Ball Lightning

A ball of lightning hurtles in a curved line 60 feet long and 10 feet wide blasts out from you in a direction you choose and then blossoms with a low roar into an explosion of electricity. Each creature in the line and each creature in a 15-foot-radius sphere centered on the end point of the curve must make a Dexterity saving throw. A creature takes 8d6 lightning damage on a failed save, or half as much damage on a successful one.

The lightning ignites flammable objects in the area that aren't being worn or carried.

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.