Kanthiryx, the Blight Spawn

Flying
Dethrone (Whenever this creature attacks the player with the most life or tied for most life, put
a +1/+1 counter on it.)
Infect (This creature deals damage to creatures
in the form of -1/-1 counters and to players in
the form of poison counters.)
Whenever Kanthiryx becomes blocked, proliferate.