Acid Rain

Acid rain begins falling within a 30-foot-radius 40-foot-high cylinder centered on a point you can see within range. When a creature moves into the spell's area for the first time on a turn or starts its turn there, the creature must succeed on a Dexterity saving throw or take 10d4 acid damage, and becomes covered in acid. A creature covered in acid in this way takes 1d4 acid damage at the end of each of their turns, this damage increases by 1d4 each time they fail the saving throw (to a maximum of 20d4)

A creature can spend their action to wipe off the acid clearing all stacks of acid damage.