$8.43 @ TCGplayer
You may exile a blue card with mana value X from your hand rather than pay this spell's mana cost.
Counter target spell if its mana value is X.
If a card in your hand has {X} in its mana cost, X is considered to be 0.
If a spell has {X} in its mana cost, include the value chosen for that X when determining the converted mana cost of that spell, even if it was cast for an alternative cost and no mana was spent on X.
Disrupting Shoal can target any spell, but does nothing unless that spell’s converted mana cost is X.
