Anubis' All-Encompassing Lightning

You fling red lightning at a target, where it immediately branches off and attacks nearby foes. Make a ranged spell attack against one target in the range. On a hit, you deal 3d8 lightning damage. Then, attack every other creature or object of the caster's choice within 15 feet of the original target using the first attack roll, but roll damage for each separately. Until the spell has no more targets within 15 feet of a previous target, continue attacking. A creature or object can be targeted by this spell only once per casting, and all targets must be within 120 feet of the caster.