Arcane Affliction

The first time you hit with a melee weapon attack during this spell's duration, a beam of crackling, blue energy forms a sustained arc of lightning between you and the target. The target  has to make a Constitution Saving Throw or take an extra 1d6 of lightning damage, and become stunned until the end of your next turn. On a successful save, the target takes half damage and is not stunned.

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