Belchball

A disgusting gas flashes from your mouth to a point you choose within range and then blossoms with a low roar into an explosion of vomit and gas. Each creature in a 20-foot-radius sphere centered on that point must make a Dexterity saving throw. A target takes 9d6 poison damage on a failed save, or half as much damage on a successful one.

The gas spreads around corners. 

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for each slot level above 3rd.