Disrupting Shoal
Betrayers of Kamigawa — Rare
Instant — Arcane
Disrupting Shoal rulings:
2018-12-07: If a card in your hand has in its mana cost, X is considered to be 0.
2018-12-07: If a spell has in its mana cost, include the value chosen for that X when determining the mana value of that spell, even if it was cast for an alternative cost and no mana was spent on X.
2005-02-01: Disrupting Shoal can target any spell, but does nothing unless that spell's mana value is X.