicates into your library.