The Master

"The Master" — known in one incarnation as "Missy" (short for "Mistress"), in another as "the Lumiat", and at times by various other aliases — was a renegade Time Lord, a power-hungry "lover of chaos" who served as both a friend and the arch nemesis of the Doctor.

Friends from childhood and schoolmates at the Time Lord Academy, the divide between the Master's lust for power and the Doctor's empathy for "lesser species" would eventually pull the two farther and farther apart — to the point that the Master often sought to kill the Doctor. Despite this enmity, however, the two would on occasion act as allies, and both continued to yearn for their old friendship.

Like the Doctor, the Master fled from Gallifrey in a TARDIS of his own, and, having fully embraced his darker nature, would go on to pit himself against the Third Doctor and UNIT during the Doctor's exile on Earth. Later, having expended his original regeneration cycle, the Master survived in the ghastly form of a living cadaver, in which form he fought the Fourth Doctor, before exploiting the powers of the Source on Traken to steal the body of Tremas. He would continue his crusade to submit the universe to his will in a variety of stolen or otherwise fraudulent bodies, from using Tzun nanites in order to gain new regenerations, to transferring his essence into a Deathworm Morphant, which allowed him to survive execution by the Dalek Prelature, and continue to survive by possessing a succession of human bodies.

Finally killed by the Ravenous, the Master was eventually restored to life for good on the instructions of the Time Lords, in preparation for a future conflict with the Daleks. The Master would once again regenerate, this time into an older body that tried to manipulate the conflict to suit his own goals. However, after his failure to end the war using the Heavenly Paradigm, which had only resulted in even more devastation across the timeline, the Master was driven to such a state of terror that he fled to the end of the universe and turned himself into a human baby with a Chameleon Arch. After spending many years living as a humble human scientist on Malcassairo, the Master's personality was reawakened by Martha Jones, and, fatally shot by Chantho, he regenerated into a younger body.

Using the alias "Harold Saxon", the Master engineered his election as Prime Minister of the United Kingdom in the 2008 elections, and then sought to use the Earth to create a new Gallifrey. When his plan was foiled, he was shot by his wife, Lucy, and decided not to regenerate and die to spite the Tenth Doctor. Following a faulty resurrection by the Disciples of Saxon, the Master used the Immortality Gate to create the Master Race and attempted to free Gallifrey from the time lock of the Last Great Time War, but instead entered the last day of the war to get revenge on.

After Gallifrey returned to the universe, the Master left, and eventually ended up on a Mondasian colony ship, where he came face-to-face with a future female incarnation of himself, who stabbed him to ensure his regeneration into her. Now a woman, the Master began to call herself "Missy", the self-proclaimed "Queen of Evil". Missy went through many chaotic adventures of her own throughout the universe, but, although she loudly denied having "turned good", she demonstrated a willingness to rekindle her friendship with the Twelfth Doctor.

Eventually, Missy was captured and imprisoned inside a Quantum Fold Chamber, which was moved into a vault at St Luke's University by the Twelfth Doctor and Nardole. Although she claimed she could leave the Vault anytime she wanted to, she chose not to because she wanted to become a good person. So the Doctor tried to rehabilitate her and rekindle their friendship on his terms. On the verge of changing, Missy was sent on a trial adventure with Nardole and Bill Potts to the same colony ship her previous incarnation had regenerated on, later joining him upon realising that he had been responsible for Bill's cyber-conversion. In the end, though, she betrayed and killed her past self in order to finally stand with the Doctor, but was then killed herself in retaliation before she could return to him, with both Masters believing that this had been their "perfect ending".

Although the Master believed that the blast had disabled Missy's ability to regenerate, Missy managed to use an Elysian field, forbidden technology that could break a Time Lord's body down into atoms and molecules then reform it anew, to grant herself a new regeneration cycle and kickstart her next regeneration. Using the field, she was also able to edit her personality, distilling all the goodness within her into a new benevolent incarnation who called herself "the Lumiat". The Lumiat, whose mission it was to go back and undo the damage her previous incarnation had caused, attempted several times to change Missy's ways before she was ultimately killed by her, having grown bored of her future self. The Lumiat regenerated into a male incarnation who called himself "the Master" again, who looked down on Missy's attempts to better herself.

The Master returned to Gallifrey and discovered in the Matrix that all of Time Lord history had been "built on the lie" of the Timeless Child, which involved the true origin of the Doctor. Embittered by his discoveries, and lashing out from the belief that the Doctor had always been more than he was, the Master took his revenge on Gallifrey, leaving it in ruin. He next turned to plague the Thirteenth Doctor and Team TARDIS, eventually revealing the truth about the Timeless Child and building an army of CyberMasters from the remains of the Time Lords he had killed, becoming the host of the Cyberium consciousness to make himself their commander. However, his plot was thwarted when Ko Sharmus detonated the death particle on Gallifrey, wiping out whatever organic life remained on the planety, though the Master and his CyberMasters managed to escape to enact the Master's Dalek Plan, which saw the Master finally steal the Doctor's body and become the Doctor himself after posing as Grigori Rasputin. However, the Doctor was able to reclaim her body with help from her "extended fam", leaving the Master stuck back in his damaged body, though he was able to mortally wound the Doctor before he apparently expired.

Early life and exploits
There existed a variety of different and largely irreconcilable accounts of the Master's early life before the incarnation which became the Third Doctor's nemesis. These accounts differed on details including the physical appearances of the Master and the names they used during their early exploits.

The Master and a young Doctor became friends on their first day at the Time Lord Academy, (TV: World Enough and Time) and they shared many adventures (PROSE: Doctor Who and the Sea-Devils, The Eight Doctors, TV: The Time Monster, The End of Time, et al.) before falling out. (PROSE: Last of the Gaderene, TV: Death in Heaven)

After an illustrious political career, (PROSE: CIA File Extracts, Time and Relative, The Legacy of Gallifrey) the Master left Gallifrey and became a renegade on the same day or shortly after the Doctor left with Susan (COMIC: The Glorious Dead, PROSE: Celestial Intervention - A Gallifreyan Noir, AUDIO: The Toy) during a period of civil unrest. (PROSE: Birth of a Renegade)

By some accounts, the incarnation that left Gallifrey had brownish-grey hair and a short beard and already went by the name "Master". (AUDIO: The Destination Wars, The Home Guard, The Psychic Circus) According to other accounts, he hadn't yet chosen the name "the Master" and instead went by the name "Koschei". (PROSE: The Dark Path, The Face of the Enemy, Rebel Rebel) According to the Celestial Intervention Agency's research, he still hadn't chosen the name "Master" by his sixth incarnation, who called himself a "Monk"; (PROSE: CIA File Extracts) however, by most accounts, the Monk was a different childhood associate of the Doctor's. (PROSE: A Brief History of Time Lords, Divided Loyalties, No Future)

The Master's incarnations
The Master had the ability to control their regenerations, with each face selected bearing an imprint of their mind, leading the Master to keep the same characteristics across various regenerations. (PROSE: Harvest of Time)

