Eldritch Burn

Your sword glows with a bright green flame the target must succeed a Dexterity saving throw (DC = 8 + Your proficiency bonus + Charisma modifier) or take 1d6 necrotic damage on a failed save or on a successful save they take half as much. If you use a third level spell slot or higher  add an extra 1d6 for each level spell slot used beyond 2nd. The martials use to cast this spell is one melee weapon in which you are proficient with.