You channel lightning into your hands. The next time you hit a creature with a melee attack (including a melee spell attack) before the start of your next turn, the target takes 1d12 lightning damage and must make a Constitution saving throw. On a failed save, the target becomes shocked, stunning them until the start of their next turn.
The spell ends after dealing damage, or at the start of your next turn, whichever occurs first.
Using a Higher-Level Spell Slot: The damage increases by 1d12 for every slot level above 1.