In a conversation on Discord, CryoS mentioned that his headcanon is that Pfhor juggernauts are retired senior Pfhor heroes who get the honor of being installed in this big badass cyborg body, and Pfhor drones are disgraced junior Pfhor who get decapitated and then have their brains installed into the drone hardware.
I immediately fell in love with this gruesome idea because it explains something that's long bothered me about Marathon's worldbuilding: why would a spacefaring civilization like the Pfhor bother to use slaves? Surely robots would be a lot better. One obvious answer to this is that the Pfhor reportedly have really really terrible AI, but the immediate retort to that is that they have AI good enough for drones to fly around doing maintenance and combat and such, so surely they could have simple labor-bots that would obviate the need for any slaves.
But what if they don't?
Supposing that the Pfhor "automatons" we see are actually organic brains controlling mechanical bodies perfectly squares with the Pfhor's supposed lack of even halfway-competent AI, which in turn explains why a technologically advanced civilization would use slaves.
We know that by 2794 they have cybernetic technology enough to have those cyborgs who control the S'pht Compilers, and by 2811 they have cyborg tech good enough to make the tank cyborgs out of captured Bobs. So they should be capable and willing to implant brains in metal housings to make Drones, and Juggernauts. That also explains why both of those have faces, too.
I would suspect that they probably stole this cybernetics technology from the S'pht.
