Arc Lighting

You brandish the weapon used in the spell’s casting and make a ranged attack with it against one creature within range. On a hit, the target suffers the weapon attack’s normal effects, and you can cause lighting to leap from the projectile to a different creature of your choice that you can see within 15 feet of its path. The second creature takes lightning damage equal to your spellcasting ability modifier.

At Higher Levels. At 5th level, the ranged attack deals an extra 1d6 lightning damage to the target on a hit, and the lighting damage to the second creature increases to 1d6 + your spellcasting ability modifier. Both damage rolls increase by 1d6 at 11th level (2d6 and 2d6) and 17th level (3d6 and 3d6).