Davron's Ball Lightning

A small orb of lightning forms in your hand  which you then cast to a point within range. The orb then expands into a 20ft diameter sphere of lightning energy centered on that point. Each creature must make a dexterity saving throw. Each creature within the sphere takes 7D6 lightning damage on a failed save or half as much damage on a successful one. 

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.