After reaching the end of their original life cycle, the Master resorted to various expedients to extend their lifespan, including stealing or merging with the bodies of others, (TV: The Keeper of Traken, Doctor Who) creating incarnations who held themselves to be distinct from the base Thirteenth Master, (AUDIO: Masterful) but were not "exactly" new regenerations. (TV: The Five Doctors) By the time they reemerged after the Last Great Time War, the Master was once again in possession of a regeneration cycle, having been resurrected by the Time Lords, (TV: Utopia, The Sound of Drums) although other factors soon intervened to complicate their regenerative history. (AUDIO: The Lumiat, TV: The Power of the Doctor)

Before her encounter with, River Song believed that she had met all the Master's incarnations. (AUDIO: The Lifeboat and the Deathboat) Across multiple time streams, the Sild collected about 470 incarnations of the Master. (PROSE: Harvest of Time) Incidentally, the Master's old enemy, the Doctor, was known to have had hundreds of incarnations. (WC: The Secret of Novice Hame, PROSE: The Day of the Doctor)

Early life
Multiple contradictory sources discussed versions of the Master earlier than the one who began menacing the Third Doctor during his exile on Earth.
 * One account depicted the final falling-out, on Gallifrey, of the First Doctor with an ambitious Time Lord who had retained the nickname of "Magnus" from the same school days from which the Doctor was known as "Thete". (COMIC: Flashback) Though some accounts implied this "Magnus" to have been the Master, (PROSE: Goth Opera, etc.) others treated him as an incarnation of a distinct Magnus of whom the War Chief encountered by the Doctor during the War Games was also an incarnation. (PROSE: Divided Loyalties, etc.)
 * A Renegade Time Lord whom the First Doctor encountered in the 12th century in the guise of a monk (TV: The Time Meddler) and again during the Daleks' master plan (TV: The Daleks' Master Plan) was suggested by some accounts to be a version of the Master, predating his adoption of the moniker and a more aggressive approach to meddling in time; this was, at any rate, the Celestial Intervention Agency's belief at one stage. (PROSE: CIA File Extracts, A Sourcebook for Field Agents) However, most other accounts depicted the Monk as a Time Lord in their own right. (AUDIO: Too Many Masters, PROSE: Divided Loyalties)
 * One early incarnation of the Master was reckoned to be the "third or fourth" by the Fourth Doctor. (AUDIO: Blood of the Time Lords) He first met the First Doctor on the planet Destination while living under the alias of "the Inventor", but was already using the name of "the Master". (AUDIO: The Destination Wars) By the time of an encounter with the Second Doctor, he was beginning to lay the groundwork for a grand plan involving taking Earth soldiers out of time. (AUDIO: The Home Guard)
 * After another version of him regenerated in a Trastevarian jail, (PROSE: Save Yourself) a renegade Time Lord who had once known the First Doctor began to act as the War Chief of an alien War Lord. (TV: The War Games) Multiple accounts suggested he was an incarnation of the same man who later became "the Master", (AUDIO: The Home Guard, PROSE: Doctor Who and the Doomsday Weapon, etc.) although others claimed that "the War Chief", or Magnus, was a distinct Time Lord. (PROSE: Divided Loyalties, A Brief History of Time Lords, GAME: The Legions of Death)

UNIT onwards

 * An incarnation of the Master accumulated a large number of schemes to take over the Earth during the period when the Third Doctor was exiled on Earth, (TV: Terror of the Autons, The Dæmons, etc.) and later allied with the Dalek Empire as part of the Second Dalek War. (TV: Frontier in Space) Multiple accounts of his ultimate fate existed. (PROSE: Legacy of the Daleks, COMIC: Doorway to Hell, etc.)
 * The Decayed Master was a decrepit, skeletal version of the Master who, having reached the end of his natural life cycle, engaged in multiple schemes to acquire more regenerations and/or steal healthier bodies. (TV: The Deadly Assassin, The Keeper of Traken) He successfully merged with Traken's Consul Tremas, transitioning to a healthier form, (TV: The Keeper of Traken) but some accounts showed that the Master was later reverted to his decaying form on multiple occasions before he managed to rid himself of it permanently. (AUDIO: Dust Breeding, Mastermind, Planet of Dust)
 * After merging with Tremas, the Master lived on in a more youthful form who was responsible for the Fourth Doctor's death at the Pharos Lighthouse, (TV: Logopolis) and subsequently menaced the Fifth Doctor, Sixth Doctor and Seventh Doctor. (TV: Castrovalva, The Mark of the Rani, Survival) Multiple accounts of his ultimate fate existed; (PROSE: First Frontier, The Eight Doctors, AUDIO: Dust Breeding) two unrelated ones suggested that before the end, he had managed to convert his body from a Trakenite into a biologically Gallifreyan one. (PROSE: The Velvet Dark, First Frontier)
 * An "old Master" was put on trial by the Daleks on Skaro. Despite their different appearances, (TV: Doctor Who) one account suggested this was still the "Tremas" Master, (PROSE: The Eight Doctors) but others concurred that he was a renewed version of the Master, having managed to regenerate using the technology of the Tzun. (PROSE: The Novel of the Film, First Frontier) This body was blown apart when the Daleks executed him, forcing the Master to resort to possession once again. (TV: Doctor Who)
 * After surviving in the form of a Deathworm Morphant, the Master stole the body of a paramedic named Bruce. The new Master initiated a plan to use the Eye of Harmony to steal the Eighth Doctor's remaining lives, but instead fell into the Eye of Harmony. (TV: Doctor Who) He escaped from it on multiple occasions, but tended to end up tossed back into the Time Vortex. (AUDIO: The Lifeboat and the Deathboat, etc.) His body eventually began to destabilise, becoming phantom-like and warped, and when he was resurrected by the Glory, he was transferred into a new body, that of of an American street preacher. (COMIC: The Glorious Dead)
 * Resurrected into the body of a black American preacher, (COMIC: The Fallen) the Master tried to take control of the Omniverse through the Glory, battling the Eighth Doctor once again, but was ultimately banished to parts unknown by Kroton. (COMIC: The Glorious Dead) When he ultimately emerged from the Eye of Harmony for good, the Master appeared as a gas and took possession of a series of human bodies, though found they all eventually decayed to resemble his original decayed form. (AUDIO: Mastermind) In his decayed form he was finally killed by the Ravenous, (AUDIO: Planet of Dust) though was resurrected by his past and future selves who made a deal with the Celestial Intervention Agency to give him a new regeneration cycle. (AUDIO: Day of the Master)

