The Master

The Master — sometimes called Koschei and many other temporary aliases — was a renegade Time Lord and the Doctor's arch-nemesis.

Although they were originally boyhood friends, (TV: The End of Time, PROSE: The Dark Path) one of the Master's top goals was to destroy the Doctor while acting on a number of schemes, both petty and gross. (TV: The Deadly Assassin, Castrovalva, Time-Flight, Doctor Who)

The Master was referred to as a "jackanapes" and an "unimaginative plodder" by the Third Doctor, (TV: Terror of the Autons) the "quintessence of evil" by the Fourth Doctor (TV: The Deadly Assassin), High Council Borusa found that he was "one of the most evil and corrupt beings [the] Time Lord race [had] ever produced." and noted that the Master's "crimes [were] without number and [his] villainy without end.", (TV: The Five Doctors) "pure evil" by the Eighth Doctor, (TV: Doctor Who) and "[the Time Lord's] most infamous child" by the Time Lord society founder Rassilon. (TV: The End of Time)

After the Last Great Time War, the Master was forgiven for his crimes and called "stone-cold brilliant" twice by the Tenth Doctor and offered to travel the universe with him. (TV: Last of the Time Lords, The End of Time)

It was eventually discovered that the Master's diabolical madness was at least partially the result of a genuine malady in the form of a never-ending drumming sound had been retroactively implanted inside his head by the Time Lords on the last day of the Last Great Time War to further their own goals, possibly meaning that the Master was evil because the Time Lords made him that way. (TV: The End of Time)

Early life
The Master was originally known as Koschei when he grew up on Gallifrey in the House of Oakdown. (PROSE: Divided Loyalties)

Despite his childhood being one more a life of duty, (TV: The End of Time) he had a friendship with the First Doctor. (GAME: Destiny of the Doctors) The two youths would play in the fields near Koschei's home which was his father's estates, with pastures of red grass near Mount Perdition. (TV: The End of Time) They used to sneak out of the Capitol and drink with the Shobogans. (PROSE: The Eight Doctors) On one of these outings, Koschei picked a fight with six drunken Shobogans. (PROSE: UNIT Christmas Parties: Christmas Truce)

Like all Time Lords, Koschei was taken for his initiation at the age of eight. During the ceremony in which he gazed into the Time Vortex through the Untempered Schism, Koschei went mad. This manifested itself as the constant drumming he heard ever after, worsening with time. (TV: Utopia / The Sound of Drums / Last of the Time Lords) Unknown to Koschei, the drumming had been implanted retroactively into his mind by Rassilon as a link to later free the Time Lords from the time-lock imposed upon them. (TV: The End of Time)

During their childhood, Koschei and the Doctor had been mercilessly and viciously bullied by a boy called Torvic; the young Doctor was eventually forced to kill the bully to save his friend's life. He was later confronted by the personification of Death, who insisted he become her disciple. The Doctor refused and suggested Death make Koschei her champion, to which she agreed. The Doctor had ever since felt partly responsible for Koschei. (AUDIO: Master)

At the Academy, Koschei joined a clique of young Time Lords called the Deca. The Doctor and other future rivals Ushas and Magnus also belonged to the Deca. (PROSE: Divided Loyalties) The Doctor and Koschei were also part of the Gallifrey Academy Hot Five, in which Koschei played the drums. (PROSE: Deadly Reunion) Koschei would also hypnotise people, likely as a joke, but anyone he did hypnotise the Doctor could un-hypnotise. (PROSE: The Dark Path)

Whilst at the Academy, the Doctor and Koschei travelled into Gallifrey's past in search of Valdemar. They found nothing of the Old Ones except for warnings. Koschei was fascinated by the power that Valdemar represented while the Doctor was horrified. (PROSE: Last of the Gaderene)

After the First Doctor fled Gallifrey in his stolen TARDIS, Koschei left Gallifrey as well, surprised to find no one chasing him. However, his unstable obsession with order prompted the Time Lords to plant the Time Lady Ailla as a spy to monitor his actions. She posed as a human so Koschei would take her on as his companion during a stopover in the 28th century.

Koschei caught up with the Second Doctor at the Darkheart colony in the early years of the Federation. The temptation posed by the Darkheart device proved too much for Koschei, and the revelation that Ailla was a spy killed the last traces of good in him. After the Doctor trapped him in a black hole, Koschei swore to take revenge. (PROSE: The Dark Path)

Nemesis of the Third Doctor
After he escaped the black hole (at the cost of his remaining regenerations), the Master was imprisoned on Shada, by the Time Lords. However, the Time Lords decided to keep the Doctor busy by releasing the Master. This happened just before the Third Doctor's first confrontation with him. (PROSE: Prisoners of the Sun)

Before the Third Doctor was made aware by the Time Lords of his presence, the Master had in fact been on Earth for some time.

The Master was present at the first Auton invasion of Earth. He had apparently seen or heard about Channing attempt to capture the Third Doctor. He contacted journalist James Stevens by phone, whose article he had read in the Daily Chronicle, and told him about the near-kidnapping.

He later called Stevens again, during the Silurian attacks on Wenley Moor. He informed Stevens that Frederick Masters had been the first to have died from the plague sweeping London.

Shortly after the Inferno Project incident, the Master once more contacted James Stevens, this time to check up on his work on his U.N.I.T. article. He promptly hung up when Stevens mentioned C19 and Glasshouse. (PROSE: Who Killed Kennedy)

He first infiltrated the headquarters of UNIT while the Brigadier and the Doctor had gone to meet with government officials. He hypnotised the Doctor's assistant Liz Shaw and, through her, learned of recent events, including the recent failed Nestene invasion and the awakening of the Silurians. This inspired him to ally himself with them and to locate any more Silurian colonies. (PROSE: Reconnaissance) The Master invented the Keller Machine, and spent many months establishing his and its credentials. (TV: The Mind of Evil)

The Master appeared at a circus, his TARDIS in the form of a circus trailer or horse box. He hypnotised the circus troupe to obey his orders as part of his plan to assist the Nestenes in their latest bid to conquer Earth. A Time Lord emissary alerted the Doctor to his rival's presence on the planet. After the failure of his plan, the Master fled. The Doctor had already taken his dematerialisation circuit, however, preventing the Master from leaving Earth in his TARDIS. (TV: Terror of the Autons)

The Master returned again, posing as the scientist who had "developed" the Keller Machine, in reality a living alien entity. He used prisoners as a plan to hijack a missile containing nerve gas and use it to cause a conflict that would trigger a nuclear war. The Doctor stopped him amd destroyed the missile but earlier was forced to give hin his dematerialisation circuit back, giving the Master freedom. (TV: The Mind of Evil)

