Toxrill, the Corrosive

•At the beginning of each end step, put a slime counter on each creature you don't control.
Creatures you don't control get -1/-1 for each slime counter on them.
•Whenever a creature you don't control with a slime counter on it dies, creature a 1/1 black Horror creature token.
{u}{b}, Sacrifice a Slug: Draw a card.