Springheel Blade (5e Equipment)
From D&D Wiki
Weapon (shortsword), uncommon (requires attunement by a creature missing some or all of a leg)
This hook-shaped prosthetic leg has a thin blade in the center that runs from a spring-loaded mechanism at the top, through a hole in the bottom of the hook. While the prosthetic is attached and attuned to you, you can use the weapon as if you were holding it. It otherwise functions identically to the leg it is replacing. You can detach or reattach it as an action, and it can't be removed by anyone else.
If you have multiple springheel blades, they count as a single magic item with regard to the number of magic items you can attune to.