Shortly after the Master regained control over his TARDIS, he tried to gain control of a cult so he could harness the power of the Immortals. He convinced the real cult leader, Hadley, that he could serve the cult loyally, by supplying them with sarg. Unfortunately for the Master, Hadley only intended to keep the Master alive while he was still useful. With no other options, the Master formed a temporary truce with the Doctor to stop Hades' plan. After the crisis was resolved, the Doctor allowed the Master to depart unmolested in the name of their temporary truce. (PROSE: Deadly Reunion) The Master eventually recovered full functionality of his TARDIS and brought Axos to Earth hoping to ally himself with them. Instead, he became the prisoner of Axos,and only escaped by saying that he would help it. The Doctor tricked the Master into thinking he was going to betray Earth. Instead, he trapped the Master with Axos in a time loop. (TV: The Claws of Axos)

Utilising records stolen from the Time Lords the Master, posing as an Adjudicator, travelled to a human colony on the planet Uxarieus in the year 2472. There the records indicated he would find the Doomsday Weapon created by a near-extinct native species. Once again the Doctor defeated his plans. (TV: Colony in Space)

In the Wiltshire village of Devil's End, the Master summoned the Dæmon Azal, but failed to understand the power and control that was necessary following summoning him. Following Azal's confrontation with Jo Grant's selflessness he was captured by UNIT after failing to escape in the Doctor's car; Bessie. (TV: The Dæmons) After a trial by human authorities, the Master was sentenced to life-long imprisonment in a prison on an island designed especially to hold him. (TV: The Sea Devils) The government used him as a scapegoat for all the alien attacks that had occurred. (PROSE: Who Killed Kennedy)

Before his trial, the Master was sent to Stangmoor Prison, but during his captivity, an army of hypnotised salespeople stormed the prison. This was an attempt to rescue him, but the attempt failed and the Master was sent to another secure holding facility. Meanwhile, the Doctor and Jo were trapped in an extra-universal prison by the Freedom Corporation, so the Brigadier was forced to strike a deal with the Master to save them. But the Master double-crossed him and uses time-travel technology to regress the Earth backwards in time. However, with help from the Time Lords, the Doctor was freed and was able to stop the Master's plan and restore everything to normal. (PROSE: Freedom)

Before he was sent to Fortress Island, the Master was sent to Aylesbury Grange Detention Centre. The Doctor visited the Master, who insisted he had changed, only to reveal he had escaped. The Doctor was speaking to a hologram. The Master nearly escaped, but was stopped by soldiers. The Doctor revealed he had been a hologram as well. (COMIC: The Man in the Ion Mask)

While in custody, with the Doctor gone to Peladon, (TV: The Curse of Peladon) the Master collaborated with UNIT to prevent an invasion by a fascist version of Earth, travelling with the Brigadier and Ian and Barbara Chesterton to that alternate universe and encountering an alternate version of himself. This alternate Master was imprisoned and tortured by order of the Leader of the Republic of Great Britain, that reality's version of the Doctor. The Master killed his other self, claiming it was an act of mercy. (PROSE: The Face of the Enemy)

Some time during his obvious actions against the Doctor and UNIT, the Master infiltrated the government's Department C19 to a shocking degree. He took control of the Glasshouse, a facility for traumatised UNIT soldiers, and in particular Private Francis Cleary. He also tried to undermine UNIT in the short term. In the long term, he planned to use a time ring to have Cleary go to 1963 to prevent the Kennedy assassination, thereby altering Earth's history to make it more vulnerable to invasion. The plan failed. (PROSE: Who Killed Kennedy)

In a later encounter, the Master created a device that switched his mind with the Doctor's. He went to the Doctor's TARDIS, where he learned that the Time Lords had made the TARDIS unpilotable by the Doctor. Before returning to the TARDIS, the Master asked the Brigadier to move him to a new holding facility with a good view and told Mike Yates to ask Jo Grant out on a date. (PROSE: The Switching)

When he was finally sent to Fortress Island, the Master quickly gained control over his jailer, George Trenchard, and nearly caused a war between humans and Sea Devils, a species related to the Silurians. He later escaped in the confusion. (TV: The Sea Devils)

The Master travelled to ancient Atlantis and, confronting the Doctor there, brought forth Kronos, king of the Chronovores. Kronos captured him but allowed him to go free. (TV: The Time Monster) Returning to 1970s Earth, he used time-displaced Scottish warriors to seize a nuclear submarine and threaten Britain with obliteration if he wasn't given the Doctor's TARDIS; he ended up temporarily trapped in the 18th century. (COMIC: The Glen of Sleeping) He also worked with the Gaderene race to conquer Earth. (PROSE: Last of the Gaderene) He forged a short-lived alliance with the Daleks, acting as their agent to provoke warfare between the Earth Empire and the Draconian Empire in the 26th century. To achieve this, he employed a force of Ogrons who, through the use of hypnosound, made themselves appear human or Draconian, thus provoking the other side. When the Doctor revealed the true perpetrators, the plot was abandoned. (TV: Frontier in Space)

For a short while the Master adopted the identity of Duke Dominus, a gangster on early 20th century Earth, but his plan on this occasion was halted by the Fourth Doctor without the Master even knowing it. (PROSE: The Duke of Dominoes)

Decaying Form
The Master finally went under cover on Earth following the 22nd century Dalek invasion and killed David Campbell, the husband of the Doctor's granddaughter Susan. After being defeated by the Eighth Doctor he fled in his TARDIS taking Susan with him as a hostage unaware of her Gallifreyan heritage. As his TARDIS materialised on Terserus she used his TARDIS' telepathic circuits to attack him, forcing him out onto the surface of Terserus. Utilising his own Tissue Compression Eliminator against him while he was holding the Dalek's transmuter. The blast severly deformed and nearly killed him. Susan Foreman departed in his TARDIS, this brief materialisation however alerted the Time Lords to the Master's presence on Terserus. (PROSE: Legacy of the Daleks)

Investigating the materialisation of an unauthorised TARDIS the Time Lord Chancellor Goth arrived on Tersurus and found the Master in a wasted condition; that of a decaying animated corpse. The Master sensed that Goth wished for power and offered it to him, whilst Goth thinking that the Master was a dying "creature" thought he could control the Master for his own means. (PROSE: Legacy of the Daleks, TV: The Deadly Assassin)

The Master made Goth, in line for the position of Lord President of the High Council of Time Lords, into his slave, continuing the promise him power. Whilst on Gallifrey he also took over the mind of Solis, one of the Chancellory Guard. With a telepathic summons and a vision of the future created by the Matrix, the Master lured the Fourth Doctor to Gallifrey to seemingly prevent the murder of the then-serving Lord President. The Doctor failed and ended up on trial for the President's murder. Whilst the Doctor was on trial the Master killed others on Gallifrey through the use of his Tissue Compression Eliminator, leaving them to be found like a grisly calling card for the Doctor.

