Ashiok, Calamitous Nightmare

+1 : Each opponent mills two cards.
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+0 : Exile up to four cards from a single
graveyard.
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-3 : You may cast a creature card exiled with Ashiok without paying its mana cost. If you do, it becomes
an Elemental Nightmare in addition to it’s other types and enters with a finality counter on it. ——