Venomous Burst

.A roiling sphere of venomous energy forms in your hand, hissing like a coiled serpent. You hurl this sphere to a point you choose within range, where it erupts in a burst of toxic green smoke and writhing spectral snakes.

Each creature in a 20-foot-radius sphere centered on that point must make a Dexterity saving throw. A target takes 8d6 poison damage on a failed save, or half as much damage on a successful one. The toxic fumes linger briefly, filling the area with a sickly green mist, and each creature that failed the initial save must also succeed on a Constitution saving throw or be poisoned until the start of your next turn

Using a Higher-Level Spell Slot. The damage increases by 1d6 for each spell slot level above 3.