Cyber-conversion was the physical and mental re-engineering of victims, often humanoid, into Cybermen. In an alternate universe, this was referred to as Upgrading. A similar process used by the Borg from a parallel universe was called assimilation.
Cybermen of Mondas
Cyber-conversion into Mondas Cybermen involved the replacement of body parts (including limbs, organs, and vital systems) with artificial components. (TV: Attack of the Cybermen) Partial conversion, with the victim retaining autonomy and a human identity and body parts, was possible. (TV: The Invasion)
The Cybermen would traverse the universe to find beings to convert, adding to their forces. (TV: Attack of the Cybermen) The Cybermen relied on tubing to keep the body operating, but over time the amount needed decreased. (TV: The Tenth Planet onwards)
Cybermen of Pete's World
The Cybermen of Pete's World, instead of replacing body parts, transplanted living brains into metal exoskeletons sustained in a cradle of chemicals and threaded together by an artificial nervous system. The process was extremely painful and took place in a booth where the subject's skull was sliced open by a robotic machine that used knives, lasers and syringes to remove the brain before encasing it in an empty cybernetic helmet. Later, the Ear Pods created a trance state for the victim, so they were, in a sense, unconscious during the process and unable to feel the pain of being converted. This was the most efficient form of conversion. They also had an Emotional inhibitor placed within them to suppress their humanity because, as the Tenth Doctor put it;
It's still got a human brain... imagine its reaction if it could see itself. Realise itself inside this thing. They'd go insane....
During the Battle of Canary Wharf, the Cybermen, badly needing reinforcements, quickly converted humans into Cybermen using a different method. They encased humans in cybernetic shells by constructing the suit of armour around their body, as with Lisa Hallett. Hallett would have died if her lover, Ianto Jones, had not retrofitted a cyber-conversion unit into life support for her. This form of conversion was excruciating. The subjects were heard screaming as metal was grafted onto their flesh, possibly because the Cybermen had little time to place their victims in a trance state. (TV: Cyberwoman)
- It may be that the reason certain converts with exceptionally strong willpower like Yvonne Hartman could overcome their programming was because this form of conversion was less precise and more rushed.
The Cybermen also employed a very primitive type of conversion in 1851 when they created the Cybershades using scrap metal and Victorian era human technology. They also invented a method of converting humans into command units for CyberKings by fitting them with a headset that could take control of their brains. The CyberKing was intended as a mass conversion unit, but the command unit Miss Hartigan, aided by the Tenth Doctor, destroyed it before it was put to use. (TV: The Next Doctor)
A Cyberman's exo-skeleton in 102 at Stonehenge displayed the ability to upgrade humans without any external machinery, merely needing to restrain the victim while the Cyberman's faceplate split open at the middle and enveloped the victim's head. The process from here on is unknown, as the only known victim of this process was Amy Pond, who escaped before the process was completed. (TV: The Pandorica Opens) The human that was previously converted seemed to have an upgrade like that during the Battle of Canary Wharf, due to the fact that the Canary Wharf upgrade involved encasing the body inside the suit, (TV: Cyberwoman) while this Cyberman had a severed head in its helmet. (TV: The Pandorica Opens)
Named cyber-converted individuals
Cybermen of Mondas
- Toberman- Partial cyber-conversion on Telos, regained his humanity and attacked the Cyber-Controller. Sacrificed his life to close doors of the Cybermen's tombs (TV: The Tomb of the Cybermen)
- Bates and Stratton - Cyber-conversion process failed at an early stage after their limbs had been replaced by mechanical equivalents. Put to work on the surface of Telos with similar such failures. (TV: Attack of the Cybermen)
- Lytton - Partial cyber-conversion on Telos, cyber-conversion incomplete at the time of his death (TV: Attack of the Cybermen)
- Bill (TV: Attack of the Cybermen)
- David (TV: Attack of the Cybermen)
- Evelyn Smythe (divergent timeline) (WC: Real Time, AUDIO: Real Time)
- Nicola Savage, Ricky Allen, Ryan Carey and David Isherwood (partially converted) (WC: Real Time, AUDIO: Real Time)
- Reece Goddard (skin drone; divergent timeline) (WC: Real Time, AUDIO: Real Time)
- Tobias Vaughn - Partial cyber-conversion, retained head and therefore his own thoughts. (TV: The Invasion)
- Jason Kane: After being manipulated by Irving Braxiatel, Jason was nearly converted into a cyberman. Before the conversion was complete, however, Bernice Summerfield used the energy in the Crystal of Cantus to defeat the cybermen, reversing the conversion. (AUDIO: The Crystal of Cantus)
- Webley - Partial cyber-conversion, retained most of his body.
Cybermen of Pete's World
- John Lumic - Converted into Cyber-Controller (TV: The Age of Steel)
- Sally Phelan (TV: The Age of Steel)
- Jackie Tyler of an alternative universe - Alternate counterpart of Jackie Tyler (TV: The Age of Steel)
- Yvonne Hartman - Torchwood Institute administrator (TV: Doomsday)
- Lisa Hallett - Torchwood employee and lover of Ianto Jones, partial cyber-conversion (TV: Cyberwoman)
- Mercy Hartigan - CyberKing command unit. Miss Hartigan refused to be converted to a standard Cyberman and took control of the Cybermen which landed in 1851. The Cybermen, however, had slowly set a plan in motion that would eventually make Miss Hartigan both a convert and a leader. (TV: The Next Doctor)
- Valerie Brannigan (WC: In-Flight Entertainment)