Acid Mire is a daily power available to Wizards at 5th level[AP]
Acid Mire
Wizard Attack 5
You transform the ground beneath your enemies' feet to hellish slime that eats away at flesh and bone.
Daily ✦ acid, arcane, implement, zone
Area burst 1 within 10 squares
Target: Each creature in burst
Attack: Intelligence vs. Fortitude
Hit: 3d6 + Intelligence modifier acid damage
Miss: Half damage
Effect: The burst creates a zone of caustic slime that lasts until the end of your next turn. The zone is difficult terrain. Each creature that enters the zone or starts it turn there takes 5 acid damage. Whenever a creature falls prone within the zone. it takes 5 extra acid damage.
Sustain minor: The zone persists