Davriel Cane

+1: Each player puts the top four cards of their library into their graveyard.
-2: As an additional cost to activate this ability, pay 5 life. Create a 5/5 black Demon creature token with flying.
-7: Exile all cards in all graveyards. You may then cast any number of instants or sorceries exiled this way without paying their mana cost.