Arcing Smite

An arc of lightning surges out from your attack following the horizontal path of your swing. The target of the triggering attack and all other creatures within a 15 ft square originating from you and directed toward your target must make a DEX saving throw or take 3d10 Lightning damage on a failed save, or half as much on a successful save. If the triggering attack hits the target creature, that creature automatically fails the DEX saving throw.

Using a Higher-Level Spell Slot. The damage increases by 1d10 for each spell slot level above 2.