Secretly, the Master had access to the Matrix. He also had guessed the secret of the Eye of Harmony and various artefacts left behind by Rassilon. He realised that the Eye of Harmony; a black hole, resided beneath the Panopticon and, realising that it had immense power, believed he could use the Sash of Rassilon to protect himself from the raw power of the Eye and the destruction that unleashing it would cause. He thought that it could channel that energy to renew himself.

The Doctor defeated the Master in physical combat and he appeared to have fallen into a crevice created by a localised earthquake. In fact, he had gained access to his TARDIS, disguised as a grandfather clock, and escaped. (TV: The Deadly Assassin)

After escaping from Gallifrey, the Master had entered into an alliance with the Kraals, and claimed to help them invade the Earth in 1979. (AUDIO: The Oseidon Adventure) He tried to achieve this by looking for a genetically engineered alien worm, whose purpose was to generate wormholes in space. The worm had been living in Derbyshire for centuries and had passed into folklore, however, it had taken the form of a woman called Demesne Furze. While he was looking for the worm, he allied himself with Colonel Spindleton, where they both met the Fourth Doctor and Leela. However, the Master generated a storm, using a lightning bolt from it to activate the worm's ability to create wormholes, in turn, generating a wormhole to Oseidon, but also killing the worm. (AUDIO: Trail of the White Worm)

Upon arrival on Earth, the Kraals, led by Marshal Grinmal, double-crossed the Master and imprisoned him with Leela, while they sent the Doctor to Oseidon to be interrogated by Chief Scientist Tyngworg. However, the Master and Leela escaped through the wormhole and infiltrated the Kraal bunker. However, while he was in the bunker, the Master discovered he was an android duplicate, ever since he arrived in Derbyshire, and the Master had been on Oseidon all along, impersonating Tyngworg. During this, the Doctor escaped and reprogrammed the androids to destroy the invasion force. But, as the Master tried to deactivate all the androids, he discovered he was susceptible to the signal, and therefore, he had also been an android all along as well. The Doctor and Leela constructed another Master duplicate, to help them discover the real Master's plan, which was to capture the Z-battery the Doctor left on Earth to repair his TARDIS during his exile. The Master's plan was to use the Z-radiation within the battery, combined with the O-radiation that was on Oseidon, to create ZO-radiation, which had an immense amount of power, which the Master could use to renew himself. The Doctor defeated the Master by using the Master's android duplicate he had constructed to kidnap the Master and take him away in his own TARDIS, before his plan could be fulfilled. (AUDIO: The Oseidon Adventure)

With his TARDIS still in the form of a clock, the Master tried to steal Iris Wildthyme's body. (PROSE: The Scarlet Shadow)

The Master was drawn to and became stranded on the planet Traken, the centre of the Traken Union, in a TARDIS configured into the sculpture-shaped Melkur. The Master plotted to take over the Source also located on the planet Traken, the power behind the Traken Union and use it to restore himself. To this end, over a period of years, he won over Kassia, who later married Tremas and became a stepmother to Nyssa. His plans were thwarted when the Keeper summoned the Fourth Doctor and Adric who had sensed something of his machinations. With the help of Tremas and Nyssa, the Doctor removed the Master from the Source.

However, with some of the Keeper's powers lingering, the Master merged with Tremas, stealing his body. (TV: The Keeper of Traken, Logopolis)

However, because Tremas' body was not that of a Time Lord, it could not regenerate but would age instead. If he wanted to survive, the Master would have to steal another body.

Tremas Form
The Master, in his new Traken body, went to Earth, where he trapped the Doctor's TARDIS in a gravity bubble. He killed Tegan's aunt Vanessa and a police constable with his Tissue Compression Eliminator. He went to Logopolis, where he pretended to be Tremas to get Nyssa's cooperation, giving her a bracelet that allowed him to control her arm. Using her as a hostage, he perverted the Block Transfer Computations and held the planet for ransom until its secret was revealed. This made the causal nexus unravel and release an unstoppable wave of entropy to destroy the universe. He also broke the Logopolitans' blockade of entropy, allowing it to swallow several galaxies, including the entire Traken Union.

The entropy wave was so threatening that the Master agreed to work with the Fourth Doctor to stop it. They travelled to the Pharos Project on Earth to do so, using the last theorem of Logopolis to reopen Charged Vacuum Emboitments, or CVEs. His true plan was revealed however, when he sent a message to the peoples of the universe that he would stop the entropy only if they submitted to his rule. While stopping the Master's signal to shut down the CVE that would halt the entropy wave, the Doctor fell off the Pharos Project's radio telescope and regenerated, allowing the Master to escape. (TV: Logopolis)

The Master kidnapped Adric and held him in a hadron web to make him a part of his TARDIS. Using a projection of Adric on board the TARDIS, the Master sent the newly-regenerated Fifth Doctor hurtling to destruction at Event One, but the Doctor saved his TARDIS through the Architectural Configuration. The Master used Adric's block transfer computations to create Castrovalva in the Andromeda Galaxy, where the Doctor would recover from his regeneration. He escaped from the recursion trap and tried to kill the Doctor, but was attacked by the enraged citizens with the city itself due to collapse. (TV: Castrovalva)

The Master escaped from Castrovalva, however, in the attempt, it caused damage to the dynamorphic generators, making it difficult to continue piloting his TARDIS. (PROSE: The Quantum Archangel) He travelled to Earth in 140,000,000 BC, where he disguised himself as the magician Kalid, hoping to use the Xeraphin gestalt to replace his dynamorphic generators. He brought two Concordes to his Citadel via a time contour. The second held the Doctor, his TARDIS and companions. He originally planned to use the captured passengers to break into the Sanctum and take control of the Xeraphin and add him to his TARDIS, but then he acquired the Doctor's TARDIS in a trade with him for a part the Doctor needed for his own TARDIS.

