The 'Controller Cyborg' is a Pfhor cyborg mastermind in charge of the Sph't compiler slaves. It only appears in the marathon level Pfhoraphobia, where you have to kill it, to get the Compilers to rebel against the slavers. It was guarded by a lot of Pfhor and S'pht.
The cyborg appears as a once pfhor-like being that's been mechanized. His face has the three eyed pattern of the Pfhor (in a triangle pointing down like most Marathon 1 Pfhor). But for the rest is completely robotic.
It also never moves, not even when shot. Neither does it attack the player. And it's very easy to kill it, succumbing after a few pistol shots.