Moravia, Ever Devouring Flame

When this card enters the battlefield, you can sacrifice {x} permanents.
Flying, haste, indestructible, shroud, annihilator {x}, where {x} is the number of sacrificed permanents.
When this card attacks you can mill {x} cards.
If you milled more than 40 cards, defending player takes 40 damage and his or her creatuers can't block this turn.