Kos, Great One of the Depths

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, create a 1/1 black slug creature token.
{u}{b}, Sacrifice a Slug: Draw a card.
"A bottomless curse, a bottomless sea. Source of all greatness, all things that be."
-Baneful Chant