Zaru, God of Plagues

If your combined devotion to black, red and green is more than 10, creatures you control get +0/+1 and gain poisonous 3. (Whenever it deals combat damage to a player, that player gets three poison counters.)
{1}{b}{r}{g}: Until end of turn, if an opponent would get a poison counter, they get two instead.
A sickness to blanket the lands in my beautiful and twisted image.