原文To determine the difference between the spell's mana value and the nonland card's mana value, subtract the smaller of those two numbers from the larger one, using the mana value of the spell you cast as it existed on the stack and the mana value of the nonland card in exile. For example, if you cast Photon Blast Barrage (a sorcery with mana cost X ) and choose 2 as the value of X, its mana value is 4. If you then exile Living Laser (a Villain with mana cost 4 ), you'll compare its mana value (which is 5) to the mana value of Photon Blast Barrage (which was 4), getting a result of 1.