Alduin’s lightning bolt

You summon a blazing bolt of lightning from the sky that breaks into 5 spots you can see within 150 ft. Each creature within the spots of lightning must succeed a DC DEX saving throw or take 20d6 lightning plus 20d6 thunder damage on a failed save or half as much on a successful one. If the user has 60% health or below, this spell does an extra 2d6 lightning and 2d6 thunder damage