Chaotic Weapon

You touch a weapon imbuing it with chaotic energy. For the duration, the weapon deals an extra 2d4 Lightning damage when it hits. While the spell lasts, whenever the wielder misses an attack using this weapon, they take Lightning damage equal to your proficiency modifier.

At Higher Levels. When you cast this spell using a spell slot of 5th or 6th level, the the extra damage increases to 3d4.
When you use a spell slot of 7th level or higher, the extra damage increases to 4d4.