Deep Magic 2 (pg. 163)
Densini's Radiance
3-level Evocation
Casting Time: 1 action
Range/Area: 120 ft
Components: Verbal, Somatic
Duration: Instantaneous
You call down an explosion of radiant fire from the heavens on a point you can see in range. Each creature in a 15-foot-radius sphere centered on that point must make
a Constitution saving throw. On a failed save, a creature takes 6d6 radiant damage and is marked with holy radiance until the end of your next turn. On a successful save, a creature takes half the damage and isn’t marked.
The next attack roll against a marked creature before the end of your next turn has advantage.
At higher levels: When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6for each slot level above 3rd.