Combat Cyborgs were NPCs, part living creatures, part droids, working for Valorum/General Grievous. Or, as he would put it, they were " Cyborgs. Under! MY! COMMAND!! "
Revelation of the Sith Edit
When Obi-Wan, Anakin, and Palpatine were trying to make their way to the hangar of Count Dooku's dreadnought, they got caught in a force field trap. R2-D2 ran into them, almost literally, as in a blind panic he ran straight into a wall. Some combat droids arrived and took all of them prisoner.
The droids took the prisoners to their droid leader, General Grievous, and the droids presented Grievous with Obi-Wan and Anakin's laser swords. When Obi-Wan referred to Grievous' "droids", Grievous corrected him. Inside each of these casings was an organic brain, that the "droids" were actually Cyborgs. "Cyborgs. Under. My. COMMAND. Upon hearing this familiar phrasing, Obi-Wan realized that Grievous was the former Chancellor Valorum. Grievous claimed that old name no longer had any meaning to him. Valorum/General Grievous claimed he had ways to improve R2's robotic body. At first, R2 liked the idea until Grievous explained that his idea of improvement was a brain transplant. Grievous intended to give R2's robotic body Obi-Wan's cerebral cortex and Anakin's amygdala. R2 panicked, and tried to zap at Grievous with his ineffective shock probes. This provided Obi-Wan and Anakin with the distraction they needed to use Force Pull to retrieve their laser swords and destroy all of Grievous' Combat Cyborgs and Magnaguards present.
Obi-Wan later arrived on the planet Utapau and confronted Grievous. Grievous was unsurprised to see Obi-Wan, and began monologuing. Two Magnaguards were present along with a few Combat Cyborgs. The Magnaguards interrupted Greivous' monologue, declaring their willingness to take on Obi-Wan. But Grievous was so enraged that they interrupted his monologuing, that he threw a huge weight on them, crushing them to death. The Combat Cyborgs decided to stay out of this, and retreated.