You electrify the attacker's weapon as it strikes its target. The spell deals a creature 2d6 lightning damage on a failed Constitution saving throw, or half as much damage on a successful save. If the attack was a critical hit, the damage increases by 1d6. The spell's target is determined by who made the triggering attack:
At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the damage increases by 1d6 for each slot level above 1st.