Caustic cloud

Create a 20-ft-radius haze of greenish purple smoke cantered on a point you can see. The cloud goes around corners. It lasts for the duration or until dispersed with water. When a creature first enters the cloud or if it begins it's turn there It must make a constitution saving throw against your Spell DC or take 2d6 acid damage, half on a successful save. If a creature ends its turn within the cloud it must  take  1d6 poison damage, half on a successful save. 

At higher levels: The damage die increases by 1d6 for each spell level above second.