Gallifreyan Cyber Fleet

In an alternate timeline where Rassilon gave the Cybermen the means to conquer all of time and space, the Gallifreyan Cyber Fleet was an army of Cybermen and Cyber-ships that invaded the Capitol on Gallifrey.

Structure
The Gallifreyan Cyber Fleet was comprised of hundreds of Cyber-ships (COMIC: Supremacy of the Cybermen) that resembled the somewhat cylindrical Cyber-ships used by the spacefaring Cybus Cybermen, (TV: The Pandorica Opens) and particularly the Cybermen of the Cyber Legions. (TV: A Good Man Goes to War) The Cybermen that served as the fleet's soldiers, who numbered in the thousands, (COMIC: Supremacy of the Cybermen) were identical to the evolved Cybermen of the Cyber Legions that fought in the Cyber-Wars (PROSE: Ghost in the Machine) and their aftermath. (TV: Nightmare in Silver)

From Rassilon's perspective, he served as the overall commander of the Gallifreyan Cyber Fleet after being converted into the Cyber-President, declaring to the Twelfth Doctor that "the Cybermen bend their knee to [him]". However, after the Cybermen betrayed Rassilon and wired him into a Loom inside the chamber of the Eye of Harmony, the Gallifreyan Cyber Fleet's true leader revealed itself: a highly-advanced Cyber-Controller, who usurped Rassilon's plan to accelerate the end of the universe and shape the next universe in his image, instead intending to create the "Age of the Cyberiad". (COMIC: Supremacy of the Cybermen)

Origins
In an alternate timeline, Rassilon, following his exile from Gallifrey by the Twelfth Doctor, discovered an asteroid colony of Cybermen at the end of the universe. Rassilon, inspired by the Cybermen's desire to survive in a dying universe, discussed with the colony's Cyber-Leader a means of invading the Capitol on Gallifrey, as well as all of time and space. The Cyber-Leader accepted Rassilon's proposition, and had the ex-Lord President of the Time Lords converted into the Cyber-President.

Invasion of Gallifrey
The Cybermen were then organised into the Gallifreyan Cyber Fleet and travelled to Gallifrey, before commencing a full-scale attack on the Capitol; despite the Time Lords' fleets of Battle TARDISes, the Cybermen's attack was a complete success, as Rassilon and the Cybermen managed to reach, and hijack, the Eye of Harmony, killing every single TARDIS in the process. Whilst the fleet surrounded the Capitol from above, an army of thousands of Cybermen attacked from ground-level and gained access to the city. Meanwhile, Rassilon and his personal guard of Cybermen transmatted to the Capitol directly and killed the General's platoon of soldiers; Rassilon killed the Lady President with a staser and reclaimed his gauntlet, before ordering the Cybermen to capture the Time Lords in the Capitol and to take them to the Eye of Harmony's chamber, where they were placed in perpetual regeneration to harvest the Time Lords' regeneration energy via the chamber's Looms into the Eye of Harmony. The General, pursued by Cybermen, escaped into the Undercity and rounded up as many survivors as she could find into the Tomb of Rassilon, the only location on Gallifrey that the Gallifreyan Cyber Fleet could not breach. During the Gallifreyan Cyber Fleet's invasion, the Twelfth Doctor, unable to land his TARDIS on Gallifrey or contact the High Council due to Rassilon's interference, reached the Capitol from Karn via the Sisterhood of Karn's backdoor, after the Cybermen commenced an invasion of Karn. Upon arrival, the Doctor was confronted by Rassilon and his Cybermen guards, and learnt of how the Gallifreyan Cyber Fleet came to be; shortly after, a squad of Time Lord soldiers transmatted into the room and destroyed Rassilon's Cybermen, before transmatting out with the Doctor and escaping to the Tomb of Rassilon. However, the Doctor allowed Rassilon access to the Tomb shortly after, intending to learn more of Rassilon's plan.

The Cybermen and Rassilon took the Doctor and the General to the Eye of Harmony's chamber, where the Cybermen forcefully wired the General into a Loom and harvested her regeneration energy. Rassilon then revealed his plan to the Doctor: to ignite the Eye of Harmony at the exact moment the universe died, using the regeneration energy within to shape the next universe in his own image. However, the Cybermen then betrayed Rassilon and wired him and the Doctor into a Loom each, harvesting their regeneration energy. The Gallifreyan Cyber Fleet's Cyber-Controller then revealed itself and stated that the Cybermen would usurp Rassilon's vision, intending to mould the next universe into the "Age of the Cyberiad". When Rassilon's regeneration energy readings fluctuated, the Cybermen cyber-converted the Doctor and used his mind to focus the energy in the Eye of Harmony.

Erasure
With mere seconds until the collapse of the universe, the Cybermen activated the Eye of Harmony, only for the Doctor and Rassilon - who had secretly retained their individual consciousnesses within the Cyberiad - to hijack the Cybermen's plan, sending the regeneration energy backwards through the Eye of Harmony rather than forwards. This resulted in the energy travelling back in time through the Cyberiad, which now dominated all of history, and restoring the original timeline. As a result, the Gallifreyan Cyber Fleet ceased to exist, along with the rest of the alternate timeline. (COMIC: Supremacy of the Cybermen)