Warden Page 390 (Patreon)

Runes like semiconductors are made with tiny micro channels and cannot be replicated by those of this world. Which means the Prisoner has an superhuman amount of control in his left arm. I had always envisioned Aristeans as 'crude' crafters from an advanced civilization whose mission is to jumpstart 'primitive' worlds. Having an arm that is the equivalent of an overpowered laser etcher would definitely help.