Xzurbitix's Canceling Cube

{3}{u}{u}: Exile a random card from your graveyard, counter target spell if it's converted mana cost is the same as the exiled card.
Sacrifice a creature and an artifact: You may cast target instant or sorcery card you own from exile until end of turn, if you do that spell deals damage to you equal to it's converted mana cost.
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When Xzurbitix's master mysteriously vanished, he took over as head nullcaster.