Cradle of Despair

Cradle of Despair enters tapped unless you put the top 15 cards of your library into your graveyard.
Whenever a card is put into a player's graveyard, you may put the top three cards of your library into your graveyard to put that card into exile instead.
{t}: Add {b} to your mana pool for every 3 creatures in exile.
It's not a place for good people.