Scion of Decay

{p/b}, {t}, Sacrifice this card. Your opponent loses X life and you gain X life where X is the total Black Mana Symbols among permanents you control.
When this creature died, if you controlled another Black creature, search your Library for a 'Scion of Rot', reveal it, then place that card onto the Battlefield tapped.
"I've never seen so much sickness in one area before. What foul magic is responsible?" - Gregor, Death-Hunter