Baneblade
Weapon (any sword), uncommon (requires attunement)
Once on each of your turns, when you hit a creature with this magic sword you can curse it until the end of its next turn. Whenever the cursed creature makes an attack roll or a saving throw, the creature must roll a d4 and subtract the number rolled from the attack roll or saving throw. This curse has no effect on a creature under the effect of the bane spell. A remove curse spell ends this effect and grants the target immunity to the sword’s curse for 24 hours.
As the jagged, inky-black sword pierced into her side, Ofélia actually felt her life essence escaping. The sharp pain between her ribs was diminished somehow. Rather, a hollow ache spread from the wound, draining her will to fight and muddling her mind. The deathless creature advanced, its lipless grin shining in the moonlight as it cackled and stabbed wildly. Just barely did she manage to disarm the thing and flee before its shambling pursuit could catch her again.