Telos

The planet Telos was homeworld of the Cryons. It was also inhabited by the Cybermen, who used the technology of the Cryons to entomb themselves in suspended animation inside the Cyber-tombs for centuries.

Characteristics
A world that began with "Tel", before Red Rocket Rising's Acting President Eileen Klint's message was cut off, existed on the edge of Red Rocket Rising's solar system. (AUDIO: Blood of the Daleks) Following Cybermen occupation, Telos was a grey, barren, rocky world. Diamonds, vastial and other minerals could be found on the planet. (TV: Attack of the Cybermen)

History
At one time Cryons, who died instantly when exposed to temperatures above zero degrees, lived on Telos. The Cryons moved under the surface when it became too warm, constructing underground cities refrigerated to the sub-zero temperatures the Cryons needed to survive. After the destruction of Mondas in 1986, (PROSE: Attack of the Cybermen) the Cybermen later came to steal the refrigerated cities to use as repositories of Cybermen cryonically frozen in suspended animation. The Cybermen killed most of the Cryons. (TV: Attack of the Cybermen)

The Cybermen from Lonsis were twice destroyed by the Eighth Doctor. It seems after Mondas was destroyed, the Cybermen moved to Lonsis, planning to invade Earth. They were foiled by Charley Pollard, who infected their ship with temporal corrosion, and later the Doctor, who increased the range of a Quantum Crystalliser programmed to destroy them. The few survivors of these attacks colonised Telos, while Cybermen from other parts of the universe colonised other planets. (AUDIO: Human Resources)

Earth forces launched a final assault on Telos at the end of the Cyber-Wars and the planet's surface was bombarded. (AUDIO: Last of the Cybermen)

Five hundred years after the last known encounter between humanity and the Cybermen, an archaeological expedition from Earth, led by archaeologist Parry (but financed and masterminded by Kaftan and Eric Klieg of the Brotherhood of Logicians), landed on the planet to find the Cybermen and to revive them. With the Cybermen as their army, the Brotherhood planned to impose a regime of pure logic on human society. The Cybermen and their leader, the Cyber-Controller, were resurrected. The Second Doctor was able to seal them back inside their "tombs" and to electrify the outside gates. (TV: The Tomb of the Cybermen)

The Cyber-Controller was not killed, as the Doctor had believed, but survived, and had installed a base, known as Cyber-Control underground, supervising operations in 1985 London, with which they had a communications link, and fighting the Cryon rebels who remained. The Cybermen at this time employed work parties of humans whose conversions were unsuccessful as slaves to mine the surface of the planet. The Cybermen intended to destroy Telos and to observe its blast pattern for future research. The base was, however, invaded and destroyed by the Doctor (now in his sixth incarnation) with the assistance of the captured Cryon leader Flast. (TV: Attack of the Cybermen)

After the Hotel Historia on Earth was invaded by Graxnix, manager Majenta Pryce decided to flee and relocate to somewhere like Telos, claiming that it could use a little remodelling. (COMIC: Hotel Historia)

The Eleventh Doctor later revisited Telos while trying to save Billy Jones, who had been scattered through time. At this point in time, the Cyber-tombs had returned to their multi-tiered appearance, and had become occupied by Cybus Cybermen, who began to wake from the tombs. (GAME: The Mazes of Time)

The Twelfth Doctor sent "Lumpy" there to retrieve one of the pieces of the Orb of Fates, which was hidden in some ice. Once the piece was taken, the Cybermen attacked Lumpy. (GAME: The Doctor and the Dalek)

Eventual Fate
At some point during the early 26th century, Telos was destroyed by an asteroid impact. (AUDIO: Telos)

Other references
The Second Doctor offered to show River Song "this cool place on Telos." (GAME: The Eternity Clock)

The renegade Time Lady Iris Wildthyme once claimed to have visited the Cyber-tombs on Telos. (PROSE: The Scarlet Empress)

Facing the Cybermen on a Mondasian colony ship, the Twelfth Doctor recalled Telos as one of the worlds where they rose, and that he had defeated them there by sealing them into their ice tombs. (TV: The Doctor Falls)