Acid Flood

You create a pool of acid taking up a 20 feet area. When a creature ends a turn, enters, or exits the area it must succeed on a DC 15 saving throw or it takes 2d10 acid damage. On a success, the target takes half the damage.

The damage increases by 1d10 at 9th level to 3d10, 13th to 4d10, and 17th to 5d10.