The Xeraphin contacted Nyssa and let Tegan and her enter the Citadel, where he revealed his true form. The Master held the passengers hostage for parts from the Doctor's TARDIS. The second Concorde was returned to its own time and the Master ended up on Xeriphas with the freed and angry Xeraphin. (TV: Time-Flight) On Xeriphas, he found and acquired Kamelion, a shape-changing android that could be easily controlled by a stong mind. Managing to elude Xeraphin, the Master escaped to 1215, England. Disguising himself as the French knight Sir Giles and made Kamelion impersonate John of England to prevent the signing of Magna Carta. However, the arrival of the Doctor caused interference with his plans. After the Doctor defeated him in a joust, the Master fled in his TARDIS after the still-disguised Kamelion offered the Doctor the choice of saving him or another captive. (TV: The King's Demons)

Directly following these events, the High Council of the Time Lords discovered that earlier incarnations of the Doctor had been taken into the Death Zone on Gallifrey. They asked the Master for help and offered him a new cycle of regenerations. He agreed and was given a copy of the Seal of the High Council by the Castellan. The Doctor's third incarnation did not believe him and took the seal from him. He made a temporary alliance with the Cybermen to guide them to the Dark Tower. He informed the First Doctor how to get past security, but then grew power-hungry at the mention of immortality. Brigadier Lethbridge-Stewart knocked him unconscious and Sarah Jane Smith and Tegan Jovanka bound him. After Borusa was encased in Rassilon's tomb, Rassilon sent the Master back to his own time. (TV: The Five Doctors)

The Master arrived in Camelot just after the coronation of King Arthur. He became the Merlin after the old one had died. He planned to make Arthur believe Mordred was dead so Mordred would grow up to kill Arthur at the battle of Camlan.

The Doctor and Tegan arrived, met Arthur and told him about the Master. Arthur summoned the Merlin to test their truthfulness. When the Master saw the Doctor and Tegan, he told Arthur he had no intention of harming him. He left the court and hurried to his TARDIS, which was disguised as the turret room of Arthur's castle. The Doctor suggested Arthur create the Knights of the Round Table so when Mordred came they would be ready. (PROSE: The Creation of Camelot)

The Master developed a more powerful version of the Tissue Compression Eliminator and accidentally shrank himself and his lab, without the ill effect of death. Using a device to boast his telepathy, the Master made contact with Kamelion once more, directing him to use the Fifth Doctor's TARDIS to land on planet Sarn. With Kamelion acting as his physical proxy, the Master had him pretend to be the locals' god and order the Doctor's death. When this failed, he had Kamelion take the small box his lab had become and take it to the lab on Sarn that used Numismaton Gas, hoping it could restore him. As the Master stood in a gas vent and returned to normal size, the Doctor used the gas to burn him (apparently) to death. (TV: Planet of Fire) However, the Numismaton Gas increased the power of the Source of Traken still remaining in the Master body. (PROSE: The Quantum Archangel) He went in search the Fountain of Youth to restore himself, which he managed to exploit. (PROSE: A Town Called Eternity)

A hallucination of this incarnation of the Master appeared to the Fifth Doctor as he lay dying of spectrox toxaemia in the TARDIS. (TV: The Caves of Androzani) This was due to the Master's attempts to psychically interfere with the Doctor's fourth regeneration. (AUDIO: Winter)

The Master allied with the Rani (whom he knew as a member of the Deca on Gallifrey) in Killingworth, an early 19th century English mining village, against the Sixth Doctor and Peri Brown; he hoped to hasten the advancement of Earth's technology for his own nefarious reasons while the Rani wanted the brain chemical that induced sleep. The Doctor trapped the Master and the Rani in her TARDIS, which the Doctor had sabotaged; time spillage put them in danger of being eaten by a Tyranosaurous Rex. (TV: The Mark of the Rani) The Master separated the Rani's console room from the rest of her TARDIS, leaving her to drift aimlessly through the vortex. (PROSE: State of Change)

Recovering his own TARDIS and learning of the Valeyard, the Master materialised in the Matrix and observed the Sixth Doctor's trial on Space Station Zenobia while examining the Matrix footage himself to see what was tampered with. He considered the Valeyard a rival and rescued the Doctor rather than have the Valeyard win as the darker version of his foe was someone he believed unbeatable. He used Sabalom Glitz, always ready to work with anyone for a quick grotzit, as a tool. He tried to steal secrets from the Matrix, but he was double-crossed by the Valeyard, and imprisoned in the Matrix with a limbo atrophier. (TV: The Ultimate Foe) After escaping from the Matrix, the Master could regenerate his body because the Source of Traken still existed within him. (PROSE: The Quantum Archangel)

After escaping from an unsuccessful alliance with the Krotons, the Master discovered that the last remnants of the Source of Traken were fading, so his previous cadaverous form would return and he would die. Meanwhile, he was attacked by the Chronovores looking for revenge after he tortured Kronos. The Master devised a plan to destroy the Chronovores and achieve omnipotence by trying to access the Lux Aeterna using the son of TOMTIT, the TITAN Array. He stole the equipment and used it upon a woman he hypnotised, Anjeliqua Whitefriar, expecting it to destroy her before he used it. However, she absorbed the Lux Aeterna, achieved omnipotence and became the Quantum Archangel. Using her power, she filled the universe with too many alternate timelines, leading the Chronovores to feast upon them, eventually leading to the end of the Universe. The Master (fully returned to his cadaverous form again) and the Doctor teamed up to rectify the Master's mistake by defeating the Quantum Archangel. They discovered that the Quantum Archangel had allied itself with the Mad Mind of Bophemeral so it could have infinite knowledge of the Universe. The Doctor and the Master encountered Kronos, who claimed to have been the one who attacked the Master's TARDIS, so he would come up with his plan, and would eventually lead to the Master's destruction as well as allowing Anjeliqua to survive, causing Kronos' plan for revenge to go wrong. They succeeded by draining the Lux Aeterna out of her, although not before the Master escaped using the TITAN equipment to harness the Lux Aeterna to restore his Tremas body. (PROSE: The Quantum Archangel)

After trying to start a war between Antari Two and Antari Three, (PROSE: First Frontier) the Master went to the Cheetah World, where he took control of the Cheetah People and the kitlings. He sent them to Ace's home in the London suburb of Perivale and hunted for human recruits. At the same time, exposure to the planet had changed him into a Cheetah Person. He found a pliable young man called Midge and used him to escape. The Seventh Doctor and Ace found him. The Master killed Midge and teleported the Doctor to the Cheetah World, which had begun to break up. The Doctor escaped but the Master was trapped on the dying world. (TV: Survival)

Aftermath
How exactly the Master escaped the Cheetah World was a matter of debate. Several competing theories existed.

