Lifeless Lich King

+2: Sacrifice any number of DeathKnights you control, Gain life equal to the total mana value of each creature sacrificed this way
-3: Exile any number of DeathKnights you control, Gain life equal to the total power and toughness of all creatures exiled this way
-7: Mill any number of cards from your library, Gain life and mana equal to the total number of cards milled this way