Dr. Dabrius, the Black Death

First strike, Deathtouch
{2}{b}: Put a Contagion counter on target creature.
Whenever a creature with a Contagion counter
deals combat damage to another creature, put a
Contagion counter on that creature if it had none.
At the beginning of your upkeep, each creature
with a Contagion counter gets a -1/-1 counter.
Whenever a creature gets a -1/-1 counter, its
controller loses 1 life.