Time War onwards

 * After his resurrection, (AUDIO: Day of the Master, etc.) the "Reborn" Master was an arrogant, conspicuously bald man who once spent some time posing as the Doctor. (AUDIO: Dominion)
 * The War Master participated in the Last Great Time War, (AUDIO: Beneath the Viscoid) but, terrified when he saw the Dalek Emperor taking control of the Cruciform, ran to the end of the universe and made his body human, (TV: The Sound of Drums) with the kindly Professor Yana remaining safe until after the War. When the Tenth Doctor stumbled upon him, Martha Jones accidentally spurred Yana to release the Master's consciousness from the fob watch. However, the returned War Master only lived briefly before being fatally shot by Yana's assistant Chantho, regenerating into a new form. (TV: Utopia)
 * During the Time War, the Master regenerated into the form of a young child who brokered an uneasy alliance with the War Doctor, (COMIC: The Then and the Now) but this regeneration was ultimately averted by a time paradox, with the Master being reverted to his older, War Master form. (COMIC: Fast Asleep)
 * In a younger body, the Master became Prime Minister of the United Kingdom under the name of Harold Saxon and successfully took over the Earth during "the Year That Never Was", but was ultimately defeated and shot by his human consort. (TV: The Sound of Drums, Last of the Time Lords) He had, however, arranged for his resurrection, (TV: The End of Time) and would ultimately die at the hands of his future self. (TV: The Doctor Falls)
 * Having regenerated into a female body, the Master adopted the nickname of Missy. She arranged for the Eleventh Doctor to meet Clara Oswald (TV: The Bells of Saint John, Death in Heaven) and created the Nethersphere. The Twelfth Doctor's discovery of this artificial afterlife was the first of many encounters between him and Missy, (TV: Dark Water, The Magician's Apprentice, etc.) and they had even tried to renew their friendship, with Missy pledging to renounce her "evil" ways, by the time the two were killed on a Mondasian colony ship, with Missy being shot in the back by her own past self. (TV: The Doctor Falls)
 * Because the laser bolt her past self had shot her with disabled regeneration, (TV: The Doctor Falls) Missy had no choice to survive but to enact the Elysian field. This created the Lumiat, a manifestation of the Master with a reset regeneration cycle, who intended to put Missy's noble intentions into practice and become a force for good. Encountering an earlier version of Missy, however, the Lumiat was shot and began to regenerate, with Missy hoping that this would spur the next one along to abandon these moral ideals. (AUDIO: The Lumiat)
 * The Thirteenth Doctor next encountered a Master who referred to himself as a "Spy" Master. His worldview having been toppled by the discovery of the Timeless Child, this Master razed Gallifrey and acted as an enemy to the Doctor again. (TV: Spyfall, The Timeless Children) After gaining powers of foresight by merging with the Cyberium, the Master hatched a final scheme to usurp the Doctor's entire existence via a forced regeneration, but was forced back into his original body by Yasmin Khan and the Holo-Doctor. By then, this original body was failing due to the stress he had put it through, and he only found the strength to kill the Thirteenth Doctor in turn before he collapsed, seemingly dead. (TV: The Power of the Doctor)

Undated events

 * At some point, a version of the Master pursued some sort of scheme in mid-20th century Chicago, which involved wiping out a biker gang. His plot was foiled by the Celestial Intervention Agency member Rollo with the help of a surviving gangster, Jim Waters, whom Rollo ended up taking on as a companion. (GAME: )
 * A version of the Master posed as Merlin in Camelot, facing the Fifth Doctor, (COMIC: The Creation of Camelot) and had two subsequent encounters with the Sixth Doctor. (PROSE: The Fellowship of Quan, The Radio Waves)
 * One of the incarnations of the Master who were extracted from their time streams and imprisoned by the Sild was encountered by the Third Doctor as a masked woman wearing a frilly black dress. She had black hair streaked with white, combed back from her forehead. The Doctor noted "a familiarity" in the shape of her cheekbones and brow, in accordance with the Master's ability to control their regeneration finely and maintain an air of familiarity from one body to the next. (PROSE: Harvest of Time)
 * At some point before his exploits on Destination, the Master claimed to have met Harry Houdini. (AUDIO: The Destination Wars)
 * The Master travelled with Finsey, a woman who was fascinated by his evilness, until he saw no further use for her and tried to have her killed. (AUDIO: The Transcendence of Ephros)
 * An unknown incarnation of the Doctor failed to prevent the Master from escaping. He tried to take off after him, but the Master had sabotaged the Doctor's TARDIS, forcing him to play a quiz game before he could start the engines again, and thus successfully delaying him. The Master, calling the Doctor "my dear fellow", mocked him over the TARDIS speakers as he took off. (PROSE: Enjoy the Game)
 * One incarnation of the Master confronted a version of the Ninth Doctor on Tersurus (TV: The Curse of Fatal Death), spending many years crawling through the sewers there (TV: The Curse of Fatal Death, AUDIO: The Bekdel Test) due to a trick of the Doctor's. He then teamed up with the Daleks, and witnessed several of the Doctor's subsequent regenerations. Thinking the Doctor dead, he, along with the Daleks, renounced evil in memory of the Doctor, who then regenerated into a female incarnation, whom the Master fell in love with. (TV: The Curse of Fatal Death)
 * During the Time War a version of the Master was captured by the Union who tested her degeneration weapon on them, (AUDIO: The Union) causing them to shift between their bodies. In an attempt to stabilise, they accidentally went too far forward in their life and became Missy even though she was in their future. Stable for a time, Missy occupied herself trying to recreate The War of the Worlds on Planetoid 50, creating a facsimile of Victorian London and populating it with kidnapped residents, including the Paternoster Gang, and created fake Martians to invade, however she lost control of them. The Doctor arrived in the midst of their own degeneration crisis, and Missy helped stabilise them as the Tenth Doctor. After the Doctor dealt with the fake Martians by shrinking them, Missy began to destabilise again and left to degenerate alone. (AUDIO: The Martian Invasion of Planetoid 50) The Master subsequently became the Lumiat and travelled to a beach on Solaris Hexis where they met Liv Chenka. The pair were transported to the Hall of the Time Lord Immemorial where they encountered the degenerating Doctor, now in the form of the Ninth Doctor, and a version of the Doctor from another universe. The Lumiat helped fulfill the prophecy to summon the Time Lord Immemorial to prevent the universes colliding, serving as both the Doctor’s greatest friend and foe. She subsequently returned Liv to the beach whilst trying to hold off another degeneration, and rapidly departed before she changed as she knew Liv would not like her other selves. (AUDIO: Time Lord Immemorial) After the Union’s weapon was destroyed and the degeneration energy dispersed, the Doctor believed the Master would return to normal. (AUDIO: The Union)

Other realities
Many versions of the Master were unique to various alternative realities.

Possible futures
Whilst exposed, the heart of the Master's TARDIS showed him some of his possible futures. In one the Master was horribly deformed, being cared for in a Zero Room on Gallifrey after being rescued by Chancellor Goth. In another, however, the Master achieved his aim of conquest, but now possessed an entirely alien body. (AUDIO: The Threshold)

A "listless-looking" Ninth Doctor who existed as a separate future for the Eighth Doctor from the "man with big ears" (PROSE: The Tomorrow Windows) was the contemporary of a male incarnation of the Master with a black beard and wild hair, who wore an outfit with a long cloak and a large green collar. (TV: The Curse of Fatal Death)

Alternatively, an pale, aristocratic Ninth Doctor (PROSE: The Tomorrow Windows) was accompanied in the TARDIS by a bearded Master who now resided in an android body. (WC: Scream of the Shalka)

In an aborted timeline, the gathered incarnations of the Master were faced with an entropy wave that threatened to destroy and consume the universe. However, the War Master eventually deduced the wave was actually their final form. (AUDIO: Masterful)

Parallel universes
According to one group of human historians, Morgaine was the equivalent of the Master in Arthur's World, an alternative reality ruled by magic instead of science where the Time Lords were the "Magic Lords". Her enemy was Merlin, himself the counterpart of the Doctor, who became part of King Arthur's court after being exiled to Earth. The Thirteenth Doctor published the work of these historians but did not directly comment on their reading of the Merlin Doctor; in her introduction, she merely noted some ideas in the book were clever while others were "a bit daft". (PROSE: The Monster Vault)

In one of the infinite parallel universes of "possible space", (COMIC: Fire and Brimstone) the Master was the grandson and heir of Barusa. He was believed to be Barusa's only living descendant, but Barusa actually had another grandson, the Master's greatest rival and — secretly — his half-brother: the Doctor. (PROSE: The Chronicles of Doctor Who?)

