Thunder Storm

Black clouds gather above as a storm appears in a location you choose within range. The area of the storm consists of up to ten 10-foot cubes, which you can arrange as you wish. Each cube must have at least one face adjacent to the face of another cube. Each creature in the area must make a Dexterity saving throw. It takes 5d12 lightning and 2d8 thunder damage on a failed save, or half as much damage on a successful one.