Acid Cloud

This spell calls into existence a pale green cloud of corrosive vapor at a point within range selected by the caster. The cloud is 100 feet in diameter, and inflicts 8d6 hit points of acid damage to any creature within the area of effect, unless they succeed on a Constitution saving throw for half damage.

The effect of the acid is cumulative, so each round a creature spends in the acid, they receive a penalty of -1 on their saving throw.