Cyber-Controller (Supremacy of the Cybermen)

At the end of the universe, a Cyber-Controller ruled an asteroid colony of Cybermen. In an alternate timeline, Rassilon approached the Cybermen to propose an alliance, but the Cyber-Controller kept its existence hidden from Rassilon, allowing him to believe he commanded the Cybermen in their alliance to conquer Gallifrey, and by extension, all of time and space. Eventually, it revealed itself to the Twelfth Doctor after the Cybermen attempted to harvest the regenerative energy of the Time Lords, and revealed its plans to rebirth N-Space as the "Age of the Cyberiad".

Biography
The Cyber-Controller ruled a colony of Cybermen that existed at the end of the universe. When Rassilon, exiled from Gallifrey by the Twelfth Doctor, landed his bowship at the Cybermen's asteroid colony, the Cyber-Controller kept its presence secret from Rassilon as he consulted the Cyber-Leader over his plan to make the Cybermen the dominant species across all of time and space. After Rassilon was converted into the Cyber-President, he assisted the Cybermen in forging the Gallifreyan Cyber Fleet to invade Gallifrey, with a particular focus on the Capitol. While the Cybermen made use of Time Lord technology to gain complete dominance over the past, the Cyber-Controller allowed Rassilon to believe he was in charge until the final stages of the Cybermen's plan were ready to be enacted.

After Rassilon, the Twelfth Doctor and the General arrived at the chamber of the Eye of Harmony, the Cybermen eventually betrayed Rassilon and forced all three Time Lords into Looms to harvest their regeneration energy. However, the Cyber-Controller then intervened with a new strategy, explaining to the Doctor that the Cybermen intended to ignite the regeneration energy inside the Eye of Harmony at the exact moment the universe would end, rebirthing N-Space as the "Age of the Cyberiad", a reality which would be dominated by an ultimate evolution of Cybermen from its very beginning. Noting that Rassilon's regeneration energy readings were too unstable to complete the Cybermen's plan, the Cyber-Controller ordered the Doctor plugged in as a substitute, with the two Time Lords eventually being upgraded.

As the universe began to rapidly collapse, the Cyber-Controller ordered the activation of the Eye of Harmony to create the Cybermen's ultimate reality. However, the stored regenerative energy began flowing backwards. It was then that the Doctor and Rassilon revealed that, despite their conversions, they had retained their consciousnesses and had altered the Eye of Harmony's protocols from within the Cyberiad. With regeneration energy flowing throughout the Cyberiad, which now spanned the whole of history, the Cybermen's conquest of time and space was reversed. The Cyber-Controller, who was directly exposed to the Eye of Harmony, was engulfed in regeneration energy as it screamed in despair, shortly before the timeline reset. (COMIC: Supremacy of the Cybermen)

Appearance
The Cyber-Controller's brain was visible through a glass covering on its helmet. It lacked side handles on its helmet, instead possessing a pair of large blank, metal panels where a human's ears would normally be. Additionally, the Cyber-Controller lacked a chest unit or any other kind of external bodily components or mechanisms, aside from a thin, vertical oval-shaped light on its chest that varied between being blue and white in colour. Its body was also significantly more muscular than most Cybermen. The Cyber-Controller's face featured bright, white eyes with blue highlights, and lacked the "tear-drop" on the corners that were commonly seen on other Cybermen. (COMIC: Supremacy of the Cybermen)

Personality
Although the Cybermen were emotionless, (TV: The Age of Steel, et. al) the Cyber-Controller was highly arrogant, regarding Rassilon as "the puppet" in the Cybermen's plans, despite his integral role in the Cybermen's ultimate conquest of time and space. The Cyber-Controller also viewed Rassilon as weak, arguing that he was unable to see beyond his ambitions of godhood in the next universe; when Rassilon's regeneration energy readings fluctuated, the Cyber-Controller did not consider him necessary, noting that the Twelfth Doctor was a far more effective substitute in the completion of the Cybermen's plans.

When the Cybermen activated the Eye of Harmony, the Cyber-Controller proudly proclaimed, "It begins!", while standing in a victorious posture, but screamed in frustration and despair when the Doctor was able to undue its plans. (COMIC: Supremacy of the Cybermen)