Cylo was a humanoid male doctor who cybernetically enhanced himself into an immortal system capable of assuming another body when the previous one died. A scientist who believed that evolution was only possible for the universe if organic species were upgraded with cybernetics, Cylo dedicated his research to this goal. Having gained support from the Separatist-leaning Astartes of Celanon prior to the Clone Wars, he subsequently entered the service of Galactic Emperor Sheev Palpatine after the war ended with the Republic’s victory and the inauguration of the Galactic Empire. For twenty years, the doctor worked to develop cybernetically-enhanced individuals who, without the need for the Force, could potentially replace Palpatine’s apprentice, Darth Vader, as enforcers for the Empire.
In the wake of Vader’s failure to stop the Rebel Alliance victories at Yavin 4 and Cymoon 1, the Emperor approved Cylo’s plans to test his apprentice. Intrigued by his Master’s mysterious new agent, Vader hired bounty hunter Black Krrsantan to track him down and discover the nature of his work for the Emperor. Captured and interrogated by Vader’s agents, Cylo revealed the location of his research base before his fourth body died as a result of torture droid 0-0-0‘s lethal interrogation techniques. With the death of this body, Cylo-V was activated. Shortly after he awoke, Vader launched an assault on his base in order to eliminate the potential competition for his place as the Emperor’s enforcer. Cylo broke off the fight between Vader and two of his enhanced subjects, Morit and Aiolin Astarte, and revealed his plans to the Sith Lord. The Emperor soon arrived, demanding a test of Cylo’s subjects. Sufficiently impressed, Palpatine declared that he would have missions for all of them but that only one would win his favor and a place at his side.
Appointed to serve in the Imperial Military at the discretion of Grand General Cassio Tagge, Cylo’s subjects served as operatives in the Empire’s escalating war with the Rebel Alliance and various uprisings against the New Order while the doctor also served as a consultant. When the nobility of the mining world of Shu-Torun rose up against the Imperial-backed government of Queen Trios, the Emperor gave command of the military intervention to Vader while Tagge sent Cylo and his subjects to support the war effort. Frustrated with Vader’s dismissal of him and determined to knock him out of the competition for a place as the Emperor’s enforcer, Cylo conspired with the rebellious ore-dukes to isolate and kill the Dark Lord. Once his plans were discovered by the Sith Lord, Cylo and his remaining subjects were forced to flee, having been exposed as traitors.
As Vader tracked Cylo to the Crushank Nebulae, the scientist used the opportunity to launch an attempted hijack of the Executor, a Super Star Destroyer that he and the other scientists of the Tarkin Initiative had helped build. The Emperor, who had ordered Vader to destroy Cylo following the revelation of his treachery on Shu-Torun, was present to oversee the final stages of the new flagship’s construction, making Cylo’s attempt an effective coup against the Empire. However, Vader overcame all the assets Cylo sent against him, eliminating both his remaining subjects before confronting Cylo and his remaining clone bodies onboard his whale-ship and using a mind trick on the creature’s brain to force it into a nearby sun. As Vader made his escape, Cylo’s last remaining clone body desperately tried to change the whale-ship’s course, burning up along with it when they crashed into the sun.