Disruption Aura | Magic: The Gathering
Formats Disruption Aura is Legal in
Official Oracle Text for Disruption Aura
Enchanted artifact has "At the beginning of your upkeep, sacrifice this artifact unless you pay its mana cost."
Official Rulings for Disruption Aura
12/1/2004 : If the enchanted artifact has X in its mana cost, X is 0.