Gyox, Brutal Carnivora

Legendary Creature — Phyrexian Warlock

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.

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