demon core

from where you are pointing your finger a bright blue flash of burning light appears in a point you choose within range and then blossoms into blinding sunlight before vanishing. Each creature in a 20-foot-radius sphere centered on that point must make a concertino saving throw. A target takes radiation as 6d6 necrotic damage on a failed save, or half as much damage on a successful one.

the hit points lost to this attack can not be regained from healing, only a long rest.

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.