A 5-foot-diameter sphere of shimmering lightning appears in an unoccupied space of your choice within range and lasts for the duration. Any creature that starts its turn within 5 feet of the sphere must make a Dexterity saving throw. The creature takes 2d10 lightning damage on a failed save, or half as much damage on a successful one.   When you summon the sphere, choose a direction for it to move. At the start of each of your turns, the sphere moves 10 feet in that direction. As a bonus action, you can choose a new direction for the sphere to move, and it immediately moves 5 feet in that direction.   The sphere is ethereal, able to move through objects and barriers, and hovers. The sphere sheds bright blue light in a 30-foot radius and dim light for an additional 30 feet.