Mercurial Geists [Mystery Booster]

Set: Mystery Booster Type: Creature — Spirit Rarity: Uncommon Cost: {2}{U}{R} Flying Whenever you cast an instant or sorcery spell, Mercurial Geists gets +3/+0 until end of turn. "Procedural misstep: provocation of geists for the purpose of yielding more energy can compromise containment units. Next action: clean up mess." —Laboratory notes