The Sewer Nexus

When The Sewer Nexus enters the battlefield,
choose X creature types.
Creatures you control are the chosen creature
type or types. The same is true for creature spells
you control and creature cards you own that
aren't on the battlefield.
{x}{x}{x}, {t}: Put X +1/+1 counters on each
creature you control that is a chosen creature
type, and put X -1/-1 counters on each
creature that isn't a chosen creature type.