Finding a new regenerative cycle in the past
One idea about the Master's escape from Cheetah World had it that he escaped with the aid of a Kitling just as the planet exploded. The explosion of the planet sent him back in time to Earth in 1957.

Trapped on Earth at the dawn of the Space Age, the Master interrupted the real first Soviet satellite launch and sent a distress signal to the Tzun Canton on Zeta Reticuli Four. He offered to help assimilate Earth into the Tzun Confederacy. In return the Master asked for passage off Earth and the use of the Tzun's genetic engineering to cure his Cheetah Virus infection. The Tzun accepted, they prepared nanites for him that broke down the corrupted Trakenite DNA in his cells and restructured it. This restored the Master to being a "full" Time Lord which gave him a new regenerative cycle. While assisting the Tzun, the Master used the alias Major Kreer. Shortly after being restored to his full Time Lord heritage he was shot in the back by Ace causing him to regenerate. Following the regeneration he was able to make his escape, summoning his TARDIS using a Stattenheim remote control, built from Tzun technology. After leaving a booby-trap for the Seventh Doctor in a nuclear warhead, the Master fled. (PROSE: First Frontier)

Later, the Master laid a trap for the Doctor in one of the Doctor's homes using a device which would release the energy from a time fissure once the Doctor's TARDIS materialised. This would destroy it. The plan failed when Sarah Jane Smith, Mike Yates and K9 destroyed the device, causing the Master to flee. (PROSE: Housewarming)

The nanites the Tzun gave the Master eventually began to fail, causing him to seek the Loom of Rassilon's Mouse in order to make himself a new body. The plan failed and the Master managed to escape by hypnotising Kitai into posing as a decoy. (PROSE: Happy Endings)

Tremas Form persists
Another theory held that the Tremas Master simply continued to exist after his time on Cheetah World, and that he remained infected by the Cheetah Virus for quite some time. On Earth, he tried to cure the virus by extracting nutrients from dying humans. (PROSE: Stop the Pigeon) The Master next tried to gain a new body from legendary aliens, the Fleshsmiths. The Master's plan was stopped by the Doctor, who ejected the new body from the Fleshsmith vessel into space. (PROSE: Prime Time) According to this version of history, it wasn't at all clear how the Master rid himself of the virus that had so plagued him.

At some point, however, the Master captured the first seven of the Doctor's incarnations and put them into a void called the Determinant. The Graak freed the Doctors and the Master was put on trial. (GAME: Destiny of the Doctors)

Tremas Form lost
A third account failed to touch on any ill-effects of the Master's interaction with the Cheetah People. Focussed instead on the latter part of the Tremas Master's life, it suggested that at some point, the Master learned of a device known as the Warp Core, a sentient powerhouse of mental energy designed as a weapon to safeguard the planet Duchamp 331. He tracked the Warp Core to Earth, intending to use it to power his TARDIS. Unprepared for its power and underestimating its outside awareness, he was attacked by the Warp Core, having the body he stole from Tremas stripped from him, reducing him to his previous, decaying form. The Master then used a mask to disguise his deformity and followed the Warp Core as it arrived on Duchamp 331. (AUDIO: Dust Breeding) The Seventh Doctor made a deal with Death whereby the Master would have ten years of peace and sanity, at the end of which the Doctor had to kill him. The still-scarred Master had become a physician with no memory of his past, and took the name Doctor John Smith. The Master was taken in by Wilston-Croft, and inherited his house when Wilston-Croft died. During his ten years as John Smith, the Master had become emotionally involved with a woman named Jaqueline Schaeffer.

At the end of the allotted time, the Doctor duly arrived but strove to avoid fulfilling his side of the bargain. The Master became aware of the Doctor's role in pledging him to Death as her servant but forgave him for it. Death herself was present, disguised as the Master's maid, and manipulated events so that the John Smith persona would crumble and the true Master become dominant once more. (AUDIO: Master)

Stealing the Doctor's lives
After he was tried and executed by the Daleks on Skaro as part of a Time Lord-Dalek treaty, (PROSE: Lungbarrow) the Master's "last wish" was for his remains to be transported to Gallifrey but his essence survived in a fluid-like form that was either a morphant (COMIC: The Fallen) or a deathworm (PROSE: The Eight Doctors).

The Seventh Doctor stored the ashes in a casket and set his TARDIS on course for Gallifrey. En route, the Master, whose consciousness had survived the death of his physical body, escaped from the casket and interfered with the TARDIS, causing a timing malfunction. The ship materialised in San Francisco during the final days of 1999.

On exiting the TARDIS, the Doctor was caught in a crossfire of a gang war and was picked up by an ambulance. As he lay wounded, he saw the Master's form exiting the TARDIS via its keyhole, but he was unable to communicate this information to the humans nearby. Bruce tended to the Doctor, but while he was loading him into the ambulance, the Master hid inside a bag. Later, after Bruce had gone to home and bed, the Master forced his way into Bruce's body through his mouth, killing him and taking over his body. (TV: Doctor Who)

The next morning, the Master awoke, now inhabiting Bruce's body. He realised the decaying form would not last long and launched his scheme to steal the Doctor's remaining regenerations. His first act was to kill Bruce's wife Miranda.

The transformation into Bruce involved some complications. His eyes retained the "cat's eye" appearance, a holdover from his experiences on the Cheetah World, (TV: Survival) forcing him to wear sunglasses to remain inconspicuous. Also, Bruce's body began to decay rapidly.

The Master befriended Chang Lee, a young gang member who had been present when the Doctor was shot, and who had stolen the TARDIS key. With Chang Lee's help, he entered the Doctor's TARDIS and regaled Chang Lee with stories of the Doctor's supposed villainy (claiming, among other things, the Doctor had stolen the Master's regenerations). As part of his plan to take the Doctor's lives, he intended to open the Eye of Harmony, destroying the Earth in the process. With Chang Lee's further help, he was able to open the Eye. He discovered that the Doctor had regenerated into a new form, and that the Doctor was half-human. This answered a few of the Master's longstanding questions about his foe.

After fully regaining his memory, the Eighth Doctor and his companion, Dr. Grace Holloway, made their way back to the TARDIS where the Master, now dressed in Gallifreyan robes, greeted his enemy. In the ensuing battle, the Master used mind control on Grace. He also killed Chang Lee by snapping his neck when Lee realised the truth about the Master after the Master accidentally revealed that he had wasted all of his lives in fighting the Doctor, rather than the Doctor having stolen them.