On the Inferno Earth, the Master was still a loyal Time Lord who went under the name Koschei. He was working for the Celestial Intervention Agency and travelled with a human companion called Ailla. They became stranded on Earth after defeating the Great Intelligence, and the Republic of Great Britain captured him for information. Ailla was killed and Koschei was tortured until all his regenerations were used up. Koschei died when he was confronted by the Master from N-Space, who turned off his life-support machine at his request. (PROSE: The Face of the Enemy)

In the Unbound Universe, a reality where the Doctor did not arrive on Earth until 1997, the Master had become stranded on the planet following his TARDIS being placed "beyond [his] reach". Initially finding work with the United Nations, the Master defected to China following the failure of the World Peace Conference, trying to cause enough chaos to attract the Doctor's attention. Using alien parasites to build more Keller Machines, the Master brainwashed political prisoners, making them mindless soldiers, later to be organised in the infamous Ke Le Divisions. In 1997, when the new Chinese government lost faith in him, the Master tried to escape to Hong Kong, hoping to claim the last of the parasites only to regenerate into a new incarnation after his plane crashed. Though the Master claimed the parasite, he abandoned the scheme to strike a deal for passage offworld with the recently arrived Doctor. When the Master reneged on the deal, he found himself outgambitted by the Doctor and left on Earth. (AUDIO: Sympathy for the Devil) Evenetually managing to escape Earth, the Master became a key player in the Great War, working with the Doctor until he deemed the Master's plans too insane. After the War, the Master attempted to escape the dying universe by tricking people into entering his portal at the Emporium, which instead killed them to power up a true portal for him. His scheme was exposed by Bernice Summerfield and the Doctor. (AUDIO: The Emporium at the End) He resurfaced when the Doctor was being impeached as President of the Universe. He succeeded the Doctor by promising to activate the Apocalypse Clock to create a safe zone regardless of the potential consequences. This briefly unleashed the Great Old Ones, but the Doctor stole their energy to transport Bernice home. This left the Master with all the responsibility of ruling the universe and with the Parliament to constrain him. (AUDIO: The True Saviour of the Universe) After his universe finally came to an end, the Master was the last being left alive inside a shielded bubble, a fate he was saved from by the Dalek Time Strategist who recruited him for aid in thwarting his N-Space's counterpart perversion of Dalek history. (AUDIO: Shockwave) When the scheme was thwarted and the Daleks restored, the Master fled through a wormhole into the larger multiverse. (AUDIO: He Who Wins)

In an alternative universe created by the Quantum Archangel, the Master joined the Time Lords to fight in the War. However, he began aiding the Daleks by giving them temporal manipulation technology. The Sixth Doctor, who was Lord President Admiral of Gallifrey, activated the Armageddon Sapphire and destroyed the universe rather than letting the Enemy win. (PROSE: The Quantum Archangel)

In a different alternative universe created by the Archangel, the Master cooperated alongside the Rani, the Monk and Drax to try to destroy the world using a DNA recombinator, turning the human race into a gestalt consciousness which could be used as a weapon to conquer the universe. (PROSE: The Quantum Archangel)

In a parallel universe, the Master used many fake names, including Roger, Peter, Geoffrey, Tony, Eric, Robert and Sam. That universe's version of the Doctor mistook Bob for the Master and used Venusian aikido on him. (AUDIO: Exile)

In a parallel universe, the Master was inside his TARDIS when it was parked on Earth in 1981. The Doctor's TARDIS materialized around it. (TV: Logopolis) This was part of the events that would lead to Logopolis' destruction and the Fourth Doctor's regeneration. (TV: Logopolis, AUDIO: He Jests at Scars...) When the Valeyard was fixing his past mistakes, he tried to stop his younger self's trip to Logopolis in order to save the planet. But he accidently time-rammed his younger self and past TARDIS, destroying them. The Master's TARDIS was time-rammed too as it was inside the Doctor's TARDIS. (AUDIO: He Jests at Scars...)

In the Warrior's universe, an incarnation of the Master fought with the Warrior in an alternate version of the Last Great Time War. He guided the Warrior into sealing off a timeline where the Unified Skaroan Alliance won the Time War into a Carrisent Particum. (AUDIO: Aftershocks)

Saxon's multi-Master event
In another aborted timeline, the mortally wounded "Saxon" Master sought to survive his death and avert becoming Missy. He travelled to the human colony on Kiameth, taking it over and using the energy of the planet to thrive and flourish, so that he could heal his own decaying body. Though the colony flourished for a time, he had unleashed a sentient entropy wave, which the "War" Master later deduced was actually the final form of the Master, that destroyed Kiameth. The wave then spread across the universe, despite the efforts of a parallel Master to combat it by throwing the resources of the Time Lords and Daleks at it. In the ruins of Kiameth, the "Saxon" Master used a time scoop to take six of his previous selves out of time (the young Master before leaving Gallifrey, the "Decayed" Master, the "Tremas" Master who sent Kamelion in his stead, the "Bruce" Master, the "Bald" Master and the "War" Master) and brought them to his castle, intending to use the Attornium to take their lives in a desperate bid to survive.

His attempt to time scoop the "UNIT enemy" Master failed, with Jo Grant being caught instead. The Masters decided to sacrifice her for fun, but were interrupted by Missy. She exposed the "Saxon" Master's plan and used the time scoop to scatter the different incarnations along the timeline of Kiameth, to see if any of them would find a chance of redemption by either stopping the wave or salvaging something from its aftermath. Missy herself explored the ruins of Kiameth, after loaning her space yacht to the parallel Master, along with Jo. During their explorations they were pursued by the entropy creature and contacted by the Lumiat, who tried to warn them about what the Master had done. The entropy wave caught Jo and Missy reunited with the parallel Master, who conceded defeat and returned to his own universe. Only four of the Masters managed to do as Missy has hoped: the "Decayed", the "Bald", the "War" and Missy herself. The others, who had turned against Missy, were killed by Kamelion on Missy's orders, though the "Saxon" Master escaped. Despairing about her future, Missy convinced the surviving Masters to use "Saxon's" Attornium to stop the creature by feeding on it, but the "War" Master refused to allow it as the plan would cause a massive energy release capable of destroying any universe. He discreetly poisoned himself and every other incarnation of the Master, having realised the wave was their own future, then turned off the Attornium and left Missy to be devoured by the wave. The resulting paradox erased the events of this timeline, bringing the universe back to normal. (AUDIO: Masterful)

