NEK-0 Sky Fortress

Must attack, unblockable, protection from black
When this enters play, exile all cards in all graveyards. When a card would be put into a graveyard, exile it instead.
When this deals damage to a player, deal that much damage to each other creature, player and planeswalker. Whenever this deals damage to a black permanent, exile that permanent.
{x}{x}: Deal X damage to each creature or planeswalker you don't control and each opponent.