Thunderstruck

You focus on a creature, and a storm cloud appears above that creature's head. Once this spell has been cast, anytime this target takes damage from a metal weapon a bolt of lightning will strike the target where the weapon hit. The target will take 1d8 lightning damage, but if they succeed a dex saving throw they will take half damage.

counter spell ends this effect.

At Higher Levels.

You gain an additional 1d8 per spell level cast