Arc

You emit a crackling burst of electricity towards a creature you choose within range. Make a ranged spell attack against the target. On a hit, the target takes 1d8 lightning damage. On a roll of an 8 on the d8, lightning then arcs to one other creature of your choice within 10ft of the target. That creature then takes 1d8 lightning damage, after which the lightning ceases to arc.

This spell's damage increases by 1d8 to both targets when you reach 5th level (2d8), 11th level (3d8), and 17th level (4d8), and the lightning arcs to the second target on a roll of an 8 on any of the d8s.