Vuldur, Cursed Mind

Exploit (When this creature enters the battlefield, you may sacrifice a creature.)
When Vuldur, Cursed Mind exploits a creature, each player puts the top seven cards of his or hers library into their graveyard.
Whenever an opponent puts a card into their graveyard from their library or hand, if it's a creature, that player loses life equal to half it's converted mana cost rounded down.