A bright streak flashes from your pointing finger to a point you choose within range and then blossoms with a low roar into an explosion of necrotic flame. Each creature in a 20-foot-radius cube centered on that point must make a Dexterity saving throw. A target takes 8d6 fire, radiant, or necrotic damage (your choice) on a failed save, or half as much damage on a successful one. Roll two d6. For each 6 rolled, regain a fourth level (or lower) spell slot. 

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the damage increases by 1d6 for each slot level above 4th. Additionally, the maximum level of spell slot regained increases by 1 for each slot level above 4th.