Arc Lightning

Your inner energy swells and arcs out your outstretched finger onto one or more target creatures. The target creature and each creature (excluding you) within 5ft of it must make a Dexterity saving throw. A creature takes 3d6 lightning damage on a failed save, or half as much damage on a successful one.

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the damage increases by 1d6 and the range of additional targets increases by 5ft for each slot level above 1st .

E.g. If cast at 3rd level the target creature and each creature within 15ft would make the dexterity saving throw, suffering 5d6 damage on failed save or half that on a successful one.