Decay Incineration

Black flames explode from a point of your choosing within 100-foot of you. Each creature in a 30-foot-radius sphere cantered on that point must make a Dexterity saving throw. A target takes 5d6 fire and 5d6 necrotic damage on a failed save, or half as much damage on a successful one.

The black flames spreads around corners. It ignites flammable objects in the area that aren't being worn or carried.

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.