Death Lightning

You create a storm of Death lightning, bolts striking in a 30-foot radius around you. Each creature in the area that you choose must make a Dexterity saving throw. On a failed save, a creature takes 8d6 lightning damage and suffers one level of deathblight (Exhaustion).
For the duration, mist of deathblight fills the area. Each humanoid other than you that ends its turn in the mist must make a Constitution saving throw or suffer one level of deathblight (Exhaustion).
At Higher Levels.
When you cast this spell using a spell slot of 8th level or higher, the damage increases by 1d6 for each slot level above 7th.