Conjure Sphere of Stars

You create a swirling spiked sphere of icy blue starlight that floats within the air chose a point within range, a 30 ft radius sphere of starlight and cold appears. As an action you can move the sphere up too 20 feet. A creature within the sphere must make a constitution saving throw on a failure a creature takes 8d8 radiant damage and 4d6 cold damage on a successful save the target takes half damage. The sphere creates bright light in a 30ft radius and dim light for another 30ft. Undead and abberations have disadvantage on the saving throw.