Although the Master was able to initiate the transfer process that would give him access to the Doctor's remaining lives, Grace was able to prevent this by rerouting the TARDIS' power and sending the ship into a temporal orbit. With the Master's body dying as the Doctor's regenerations were returned to him, the two Time Lords fought near the Eye of Harmony, culminating in the Master falling into it when he leapt at the Doctor and misjudged the angle. The Doctor said he had been "eaten" by the TARDIS. (TV: Doctor Who)

Shortly after his defeat, the Master laid a final trap for the Doctor, leaving a crystalline structure on the Eye that would give the Doctor amnesia. (PROSE: The Eight Doctors)

Beyond the Eye of Harmony
After the Master passed through the Eye of Harmony, (TV: Doctor Who) his essence was left wandering the Time Vortex and close to extinguishing. Eventually he was rescued from the Vortex by a being named Esterath, the then-controller of the Glory, the focal point of the Omniverse. The Master was told that it was time for the Glory to gain another controller, but the power had to be fought for. The Master assumed that the battle would be between himself and his greatest foe, the Doctor. (COMIC: The Glorious Dead)



After gliding over the many realities throughout the Omniversal Spectrum for what he described as seeming like centuries, the Master was resurrected into the body of a recently-deceased vagrant on the streets of 2001 Brixton. Some weeks afterwards, the Master was transported onto the Moon during one of the Doctor's adventures (due to a symbiotic link he had formed with the Doctor's TARDIS, when it consumed part of his essence after he passed through the Eye of Harmony). The Master subsequently used this link to trail the Eighth Doctor for some time without his enemy suspecting - even after they had met face to face. (The Glorious Dead)

He was present in London during the crisis resulting from Grace Holloway's attempt to merge human and Time Lord DNA (the alien DNA was in fact that of a Morphant). He killed an MI6 agent with the TCE at this time, but fortunately for the Master the Doctor departed before his trademark was discovered. (COMIC: The Fallen)

The Master later made contact with Sato Katsura, a Japanese samurai unwillingly rendered immortal as a result of his involvement in the Doctor's adventures. The embittered warrior became the Master's follower. At his behest, Sato adopted the identity of Cardinal Morningstar and became leader of the Church of the Glorious Dead, instigator of a holy war that altered the history of Earth, a planet now renamed "Dhakan".

The symbiotic link between the Doctor's TARDIS and the Master had also given the latter the ability to influence the flight of the TARDIS, which he used to send the craft to times and places which would weaken the Doctor's self-belief and confidence. This done, the two fought for the Glory, with the Master apparently triumphant.

It would soon be time for the Glory to gain another controller, but the power had to be fought for. The Master assumed the fight would be between himself and his greatest foe. He was mistaken. The true battle was between his companion, Sato, and the Doctor's, the Cyberman Kroton. Kroton was the victor. Amongst his first acts as controller of the Glory were to cleanse the TARDIS of the Master's influence and to banish the Master somewhere that he could not escape. The Master declared he would survive and return. (COMIC: The Glorious Dead)

The piece of the Master's essence imprisoned inside the Doctor's TARDIS offered the Eighth Doctor advice through a portrait, a mirror and later the Eye of Harmony. (PROSE: Sometime Never..., The Deadstone Memorial, The Gallifrey Chronicles) Whilst exploring the Eighth Doctor's TARDIS, River Song thought she heard an American screaming from within the walls. (GAME: The Eternity Clock)

The Master escaped the Doctor's TARDIS through the Eye of Harmony by influencing the dreams of Edward Grainger to unravel the Doctor's timeline. The Master was stopped by the First Doctor and Violet after being hit with a rolling pin and being removed from the body he possessed. (PROSE: Prologue)

The Master then managed to evade the Eighth Doctor's detection, and possessed the body of a human native named Richard. (PROSE: Forgotten)

Under the chameleon arch
The Master was resurrected by the Time Lords during the Last Great Time War. They believed that he would be a perfect warrior for the Time War. He was present when the Dalek Emperor took control of the Cruciform. Frightened by the horror of the Time War, he ran away to the end of the universe. (TV: The Sound of Drums) There, he used a chameleon arch to hide himself as a human, Professor Yana. Physically human, Yana believed that he was found on the coast of the Silver Devastation with only an "heirloom" fob watch. His memory of his past was that the watch could never keep time and was always late for things. He believed that he spent his life moving from one refugee ship to another and all his life he heard the sound of drums every waking hour as if they were getting closer. However, it was likely that none of what Yana believed about himself was any more true than that which, for example, John Smith gave to Joan Redfern.

Yana retained the Master's brilliant intellect and ultimately became involved in the attempt to send the remnants of humanity to Utopia. He eventually became friends with another scientist Chantho, who was thought to be the last of the Malmooth race. Together, they worked on the Utopia Project to convey the surviving humans from the planet Malcassairo to Utopia. Yana met the Tenth Doctor, Jack Harkness and Martha Jones, who spoke phrases curiously familiar to him, phrases such as Time Vortex, "extermination", Time War, Daleks and regeneration. Martha made the Professor aware of a watch in his possession. Hearing voices in his mind that commanded and entreated him, he opened it and returned to his true identity. (TV: Utopia)

He then attacked his assistant, killing her even as she shot him in the chest with a laser gun. Fatally wounded, the Master regenerated into a younger incarnation and escaped to Earth in the Doctor's TARDIS. (TV: Utopia)

As Harold Saxon
With his new body, the Master left the Doctor on the planet Malcassairo with Futurekind about to burst in the laboratory door. The Master now had the TARDIS and the Doctor's hand (which Jack Harkness had taken with him to Malcassairo) that contained the Doctor's DNA. (TV: Utopia) Because of the Doctor's last-minute intervention, the TARDIS would only take the Master to Earth in the 2000s. There, he began fabricating Harold Saxon's past to gain political support. He made his first public appearance about eighteen months before the Doctor reunited with his companion Jack Harkness, shortly after the downfall of Harriet Jones. The Master unveiled the Archangel Network, which was hailed as a telecommunications breakthrough. By this point he had taken the identity of Harold Saxon, complete with a fabricated past. (TV: The Sound of Drums)

By December 2007, he had become Minister of Defence of Great Britain. On Christmas Eve, he came to real prominence for the first time, ordering British Army tanks to destroy the Empress of the Racnoss' webstar. (TV: The Runaway Bride, The Sound of Drums)

In 2007, he campaigned for the general election as Prime Minister of Great Britain (TV: Love & Monsters) with the slogan "Vote Saxon". (TV: Captain Jack Harkness) He visited his old high school during the campaign, and as Harold Saxon did not exist, he used the Archangel Network to brainwash staff to gain political support. One teacher, James Curtis, was resistant to the Network, so the Master used his laser screwdriver to implant the appropriate memories into his mind. (PROSE: Speech Day)

"Saxon" asserted that extraterrestrial life did exist and Britain must do something about it. With his election a sure thing, politicians from other parties flocked to his side.