Other
In an alternate timeline where the Cybermen allied with Rassilon to take over history, (COMIC: Supremacy of the Cybermen) the Master, while fighting the Third Doctor, was caught up in a time distortion which resulted in him being cyber-converted while pleading to the Doctor for help. (COMIC: Prologue: the Third Doctor)

Discovering that the Celestial Intervention Agency were gathering illegal Vess weapons, the Decayed Master blackmailed their agent, Straxus, into handing over a conceptual bomb. The Master then visited Bob Dovie and, after killing his family, planted the device into his head. When Dovie saw the inside of the Doctor's TARDIS, his refusal to believe in it caused the Doctor's TARDIS to explode, causing its timeline to begin to collapse. With the Doctor's timeline collapsing along with the TARDIS's, the Doctor's first eight incarnations joined forces to avert the detonation of the bomb, before the First Doctor erased the events from history. (AUDIO: The Light at the End)

Personality
The Master was the polar opposite of the Doctor in almost every respect; condescending, arrogant, vain, and lusting for power. (TV: Terror of the Autons, Colony in Space, The Sound of Drums) However, the Master's insanity was in part due to the High Council from Gallifrey's future sending a four-beat rhythm of drums into the Master's mind, (TV: The End of Time) with the Tenth Doctor recalling that staring into the Untempered Schism as a child had been "how it all started" for the Master. (TV: The Sound of Drums)

Comfortable with their villainous reputation, the Master took insults about their wickedness as compliments, (TV: The Time Monster, The Five Doctors, Doctor Who, The Sound of Drums) and reacted with offence if someone asked them if they had turned over a new leaf, (TV: The Magician's Apprentice) to the point that they refused to even acknowledge the Doctor's attempts to change them. (TV: The Doctor Falls)

When introducing himself, or enthralling someone, the Master would usually say, "I am the Master, and you will obey me." (TV: Planet of Fire) He also liked to say "my dear Doctor" when addressing his adversary. (TV: Colony in Space, The Sea Devils, Time-Flight, The Caves of Androzani, The Doctor Falls)

Unlike the Doctor, who usually needed their companions to convince people that they knew what they were doing, the Master had no problem manipulating people into helping him with his evil plans, (TV: The Time Monster, Doctor Who) even getting people to side with by exaggerating certain truths about the Doctor to paint him in a bad light. (TV: The Lazarus Experiment; COMIC: Doorway to Hell)

Extremely self-centred, the Master was willing to destroy Gallifrey to regenerate himself, (TV: The Deadly Assassin) believed that the battle for the Glory was to be between him and the Eighth Doctor, (COMIC: The Glorious Dead) thought that Carmen's prophecy referred exclusively to him, (TV: The End of Time) and viewed the Doctor's saving Gallifrey as an attempt to save her. (TV: Death in Heaven) So great was the Master's ego that he was unable to work with his other incarnations, with the "UNIT enemy" incarnation being psychically attacked by his other selves when he took control of the Sild's telepathic network, (PROSE: Harvest of Time) and the Seventh Doctor defeating the "Decayed" and "Reborn" Masters by tricking them into arguing with themselves over ownership of the universe. (AUDIO: The Two Masters) Though the "Saxon" Master and Missy worked more amicably, their clashing views on helping the Twelfth Doctor eventually led them to killing each other out of spite, with Missy purposefully forcing her past incarnation's regeneration to ensure that he would become her and stand with the Doctor. (TV: The Doctor Falls) In the aborted timeline in which "Saxon" tried to avoid his regeneration into Missy, he planned to feed on the life force of five past incarnations and came into direct conflict with Missy herself, who exposed his schemes and manipulated the Masters to her own ends. Three incarnations eventually joined the "Saxon" Master in working against her, so she had them killed. (AUDIO: Masterful) When Missy came into contact with her future self, the Lumiat, she similarly clashed with her, though over a difference in morality rather than ambition. The Lumiat eventually lost her patience with her past self and attempted to shoot her with a TCE, though Missy manipulated the situation to enable her to shoot the Lumiat instead. (AUDIO: The Lumiat)

The Master's schemes usually fell into three categories; conquest, (TV: Terror of the Autons, The Mind of Evil, Colony in Space, The Dæmons, The Time Monster, Logopolis, The Sound of Drums) survival, (TV: The Deadly Assassin, The Keeper of Traken, The Five Doctors, Planet of Fire, Survival, Doctor Who, The End of Time) and the death of the Doctor. (TV: Castrovalva, The Ultimate Foe) Similar to the Monk, the Master would also, on occasion, attempt to disturb the flow of history, (TV: The King's Demons, The Mark of the Rani) and, when imprisoned, would devote their energies to gaining their freedom. (TV: The Claws of Axos, The Sea Devils, Time-Flight, Utopia, The Doctor Falls)

Throughout their lives, the Master would adopt many disguises and aliases, often to pursue their goals, (TV: Terror of the Autons, The Mind of Evil, Colony in Space, The Dæmons, The Time Monster, Frontier in Space, Castrovalva, The Sound of Drums, Spyfall) though other times with no reason or explanation given. (TV: Time-Flight, The Mark of the Rani)

The Master's disguises ranged from the providence of false qualifications, (TV: Terror of the Autons, The Mind of Evil, Colony in Space, The Dæmons, The Time Monster, Frontier in Space, The Sound of Drums) to employing masks and heavy makeup (TV: Terror of the Autons, The Mind of Evil, The Claws of Axos, Castrovalva, Time-Flight, The King's Demons, World Enough and Time) or a change of clothing, (TV: The Sea Devils, Logopolis, The Mark of the Rani, Spyfall) to even changing physical forms. (TV: The Keeper of Traken, Utopia, Dark Water, Spyfall)

In a show of vanity, the Master's choice of alias would often reflect their title of "Master". (TV: Terror of the Autons, The Dæmons, The Time Monster, The King's Demons, The Sound of Drums, Dark Water; PROSE: Doctor Who Fights Masterplan "Q", Night Flight to Nowhere, The Time Savers, Legacy of the Daleks, Last of the Gaderene, The Quantum Archangel, The Duke of Dominoes, The Spear of Destiny, Yes, Missy; AUDIO: Dust Breeding, Trail of the White Worm, Mastermind, The Evil One, And You Will Obey Me, Masterpiece, The Two Masters, The Coney Island Chameleon)

Before their first battle, the Third Doctor called the Master a "jackanapes" and an "unimaginative plodder", (TV: Terror of the Autons) but later came to view him as the "personification of evil". (TV: The Sea Devils) The Fourth Doctor described the Master as both the "quintessence of evil", (TV: The Deadly Assassin) and a "vengeance fixated sociopath with megalomaniacal tendencies". (AUDIO: Trail of the White Worm)

