R: 200 ft; T: creature; D: 0
You fire a whirling disk of force and light from your fingertip. The disk screeches like a sawblade. It deals [sum] damage to its target. If it deals more than 6 damage, it bounces towards a random creature within 20 ft, dealing [sum]-2 damage. If it deals more than 6 damage, it bounces towards another random creature within 20 ft, dealing [sum]-4 damage. This continues, losing 2 damage with each bounce, until there are no valid targets or the spell deals 6 or less damage to a creature.
The caster is a valid bounce target.