You create a thick, black cloud of acid droplets that burns everything inside it.

Encounter   ✦     Acid, Arcane, Evocation, Implement, Zone
Standard Action      Area burst 4 within 10 squares

Target: Each creature in the burst

Attack: Intelligence vs. Fortitude

Hit: 4d6 + Intelligence modifier acid damage.

Effect: The burst creates a zone that lasts until the end of your next turn or until you dismiss it as a minor action. The zone is heavily obscured and blocks line of sight. Any creature that enters the zone or starts its turn there takes 10 acid damage (a creature can take this damage only once per turn).

Update (2/17/2012)
Changed in December 2011 updates.

Published in Player's Handbook, page(s) 167, Class Compendium.