However, the Seventh Doctor recognised the Master as an "evil genius", (TV: Survival) with the Tenth Doctor sincerely calling him "stone-cold brilliant". (TV: The End of Time) The Twelfth Doctor once stated that Missy was the only person "as smart as [him]". (TV: The Lie of the Land)

High Council President described the Master as "one of the most evil and corrupt beings [the] Time Lord race [had] ever produced" and that his "crimes [were] without number, and [his] villainy without end." (TV: The Five Doctors) Rassilon described the Master as the Time Lords' "most infamous child". (TV: The End of Time)

Iris Wildthyme called the Master a "phallocentric dope", (PROSE: The Scarlet Empress) while Ashildr described Missy as the "lover of chaos". (TV: Hell Bent)

Relationship with the Doctor
The Master's relationship with the Doctor was complex. (TV: The Magician's Apprentice) They respected the Doctor as a worthy opponent, once offering to use a recently recovered weapon to take control of the universe while offering to share it with the Doctor though he refused. (TV: Colony in Space) As time went on, however, the Master became increasingly obsessed with proving his personal superiority, causing him to view the Doctor both as his greatest friend and his worst enemy. He expressed deep anger toward the Doctor, along with a desire for vengeance, (TV: Last of the Time Lords) and accused the Doctor of causing him to waste his regenerations. (TV: Doctor Who)

Although initially willing to work with the Doctor when the situation required it, (TV: Terror of the Autons, The Claws of Axos) after the Last Great Time War, the Master absolutely refused to listen to the Doctor on any occasion. He evinced his vanity when the Doctor confronted him with the words "I forgive you", which he had been terrified of hearing because it significantly dented his pride. (TV: Last of the Time Lords)

The Master enjoyed making playful flirtations towards the Tenth Doctor while speaking on the phone, even asking the Doctor if he was asking him out on a date. (TV: The Sound of Drums) When the Doctor harnessed the psychic energy of the entire human race and effectively became a god, the Master was reduced to sobbing against a wall. (TV: Last of the Time Lords)

After regenerating into a female incarnation, Missy took her sexual innuendos to a new level by referring to him as her "boyfriend" and holding him responsible for her fate. (TV: Deep Breath,  Death in Heaven) Upon meeting the Twelfth Doctor, she pretended to be an android and passionately kissed him. (TV: Dark Water) She later wanted to give him control of her army of Cybermen, attempting to force him to recognise that they were the same, but he refused and gave it to Danny Pink instead, who stopped her plans. While surprised, Missy didn't try to stop the Doctor as he prepared to kill her to spare Clara Oswald from doing it. (TV: Death in Heaven) When searching for the Doctor, Missy challenged Clara's skepticism about her concern about him by claiming to have cared about the Doctor "since always" (TV: The Magician's Apprentice) and even begged the Doctor to find out about her plans. (COMIC: The Five Masters) Shortly before her encounter with her predecessor, Missy showed a genuine desire to rekindle her friendship with the Doctor. (TV: The Eaters of Light) In fact, she had been rehabilitated enough that she would stand with him to fight the Cybermen. (TV: The Doctor Falls)

Missy's male successor enjoyed playing long games, like tricking the Doctor into believing he was someone else, expressing he had had "a lot of fun" when the Thirteenth Doctor finally realised he had fooled her. Despite not wanting her as his enemy again, he loved playing mind games on the Doctor and treating her as an inferior, having her kneel and call him "Master". He chased her through time to force her to listen to him just to get a message across, but would express rage when she outsmarted him. (TV: Spyfall)

Companions
Unlike the Doctor, the Master usually worked and travelled alone. On rare occasions, they were seen with companions. Examples included Ailla the Time Lord spy; (PROSE: The Dark Path) Mother Finsey, a woman who was fascinated by the Master's evilness and would follow his track afterwards; (AUDIO: The Transcendence of Ephros) Chang Lee, a young human whom the Master met in San Francisco; (TV: Doctor Who) Katsura Sato, an immortal Japanese samurai who helped the Master in his quest for Glory; (COMIC: The Glorious Dead) and Sally Armstrong, a woman who helped him to use the Eminence. (AUDIO: Time's Horizon)

During the Last Great Time War, he took in Cole Jarnish, (AUDIO: The Good Master) though as a ploy, (AUDIO: The Heavenly Paradigm) and later Chantho, a female assistant and companion to the Master in his "Professor Yana" identity. (TV: Utopia) As Harold Saxon, Lucy Saxon, his wife, was described as having travelled with the Master in the TARDIS in the same fashion as the Doctor and his companions. (TV: The Sound of Drums)

Clara also temporarily became Missy's companion when they both teleported out of the Dalek city together. Missy treated Clara as her "canary", forcing her to act as bait for the Daleks and test the safety of their situations first. She also made her get inside a Dalek casing so they could sneak back into the city convincingly. (TV: The Witch's Familiar)

Character conception and development
Barry Letts and Terrance Dicks often discussed that the relationship between the Third Doctor and the Brigadier was similar to Sherlock Holmes and Dr Watson, and envisioned a counterpart of the Doctor to act as "Moriarty", a character that became "the Master", his name being developed to counter the Doctor's — like that of his enemy, "Master" is an academic title. (DOC: The Doctor's Moriarty)

In the Third Doctor's original final episode concept, Roger Delgado's incarnation of the Master would have redeemed himself and given his life to save the Doctor, after which the Doctor would have regenerated; however, this story was never developed due to the sudden death of Roger Delgado. Over thirty years later, this idea was reused in The End of Time, with John Simm's incarnation of the Master seemingly sacrificing himself to save the Tenth Doctor from Rassilon (although The Doctor Falls later revealed that his incarnation of the Master had survived this event).

In The Deadly Assassin, writer Robert Holmes deliberately chose to show the Master in a "transitional" form, in case future production teams wanted to bring back the character. As reported by Doctor Who Weekly #5, the intent at the time was that the Master had succeeded in gaining new regenerations and was beginning to regenerate in the scene where he escapes Gallifrey in Goth's TARDIS; it was expected that when the Master next returned, it would be in a once-more-healthy, new body. However, this idea was not included in the novelisation; as the Target novelisations were informally used by John Nathan-Turner as continuity guides, over the original scripts, this resulted in the decayed Master reappearing in The Keeper of Traken (albeit looking slightly healthier).

The relationship between the Doctor and the Master has often been thought of by fans as a romantic, or formerly romantic, one. This has only sparsely been hinted at in official media, although David A. McIntee reported that he once pitched a Virgin Missing Adventure novel which would have featured the Fifth Doctor and, and, in a subplot, revealed the Doctor and the Master as ex-spouses.

Near uses
The Master was the villain in the early drafts of the 1977 television story The Talons of Weng-Chiang, until he was replaced by Magnus Greel.

When writing the 2015 audio story The Black Hole, Simon Guerrier intended for Constable Pavo of the Time Lord police force to be an earlier incarnation of the Master. This is strongly hinted at in the story, where Pavo makes use of a deadly "silver baton", possesses hypnotism similar to the Roger Delgado Master's, and seems to be on the path to breaking away from Gallifrey's authority, as she ends up wiping the Doctor and companions' memories of their encounter and letting them go so as not to risk implicating herself concerning her own transgressions. However, the connection is not spelled out.

