"Not make him immortal." He says straight away to clear that up. He would not wish immortality on anyone.

"Right before I showed up here they were doing experiments to try to pass on my immortality. What they were doing was choppin' my limbs off and swappin' them around with other convicts." Not a time he usually likes to dwell on for very long.

"They only got immortality if they kept my limbs. Putting back their own arms and legs? The worms lived just long enough to reattached like nothing happened, but they'd loose the immortality. I don't know exactly what makes my body so special, but the worms can't reproduce without enough of me going with them." The doctors figured it out, but they didn't share the answer with their unwilling test subject. "As long as I keep this arm attached to me for now my worms will keep it healthy and alive. Then when the time comes? There will be just enough worms transferring between us to reattach. After that? The rest of the worms in his arm would die off. Leaving him like nothing happened."

Well... "You know, besides the memory of having his arm cut off and reattached. I can't really do anything about that."