Propulsion Arm

Sym-Tech Item, very rare (requires maintenance/attunement by a creature missing a hand or an arm)
To use this prosthetic appendage, you must attach it to your arm at the wrist, elbow, or shoulder, at which point the prosthetic will extend and replicate joints to form a copy of the appendage it's replacing.
While attached, the prosthetic provides these benefits:

• The prosthetic is a fully capable part of your body.
• You can take an action to remove the prosthetic, and it removes itself if your maintenance/attunement to it ends. It can't be removed against your will.
• The prosthetic is a sym-tech melee weapon with which you're proficient. It deals 1d8 force damage on a hit and has the thrown property, with a normal range of 20 feet and a long range of 60 feet. When thrown, the prosthetic detaches and propels itself towards the target of the attack, then immediately returns to you and reattaches.