The mystery of the Master's true name
The 1997 novel The Dark Path shows the Second Doctor in what is purported to be his first encounter with the Master since leaving Gallifrey. Throughout the story, the Master is only called by the name "Koschei", and it is only at the end of the tale, when his turn to evil is complete (as foreshadowed by the title), that he proclaims himself "the Master". In Russian folklore, Koschei (rus. or Коще́й Бессме́ртный, "Koschei the Deathless") is a villainous sorcerer who hid his soul in an obscure location under many layers of protection so that he may never die. The Face of the Enemy, by the same writer, saw Roger Delgado's Master encountering a parallel version of himself for whom The Dark Path had not happened, who still called himself "Koschei". The Second Doctor recognises Koschei's name in The Dark Path when Ailla mentions it, although the narration also suggests that it is an alias rather than the Master's birth name. Writer David McIntee commented on his Tumblr blog: "The intention is certainly that (a bit like Anakin Skywalker) it’s a name he never uses later - but being set before he’s called the Master means he has to be called *something*. As for whether it’s actually his original real name… Well, in my head, yeah, but you’ll notice (IIRC) that the Doctor doesn’t address him by that name until after it’s been mentioned by others, so it not necessarily the case."

- David McIntee

In Divided Loyalties, flashbacks to the Doctor's childhood in "the Deca" have the future Master already calling himself "Koschei" at the Time Lord Academy, although it is no clear if this is his birth name or a school nickname like "Theta Sigma" (the name persistently used for the Doctor in those same flashbacks). Although the flashbacks themselves come in the form of dreams the Doctor has under the influence of the Celestial Toymaker, and are explicitly inaccurate in some respects, the epilogue confirms that "Koschei" eventually became obsessed with "becoming the Doctor's Master".

The comic Flashback was written with the intent that Magnus, an old friend of Theta Sigma who seems to be growing more and more corrupted, was an early incarnation of the Master. However, the comic did not explicitly confirm Magnus's identity, and later sources went on to use "Magnus" as a name for the War Chief, although the Master and War Chief are sometimes thought to be one and the same. Interestingly, in the original script, the name was not "Magnus" but "Magus", the Latin word for "sorcerer" or "wise man"; it was incorrectly "fixed" to Magnus by the letterer, who assumed Magus was a typo.

The Black Hole featured the Second Doctor bumping into a Time Lord called Pavo, working for the Time Lord police to track down renegades (consistent with the claim in Time and Relative that the Master was a "truant officer" who was originally sent by the Time Lords on the Doctor's trail before deciding to become a Renegade himself). This Time Lord was intended by writer Simon Guerrier to be the Master prior to their turning evil; there are other clues to Pavo's identity, such as the silver rod Pavo wields as a weapon or their hypnotic abilities. It is, in any event, not made clear whether "Pavo" is an alias, nickname, code name, or birth name.

Beyond all those possibilities, several accounts suggest the Master's true name was something altogether more alien than "Koschei," "Magnus," "Magus" or "Pavo". In Doctor Who and the Terror of the Autons, Adelphi speaks the Master's birth name to the Doctor when warning him about the Master's arrival on Earth (the suggestion being that he has only recently adopted the pseudonym of "the Master", which Adelphi believes the Doctor might be unfamiliar with). It is described "a string of mellifluous syllables — one of the strange Time Lord names that are never disclosed to outsiders". This was eched by the 2018 short story Lords and Masters, which had Missy stating that her real name contained thirty-two letters. However, this does not foreclose the possibility that though any one of the spelled-out, shorter names given in other sources might be nicknames, they could be formed by shortening the Master's true name, similar to Romanadvoratrelundar usually going by "Romana".

How many Masters?
Especially in comparison to other prominent Time Lords like the Doctor and Romana, the number of the Master's incarnations has been left unclear by many stories. TV: The Deadly Assassin gives the first clue when the Master is said to be near the end of his thirteenth and final incarnation. PROSE: Legacy of the Daleks shows the transformation from the Roger Delgado Master into the degraded form portrayed by Peter Pratt in The Deadly Assassin, establishing that they, and Geoffrey Beevers, are playing a single regeneration of the Master. However, the comic Doorway to Hell contradicts this by showing the Delgado incarnation's regeneration, and AUDIO: The Two Masters features the Beevers incarnation of the Master before disfigurement.

The lack of ordinal numbers has prompted many conflicting naming schemes for each incarnation of the Master:

Evidence in invalid entries
The Doctor Who Role Playing Game by FASA, which admits to taking liberties with the source material in its opening pages, gives a rundown of the Master's first thirteen incarnations in "The Master" supplement book, which was similar to (but not entirely consistent with) the in-universe biography given for the Master in FASA's own CIA File Extracts.

According to the book, the Master could control the form of his incarnations, and frequently used the same face. His first to fourth incarnations lived on Gallifrey and regenerated due to his researches. The Fifth Master kept the same face as his predecessors, but lasted over four-hundred-years due to his retirement. He eventually regenerated, aged over 700-years-old, when his rebellion on Gallifrey failed and forced him to become a renegade, with the War Chief among his followers. The sixth and seventh incarnations were "the Monk", as portrayed by Peter Butterworth, being different from his previous incarnations mostly by lacking a beard, who regenerated when repairing his TARDIS after the events of The Time Meddler. The Eighth Master, aged over 800-years-old, regenerated following the events of The Daleks' Master Plan, returning to a bearded Delgado-like appearance and being the first to call himself "the Master". He kept these features up to his twelfth incarnation which combed his grey hair back. The thirteenth incarnation, still aged over 800-years-old, started intervening against UNIT, but, after his death to the Daleks following Frontier in Space, took on the decayed appearance of Peter Pratt. The Fourteenth Master, aged over 900-years-old, was portrayed by Ainley, who stole the body of Tremas and he survived the events of Planet of Fire, due to the gas which gave him a new cycle and he regenerated into a similar fifteenth incarnation.

The 2010 edition of The Visual Dictionary indicates that the Master played by John Simm is the seventeenth incarnation. However, this source is considered invalid by this wiki for being non-narrative.

Valid entries
The short story Girl Power! showed eighteen deaths on Missy's Spacebook page. This results in nineteen true incarnations to result from regeneration, not including incarnations who come into being as possessed bodies (although notably, the Spacebook entry mentions one singular instance of body-theft). While the identities of the Master's first regeneration cycle's incarnations are not named by this story, and the unique cases of the multiple Ainleys and of the "Tzun" regeneration are not addressed, it does account for most regenerations of the Master to have appeared in spin-off media at the time.

Off-screen relationships
Although they played antagonists on screen, in real life Roger Delgado and Jon Pertwee were actually close friends. In interviews and convention Q&A sessions, Pertwee often cited the death of Delgado as one of the factors that led him to give up the role. (DOC: PanoptiCon 93, MM VHS 15)

Long before Tom Baker met Anthony Ainley during the filming of Baker's final serial, Logopolis, he had lived with his brother, Richard Ainley, an acting instructor. Tom often saw Anthony, who would come over to play with Richard's children, but always thought of him as mysterious.

