Hapatra, Vizier of Poisons 
Legendary Creature — Human Cleric
Whenever Hapatra deals combat damage to a player, you may put a -1/-1 counter on target creature. Whenever you put one or more -1/-1 counters on a creature, create a 1/1 green Snake creature token with deathtouch.
Legality
standardNOT LEGALpioneerLEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL