Whenever an opponent casts a spell, you may reveal the top card of your library. If you do, counter that spell if it has the same converted mana cost as the revealed card.
Illustrated by Joseph Meehan
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Notes and Rules Information for Counterbalance
- If an opponent casts a spell with X in its mana cost, the converted mana cost of that spell takes the value of X into account. If you reveal a card with X in its mana cost, X is 0. For example, if your opponent casts Blaze with X=1, Counterbalance will counter that spell if you reveal a card with converted mana cost 2, but it won’t counter that spell if you reveal a Blaze of your own. (2006-07-14)
- If an opponent casts half of a split card (for example, Hit), and you reveal a split card where half of it has the same converted mana cost (for example, Hit/Run or Stand/Deliver), Counterbalance will counter the spell. (2006-07-14)