Dark Calamity

Delve (You may exile any number of cards from your graveyard as you cast this spell. It costs 1 less to cast for each card exiled this way.)
Cumulative upkeep: Exile two cards from your graveyard or library.
Dark Calamity has the keyword abilities of creatures in your graveyard and it's power and toughness are equal to the number of cards you own in exile.