Insatiable Biomass

Insatiable Biomass's power and toughness are each equal to the number of creature cards in your graveyard.
Whenever a creature you control dies, put a +1/+1 counter on Insatiable Biomass.
{b/g}{u/b}: Remove a +1/+1 counter from Insatiable Biomass, put a -1/-1 counter on target creature you don't control.