Closed Circuit

You raise one arm while clutching your arcane focus or the material component and from it, lightning arcs from you in a 20 ft. radius. Each creature in the area must make a Constitution saving throw. A creature takes 7d6 lightning damage on a failed save, or half as much damage on a successful one. Additionally, until the end of your next turn, you are immune to lightning damage.
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.