Ball Lightning

A bright streak flashes from your pointing finger to a point you choose within range and then blossoms with a crackle into an explosion of electrical energy. Each creature in a 20-foot-radius sphere centered on that point must make a Dexterity saving throw. A target takes 8d6 lightning damage and is stunned until the end of its next turn on a failed save, or half as much damage on a successful one and is not stunned.

The electricity spreads around corners. 

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.