Acid Cloud

You create a 20-foot-radius sphere of  a billowing mass of misty vapors similar to that produced by a solid fog spell centered on a point you choose within range. The fog spreads around corners. It lasts for the duration or until strong wind disperses the fog, ending the spell. Its area is heavily obscured.  It lasts for the duration or until a wind of great speed (at least 30 miles per hour) disperses it in one round. The solid fog is so thick that any creature attempting to move through it progresses at a speed of 5 feet, regardless of its normal speed. It also has disadvantage on all melee attack and melee damage rolls. The vapors prevent effective ranged weapon attacks (except for magic rays and the like). A creature or object that falls into solid fog is slowed, so that each 10 feet of vapor that it passes through reduces falling damage by 1d6. When a creature enters the spell's area for the first time on a turn or starts its turn there, that creature must make a Constitution saving throw. The creature takes 5d8 acid damage on a failed save, or half as much damage on a successful one. Creatures are affected even if they hold their breath or don't need to breathe.

The fog moves 10 feet away from you at the start of each of your turns, rolling along the surface of the ground. The vapors, being heavier than air, sink to the lowest level of the land, even pouring down openings.

At Higher Levels. When you cast this spell using a spell slot of 6th level or higher, the damage increases by 1d8 for each slot level above 5th. At Higher Levels. When you cast this spell using a spell slot of6th level or higher, the radius of the fog increases by 20 feet for each slot level above 5th.