Poisonous Thallid

Harvest (When this creature dies, you may sacrifice any number of creatures that share a creature type with it.)
At the beginning of your upkeep, place a spore counter onto Poisonous Thallid.
Whenever Poisonous Thallid dies, place a -1/-1 counter onto all creatures you don't control for each spore counter on Poisonous Thallid.