Mephidross Megalith

{t}: Return target creature card from your
graveyard to the battlefield tapped. You get
poison counters equal to that card's converted
mana cost. Put a -1/-1 counter on that creature
unless you sacrifice Mephidross Megalith.
If a creature with a -1/-1 counter on it would die,
exile it instead.
Both a monument to Phyrexia and a wellspring for its wretched unlife.