This technology is referred to as a Makeyrian Soul Forge. Humanoids are stationed within capsules, similar to those needed for the Clone Spell. Their soul is then extracted from their bodies, directly into metallic shells. The shells are then pressed into a skeletal shape, infusing the body with the soul. The skeleton flow down a conveyer belt, into vats of pure arcane fluid, allowing the transfer to become permanent. The downside for the humanoid being that their souls are forever trapped within the war-forged body. The positive is obviously immortality and an upgradable body. All of this is powered by an ancient Mythilar Crystal and channeled through a helm within view. A powerful magic user has their power and mind drained from the helm, to operate this foundry. Time is shortened, depending on the other workers output within the forged, so powerful overseers are advised to look over them.