Voltwire

You conjure an electrified wire in a 20 foot by 5 foot line leading away from you in a direction you choose. When a creature starts its turn in or mves into an area occupied by the wire, that creature must succeed on a Dexterity saving throw or take 1d8 lightning damage.

 After a creature takes damage in this way or if you lose concentration on the spell, the wire dissipates and the spell ends. 

This spell's damage increases by 1d8 when you reach 5th level (2d8), 11th level (3d8), and 17th level (4d8).