The Master started the Archangel Network. This telecommunications network, tied to mobile phones, carried a mind control signal which made humans trust him. The network affected the Doctor so he had no suspicions as to the Master's presence as "Saxon", though he would have normally noticed the presence of another Time Lord. To those few humans conscious of it, the signal was a persistent drumbeat, the constant drumbeat the Master always heard, that only they could hear.

He also designed the Valiant, UNIT's air carrier, and a laser screwdriver which he reserved for his own use. (TV: The Sound of Drums) "Saxon" funded the rejuvenation experiments of Richard Lazarus. (TV: The Lazarus Experiment)

The Master contacted the Toclafane, the child-like, vicious cyborg remnants of the future humans who had never found Utopia. He cannibalised and converted the Doctor's TARDIS into a paradox machine to change history. (TV: The Sound of Drums / Last of the Time Lords) After Martha had left with the Doctor, he had an agent meet with Martha's mother, Francine, who tapped into a conversation between Francine and Martha via the superphone, which could contact Martha through space and time. (TV: 42)

In 2008, he was elected Prime Minister. He announced first contact with the "friendly" Toclafane who could protect Earth against alien threats.

The Master moved to the Valiant, which the governments of Earth considered neutral territory and therefore fitting for formal first contact with alien life. The Master had the Toclafane murder the President of the United States Arthur Coleman Winters. He captured the Doctor, Jack, and Martha's family, who had come to the Valiant earlier that day. Using the results from Professor Lazarus' experiment along with the DNA in the Doctor's hand, he used his laser screwdriver to age the Doctor one hundred years.

The Master ordered the Toclafane to kill one tenth of humanity and commence their invasion. (TV: The Sound of Drums)

Martha escaped capture on the Valiant and travelled the world. One year later, in 2009, the Master had converted Earth into a slave camp which he ruled from the Valiant. The Master aged the Doctor even further and planned to expand his New Time Lord Empire into space. He built an army of warships to take his war across the universe.

Martha used the legend of the Doctor, which she had spread, and the thoughts of Earth thinking "Doctor" at the same time. Their psychic energy was channelled through the Archangel Network, which the Doctor had spent a year infiltrating telepathically. The psychic energy restored the Doctor and gave him telekinetic powers.

Jack destroyed the Paradox Machine and reversed time one year, although this did not affect anyone aboard the Valiant. Lucy shot the Master. Defeated, he refused to regenerate rather than receive the Doctor's mercy. He died in the Doctor's arms. (TV: Last of the Time Lords)

As far as the general public knew, Harold Saxon "went crazy" and disappeared, along with President Winters. (TV: The End of Time)

The Master was resurrected when his wife Lucy Saxon was imprisoned at Broadfell Prison, London. One of the warders, Miss Trefusis, retrieved the Master's ring from his funeral pyre. On Christmas Eve 2009, the prison governor brought Lucy to a chamber where most of the staff were members of the Disciples of Saxon, who had been working ever since his apparent death to bring about his resurrection.

With the help of the ring and a biometric imprint taken from Lucy, the Master reappeared in a swirl of energy, but Lucy and one other warder had prepared for this. To stop his resurrection, Lucy hurled a Potion of Death at the Master. His followers and Lucy were all killed in the resulting explosion.

The Master survived the blast, but his life force was left in a state of constant depletion. He consumed huge quantities of food and drained the vitality of humans to stay alive. As a side effect of the failed resurrection, he could expend his life force for enhanced agility and send bolts of energy from his hands. He led the Doctor on a wild goose chase after banging the beat of the drums in his mind to lure the Doctor to him and escaped when Wilf interrupted the chase. Encountering the Master soon after, the Tenth Doctor discovered the drumming in his head was not a symptom of insanity, but real. Billionaire Joshua Naismith kidnapped the Master and enlisted his assistance to mend the malfunctioning Vinvocci medical machine, the Immortality Gate. The Master cooperated for his own purposes. He broke out of a straitjacket and flew into the gateway, which he had working a billion fold on the human template. The gateway sent out an energy pulse that transformed every human on Earth, except Wilfred Mott and his granddaughter Donna, into the Master Race - identical copies of the Master subservient to him.

The High Council of Time Lords made contact with the Master using the rhythm of the drumbeats in his head - the same rhythm as the Time Lord's heartbeat - and sent him a White-Point Star, found only on Gallifrey, to boost the signal. Fitting the diamond to a nuclear bolt to boost the signal, the Master tore open the time lock on the war, bringing back the Time Lords.

As the Lord President Rassilon and his council arrived through the Immortality Gate, the Master announced he intended to transplant himself into the entire Time Lord race, just as he had done to the human race. Rassilon, using his gauntlet, reversed the effects of the Master's transplantation, and watched as Gallifrey returned to the universe on a collision course with Earth. The President revealed his plans from the final days of the Time War, but the Doctor stepped in with Wilfred's pistol. After some hesitation, he shot the nuclear bolt holding the White-Point Star, destroying the link.

Rassilon prepared to kill the Doctor, but the Master told the Doctor to step out of the way. He unleashed his bio-electric blasts at the President, roaring that the Time Lords had made him the monster he had become, counting the beat of the rhythm that had resounded in his head and tormenting him all his life. The Time Lords, Gallifrey, and the Master vanished in a burst of white light and were sent to their destruction in the final day of the Time War. (TV: The End of Time)

Personality
Like all Time Lords, the Master's personality varied depending on which incarnation he was in. However one thing that remained constant throughout his life was his determination to become the Master of the universe and his reputation as a psychopath and one of the most evil Time Lords to have ever existed. His first incarnation was driven mad from looking into the Untempered Schism and from Rassilon placing a never ending drumbeat in his head, and this gave him an evil and psychotic personality no matter what incarnation he was in; even regeneration and ressurrection wouldn't stop the drumming. After spending so long hearing it, the Master's final incarnation admitted he wasn't sure what he would be without it and after coming back from the dead he even claimed he had missed the drumming, despite the fact that it had tormented him all his life. (TV: The Sound of Drums, The End of Time)

