A beam of crackling, blue energy lances out toward a creature within range, forming a sustained arc of lightning between you and the target. Make a ranged spell attack against that creature. On a hit, the target takes 1d12 lightning damage, and on each of your turns for the duration, you can use a bonus action to deal 1d12 lightning damage to the target automatically. Note while concentrating on the spell you can only cast cantrips that do not require concentration should you use your action to cast a spell. If the target ever moves out of range of the spell it immediately ends. 

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the damage increases by 1d12 for both the initial strike and the concentrated damage for each slot level above 1st.