How about a magic item today? I’ve got a few ideas…
weapon(dagger), very rare
This +1 dagger looks more like a pin as it lacks a guard and is simply a solid cone of metal ending in a infinitely small point. When wielded by an cunning swordsman, it worse than fatal learning how to twist the knife to make even the biggest opponent hurt. Once per round, it a target is struck with this weapon while the attacker has advantage, the target of the attack must make a saving throw. On a failure, the target is incapacitated for one round. On a success the target is immune for one round. The DC of the saving throw is detailed below.