Acid Surge

This spell is from the Dark Souls spell collection.

You create a 20-foot-radius sphere of green, corrosive gas centered on a point within range. The cloud spreads around corners, and its area is heavily obscured. The cloud lingers in the air for the duration.

Each creature that is completely within the cloud at the start of its turn must make a Constitution saving throw against acid. On a failed save, the creature's AC is immediately reduced by 1 and it takes 3d4 acid damage. At the end of its next turn, it also takes 1d4 acid damage.

A moderate wind (at least 10 miles per hour) disperses the cloud after 4 rounds. A strong wind (at least 20 miles per hour) disperses it after 1 round.