Some incanations of the Master were very charming and charismatic, while others possessed an almost animal like savagery; his final incarnation was a combination of both. (TV: The End of Time) The Master was a loner and unlike the Doctor he rarely felt the need to have companions and he also showed a blatant disrespect and even distain for Humans, considering them to be a pathetic species. The Master was often willing to sacrifice people to further his own goals, or sometimes cheerfully slaughtered people just for the sake of it. He was sadistic and liked to cause suffering.(TV: Last of the Time Lords)

Nonetheless the Master did have a softer side, which was especially noticeable in his final incarnation. All his evil traits were basically implanted into him by Rassilon through the drum beat that drove him insane, and thus the Master was not entirely to blame for turning out the way he was. He respected the Doctor, considering him to be a worthy opponent, and remembered the friendship they'd had during their childhood. He also sometimes wondered what kind of man he would have become if not for the drumming in his head. Just before Rassilon and the Time Lords were sent back into the Time War, the Master finally displayed a noble and self-sacrificing side by rescuing the Tenth Doctor from Rassion before the Lord President could kill him. However it should be noted that the Master also wanted revenge since Rassilon had driven him insane as a child making it unclear if his motives were vengeance or concern for the Doctor's life; considering he warned the Doctor to step aside before attacking Rassilon it was probably a combination of both. (TV; The End of Time)

The Master was able to match the Doctor's intelligence and quick wit and was arguably the Doctor's most dangerous enemy, with the possible exception of Davros. The Tenth Doctor noted that despite his insanity the Master was a genius. However the Master was arrogant and this often caused his downfall as the Doctor was able to turn his overconfidence against him. (TV: Last of the Time Lords, The End of Time)

The Master is notable for his habit of coming back from the dead without needing to use regenerations. Much like Rassilon, he feared death and used a variety of methods to survive, regeneration being just one of them. Apart from the Doctor, he was the only Time Lord to escape from the Time War. Fleeing from the Time War also showed that he had a cowardly side of his personality since he had abandoned the Time Lords and Gallifrey to save his own life. (TV; Doctor Who Movie, The Sound of Drums, The End of Time)

Companions
Unlike the Doctor, the Master usually worked and travelled alone. On rare occasion, he was seen with companions. Examples included Ailla the Time Lord spy (PROSE: The Dark Path); 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); Chantho, a female assistant and companion to the Master in his Professor Yana identity (TV: Utopia); and Lucy Saxon, his wife, who 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)

In another universe
In one universe, the Master was a Magistrate for the High Council upon graduating the Time Lord Academy. Over time, his devotion to justice and discipline devolved into an obsession with order which marked the beginning of his descent into darkness (PROSE: The Infinity Doctors)

Character conception and development
When conceiving the character, the production team had originally considered the idea of the Doctor having a female arch-nemesis rather than male one (this idea was later revived with the creation of the Rani). Later, they thought of the Master as the evil half of a single personality. The Master's name was dreamed up as another counterpart to the Doctor's — like that of his enemy, "Master" is an academic title.

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 Delgado's accidental death. Over thirty years later, this idea would be reused in The End of Time with John Simm's incarnation of the Master sacrificing himself to save the Tenth Doctor from Rassilon.

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. This transitional form was used in The Keeper of Traken.

Is "Koschei" his true name?
The name "Koschei" has been developed in various novels. However, like the Doctor's name, the Master's actual moniker has never been revealed in performed Doctor Who.

Still, the name has a befitting Russian heritage. Koschei (rus. or Коще́й Бессме́ртный, "Koschei The Deathless") is an antagonist in Russian folklore. He is an immortal who hides his soul inside a needle, which is inside an egg, in a duck, inside a hare, in an iron chest which is buried under a tree on the island of Buyan. As long as his soul is safe, he cannot die.

Mistaken for other Time Lords
The Doctor Who Role Playing Game from the American gaming company FASA created a couple of misconceptions about the Master that are still occasionally heard in fan circles. The game postulated that the Master was the same Time Lord as the Monk from The Time Meddler and the War Chief from The War Games. FASA, however, are the only official licensees who have ever made this claim. In no way does any television script — nor any other narrative source — actually make this claim. Several books, including principally Divided Loyalties, explicitly contradict FASA's notions.

The Master is quite firmly his own Time Lord — and The Doctor Who Role Playing Game is not considered by this wiki to be a valid source of information.

How many Masters?
It has never been firmly established on screen how many incarnations of the Master have existed. The only number explicitly given by any narrative is that found in TV: The Deadly Assassin, where the Master is said to be near the end of his thirteenth and final life. In PROSE: Legacy of the Daleks, it's unambiguously established that Susan uses a combination of the Master's Tissue Compression Eliminator and her knowledge of the TARDIS to wreak devastating physical damage on the Delgado Master, resulting in the body seen in Assassin. Indeed, Legacy is, from the Master's point of view, a direct prequel to Assassin — one that shows us that the Assassin Master is merely the degenerated form of Delgado, not a wholly different incarnation.

Afterwards, in TV: The Keeper of Traken, the Master takes over Tremas' body and this Anthony Ainley version goes on to plague the Doctor until Survival. Since there is no actual regeneration, though, it's really still just a different form of the Delgado version.

There are no narratives whatsoever which unambiguously define the relationship between the Ainley Master and those that follow him, meaning that it's impossible to assign numbers to the Masters, in the same way that we would with incarnations of the Doctor.

That hasn't stopped at least one non-narrative source from trying, though. The 2010 edition of REF: Doctor Who: The Visual Dictionary indicates that the Master played by John Simm from TV: Utopia onwards was the "seventeenth Master". Jacobi would, according to this theory, be the sixteenth, Roberts the fifteenth, and Gordon Tipple the fourteenth — an incarnation otherwise played by Anthony Ainley. However, there's no narrative evidence to support any of the Visual Dictionary's claims.

Offscreen relationships
Although they played antagonists onscreen, 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 which led him to give up the role. (DOC: PanoptiCon 93, MM VHS 15)

Audio
Geoffrey Beevers is the main portrayer of the character in Big Finish audios. Sometimes, as in the The 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 has had the Tremas layer peeled away. Thus, in Dust Breeding and Master, he is once again the decayed version of the Delgado Master.

Additionally, Alex Macqueen portrayed the Master in the audio drama UNIT Dominion, although it is uncertain where in the Master's timeline this is set.

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 has 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. Harold Saxon in TV: The Sound of Drums and TV: Last of the Time Lords. 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 Yana was a Time Lord. "Mister Saxon", meanwhile, is an anagram of "Master No. Six" — though there's no clear evidence that this was intentional.

As a matter of coincidence, "Sam Tyler" — John Simm's Life on Mars character — is an anagram of "masterly".

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