Ampira's Arcing Bolt

You hurl a crackling bolt of lightning at a creature within range. Make a ranged spell attack against the target. On a hit, the target suffers 1d6 lightning damage and you can target the bolt to arc to another creature within 10 feet of it. If the attack roll -5 would hit that creature, it also takes 1d6 lightning damage. This repeats until the attack misses or runs out of targets in range. Each creature can only be hit once.

At 5th level the damage increases to a d8. The arcing attack reduction decreases by 1 when you reach 5th level (-4), 11th level (-3), and 17th level (-2).