The Doctor Who Fun Book
A glimpse into the Master's life on Gallifrey is provided by the short story NOTVALID: TARDIS Stolen! from 1987's The Doctor Who Fun Book, which is not considered a valid source by this Wiki due to its parodical nature, such as revealing that the Master's true name is "Cuthbert Windbottom", though he is already going by "the Master", a choice of identity the author of the Gallifreyan Gazette article finds unsurprising.

Following the First Doctor's theft of the TARDIS and flight from Gallifrey, the Master is interviewed by the Gallifrey Gazette to give his opinion on the probable motives of his old classmate's crimes; the Master claims that the Doctor had been very excited in the last month over a phone call from "the BB Corporation" and attempts to convince the interviewer that these were surely some of Gallifrey's oldest enemies in whose league the Doctor had entered. Yet another hint as to the Master's activities is the classified ad for "lifelike dolls" to be purchased from him, which heavily suggests that the Master is already in possession, and making illegal use of, a Tissue Compression Eliminator.

Doctor Who The Official Annual 2018
According the Doctor Who The Official Annual 2018, which is not accepted as a valid source for in-universe articles on this wiki due to not constituting a story as such, Missy remained on Skaro after The Witch's Familiar, adopting a Slyther as a pet that ate the Thals she met.

Doctor Who: Legacy
In the story of Doctor Who: Legacy, time travelling Sontarans' attacks on the timeline are felt by the "Saxon" Master. After witnessing the universe collapse with Lucy Saxon on Utopia, the Master, seeking to establish his New Time Lord Empire, leads the Toclafane in overrunning the Sontaran Empire and pursuing the Doctor. As the Doctor's incarnations assemble, the Master likewise gathers his other selves, retrieving his decaying incarnation from the collapsing reality. Next to be summoned is the "UNIT enemy" Master, wielding a paradox generator.

Other matters

 * A distinct incarnation of the Master features in the board game Battle for the Universe.
 * The Companions, a reference book by John Nathan-Turner, established that Melanie Bush joined the Sixth Doctor in 1986 when she helped thwart the Master (presumably ), who planned a dastardly attempt at a massive computer fraud involving all the banking houses on Earth.
 * The 2020 animated version of the Second Doctor serial The Faceless Ones retroactively makes this story the Master's first appearance, though they do not appear in person. He appears on two separate wanted posters, one showing his Roger Delgado incarnation, and another showing the incarnation played by Sacha Dhawan.
 * The character was originally supposed to be killed off for good in The Final Game, which would have seen him sacrifice himself to save the Doctor and reveal that they are split parts of the same personality (the Doctor being the Ego and the Master being the Id). Roger Delgado's death prevented this.
 * He was originally supposed to be the main villain of The Talons of Weng-Chiang, presumably the Peter Pratt incarnation.
 * Planet of Fire was supposed to be his final appearance, as Anthony Ainley's contract was expiring. Dialogue from The Mark of the Rani explaining how he survived was cut.
 * The Master was intended to be the main villain of the cancelled novel To Hold Back Death.
 * Mestizer was intended by Daniel O'Mahony - the author of the books she appeared in - to be an incarnation of the Master.
 * Though Robert Holmes has received a creator credit for the Master in the revived series, no such credit is given for Missy.
 * The version portrayed by Eric Roberts was the first Master to be given an official incarnation-specific name, with the film's soundtrack release referring to him as "The UnBruce".
 * The Doctor Who: Figurine Collection generally did not assign names to incarnations of the Master, with the (DWFC 89),  (DWFC 100),  (DWFC 144) and  (DWFC 187) incarnations all being introduced simply as "the Master". However, the  incarnation (DWFC 49) was named the "Emaciated Master", whilst DWFC 105 specified its release being " as Professor Yana".

Audio
Geoffrey Beevers is the main portrayer of the character in Big Finish audio dramas. Sometimes, as in Fourth Doctor Adventures, he's merely reprising the pre-Tremas Master seen in The Keeper of Traken. On other occasions, he has portrayed a post-Survival Master that had had Tremas's body stricken away. On two more occasions, Mastermind in 2013 and Day of the Master in 2019, he played a post-TV movie Master, who is established as always returning to the same emaciated form even as he takes over the bodies of others.

Alex Macqueen portrayed the Master in Dominion, Time's Horizon, Eyes of the Master, The Death of Hope, The Reviled, Masterplan, Rule of the Eminence, Vampire of the Mind and The Two Masters, set at a time where the Master is given a new regeneration cycle by the Time Lords after his confrontation with the Eighth Doctor, and is set to work on their behalf.

In The Two Masters, it is revealed that the Beevers and MacQueen Masters had switched bodies due to the manipulations of the Cult of the Heretic, with the result that the two actors were technically portraying each other's version of the Master in the audios And You Will Obey Me and Vampire of the Mind respectively. In the former, the Macqueen Master in the Beevers Master's body lost his physical form; he briefly took over the body of Michael Masterson(as played by Russ Bain) before said body decayed back into a replica of the Master's previous Time Lord body, once again being voiced by Geoffrey Beevers.

Derek Jacobi returned as the Master in his own audio series, The War Master, as well as Gallifrey: Time War. He portrayed the same incarnation as seen in Utopia, yet set before that incarnation turned himself human. Michelle Gomez's Missy was given her own series as well in 2019.

James Dreyfus portrayed the Master in The Destination Wars, The Home Guard and The Psychic Circus. As well as Dreyfus, the Master, through the use of a voice filter, temporarily assumes the voice of the First Doctor, as played by David Bradley. The announcement of his casting on the Big Finish website referred to him as "the first incarnation of the Master". This would make him the adult version of William Hughes' incarnation, although him being the First Master is not explicitly mentioned in his audio stories.

Milo Parker played the Master during his time at the Academy in Masterful.

Additionally, in The Hollows of Time, an audio adaptation of an unrealised 1980s Sixth Doctor script made as part of The Lost Stories range, a character called Professor Stream appears, played by David Garfield. While he was supposed to be revealed as the "Tremas" Master in the original script, he was not identified as the Master in the audio version, and the audio is narrated by the Doctor and Peri as a flashback, where their memories are partially distorted, leaving them both uncertain as to Stream's true identity.

Anagrams
During Anthony Ainley's tenure as the Master, pseudonyms made from anagrams of the actor's name were often used in the credits for the Master's disguises, such as "Neil Toynay" for the Portreeve in TV: Castrovalva. "Tremas" is itself an anagram of "Master".

The tradition continued in the BBC Wales version of the show. During Series 3, the Master takes on two new identities, "Professor Yana" in TV: Utopia, and "Mr. Saxon" in TV: The Sound of Drums. "Yana" is an intentional acronym of "You Are Not Alone", the final words of the Face of Boe, which led the Doctor to discover that Professor Yana was a Time Lord. "Mister Saxon", as the character was mysteriously referred to throughout series 3, is an anagram of "Master No. Six" - John Simm's rendition being the sixth on-screen version of the character. However, showrunner Russell T Davies has claimed that the anagram was unintentional.