Ashe's Potent Pesticide

A poison cloud seeps forth and spreads within a 20-foot-radius sphere centered on a point you choose within range. The cloud spreads around corners, and it lasts until the spell ends.

When a creature moves into the spell’s area for the first time on a turn or starts its turn there, that creature must succeed on a Constitution saving throw or take 3d10 poison damage, and it becomes poisoned. Creatures with the swarm type have disadvantage on this saving throw. 

The poisoned condition caused by this spell goes away when the spell ends.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d10 for each slot level above 3rd.