Tormentor of Sanity

{b}, Reveal Tormentor of Sanity from your hand:
Sacrifice a black creature you control. Tormentor
of Sanity's mana cost is reduced by the sacrificed
creature mana cost.
(Ex: {6}{b}{b}{b} - {5}{w}{b} => {1}{b}{b}.)
Once per turn, you may choose one card at
random from an opponent's hand. Exile that
card until the beginning of your next upkeep.
While the card is exiled, your opponents can't
cast spells with the same name as the exiled card.