Ball of Lightning

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 light. Each creature in a 20-foot-radius sphere centered on that point must make a Dexterity saving throw. A target takes 4d6 lightning damage on a failed save, or half as much damage on a successful one.

Targets within 10 feet of a target will be hit with Lightning chain receiving half damage (does not chain to targets hit already)

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the damage increases by 1d6 for each slot level above 2nd.