Phyrexian Mollusk

Infect (This creature deals damage to creatures in the
form of -1/-1 counters and to players in the form of
poison counters.)
Whenever Phyrexian Mollusk deals combat
damage to a player, you may sacrifice a creature.
If you do, put a +1/+1 counter on Phyrexian
Mollusk.
In the bowels of Phyrexia, a hideous fusion of metal
and flesh crawls forth, harvesting life.