Rebounding Bolt

You fire a vibrant blue beam of energy at a creature you can see within range. The beam then bounces to a creature of your choice within 30 feet of the target, losing some of its vibrancy and continuing to bounce to other creatures of your choice until it sputters out. Each subsequent target must be within 30 feet of the target affected before it, and the beam can't bounce to a target it has already affected.
Each target must make a Constitution saving throw. The first target takes 5d6 force damage on a failed save, or half as much damage on a successful one. The beam loses some of its power then bounces to the second target. The beam deals 1d6 force damage less (4d6, then 3d6, then 2d6, then 1d6) to each subsequent target with the final target taking 1d6 force damage on a failed save, or half as much damage on a successful one.