Colonisation of Telos

According to ArcHivist Hegelia, the colonisation of Telos was the event in which the planet Telos was seized by the Cybermen from Mondas. (AUDIO: The Cyber Nomads)

The original CyberTelosians
Even though Telos being a birthplace of the Cybermen was contentious, with Bernice Summerfield once corrected a students who said that Cybermen originated on Telos by insisting that Mondas was the true homeworld, (AUDIO: The Crystal of Cantus) and even the Sixth Doctor insisting that Telos was only the "adopted planet" of the Cybermen and that they would never have came to Telos had Mondas not been destroyed, (TV: Attack of the Cybermen) the Twelfth Doctor cited Telos, in addition to Mondas, Earth, Marinus and Planet 14, as a place where the Cybermen rose as a result of parallel evolution. (TV: The Doctor Falls)

Indeed, one account stated that the Telosian Cybermen were originally a race of humanoids, all but identical to Earth humans, native to Telos. Centuries prior to the 21st century, this race sought immortality and so perfected the art of cybernetics. As their bodies became old and diseased, they were replaced limb by limb with plastic and steel. Finally, the circulation and nervous systems were recreated, and their brains were replaced by computers, resulting in the Cybermen. (PROSE: Doctor Who and the Cybermen)

Later, forced to leave Telos, these Cybermen took refuge on Mondas, the long lost twin planet of Earth (PROSE: Doctor Who and the Tenth Planet) and the birthplace of another race of Cybermen. When Mondas was destroyed during the 1986 Cyberman invasion of Earth, (TV: The Tenth Planet) the surviving Cybermen turned their attention back towards Telos to serve as a new base of operations. (PROSE: Doctor Who and the Cybermen)

Colonisation
According to the CyberTelosians themselves, specifically the group which attacked the Moonbase in 2070, they were descended from the first space travellers from Mondas, (PROSE: Doctor Who and the Cybermen) the humanoid Mondasians having converted themselves into CyberMondasians. (AUDIO: Spare Parts) These space travellers had left before Mondas was destroyed during the Mondasians' invasion of Earth in 1986. (PROSE: Doctor Who and the Cybermen) According to yet other accounts, the space travellers had only come to Telos as a direct result of Mondas' destruction. All but wiping out the native Cryons, a humanoid species distinct from humans, the Cybermen used their refrigerated cities as repositories of their number cryonically frozen in suspended animation. (TV: Attack of the Cybermen, PROSE: Attack of the Cybermen)

According to the CyberHive history, compiled from the Cyber-Documents according to the judgment of ArcHivist Hegelia, the Cybermen did not infact seize Telos and subjugate the Cryons until after their attack on the Moonbase. Considered descendants of the early CyberFaction which left Mondas for Planet 14, these Cybermen were formally recognised as CyberTelosians by Hegelia. (AUDIO: The Cyber Nomads)

Legacy
Based from Telos, the CyberTelosians were led by the Cyber-Controller who was the mastermind at the heart of the Cybermen's empire. (PROSE: The Powers Behind the Throne)

Parallel universes
In one of the infinite parallel universes of "possible space", (COMIC: Fire and Brimstone) the last of the Cybs were forcibly interred on Telos after their planet Mondas was finally destroyed. (PROSE: The Chronicles of Doctor Who?)

Behind the scenes

 * The Discontinuity Guide places the colonisation of Telos as following both the 1986 destruction of Mondas and the failed attempt to transform Earth into New Mondas in 1988.
 * The Dead Ringers sketch "Doctor Who vs the Cybermen" has the Cybermen show the Fourth Doctor (Jon Culshaw) a picture book of some "lovely" invasions of other planets, including "Cryon". Later, after a few beers, the Doctor decides to "call it a night" after the Cybermen insist on invading Telos and converting the Cryons into "unthinking cyberdrones".