Acid Rain

Acid rain begins falling within a 30-foot-radius 40-foot-high cylinder centered on a point you choose 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 8d4 acid damage, and becomes covered in acid. A creature covered in acid takes 1d4 acid damage at the end of their turn for each time they have failed a saving throw against this spell.

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

Source: Kibble's Generic Elemental Spells