Veronica's Venom Storm

A dull green glow appears from your pointing finger and at a point you choose within range, then blossoms with a low roar into an explosion of venomous smoke. Each creature in a 10-foot-radius sphere centered on that point must make a Constitution saving throw. A target takes 6d8 poison damage and becomes poisoned for 1 turn on a failed save. A creature cannot regain hit points while poisoned in this way. They take half as much damage and are not poisoned on a successful one. 

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d8 for each slot level above 3rd.