1 Feb 2005
Disrupting Shoal can target any spell, but does nothing unless that spell's mana value is X.
7 Dec 2018
If a spell has {X} 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.
7 Dec 2018
If a card in your hand has {X} in its mana cost, X is considered to be 0.