Arcing Smite

Your weapon arcs with magical electricity. Your next melee attack during the duration deals an additional 4d6 lightning damage. For the rest of the duration the creature hit by the spell arcs with magical electricity, and at the start of each of it's turns it spreads this effect to other creatures of your choice within 15 ft. of the affected creature (no action on your part). Creatures that this effect spreads to take 2d6 lightning damage, and continues to spread the effect. If the spell ends then the effect ends on all creatures affected.