User:BananaClownMan/Sandbox/The Master (UNIT enemy)

Fully embracing his darker nature after escaping a black hole he had been trapped in by the Second Doctor, the Master went on to fight various battles against the Third Doctor and UNIT during the Doctor's exile on Earth, even spending a short period also trapped on the planet until he retrieved his stolen dematerialisation circuit from the Doctor.

After the Doctor foiled his attempt to ally with the Dæmon Azal, the Master was arrested by UNIT Sergeant John Benton. With the government using him as a scapegoat to cover up recent extraterrestrial incursions, the Master was moved to various prisons until he was finally imprisoned on Fortress Island as the sole inmate, until he was able to orchestrate his escape with the aid of the Sea Devils.

After growing tired of his conflict with UNIT, the Master formed an allegiance with the Dalek Empire to start a war between Earth and Draconia. After his plan was foiled by the Doctor, the Master was either rendered into a wasted state by Susan Foreman or forced to regenerate after a battle with the Twelfth Doctor in a time locked dimension.

Post-regeneration
At some point, the Master regenerated into this incarnation, and visited the Scoundrels Club to recover from the regeneration in comfort. (PROSE: Dismemberment)

Start of darkness
Having begun calling himself "Koschei", the Master had a Time Lady named Ailla planted on him by the Celestial Intervention Agency to monitor his unstable obsession with order; Ailla 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 Galactic Federation. The temptation posed by the Darkheart device, capable of altering timelines without causing paradoxes or attracting the attention of various "higher beings", proved too much for Koschei, and the revelation that Ailla was a spy killed the last traces of good in him, and he became "the Master". After the Doctor trapped him in a black hole, the Master swore that he would take revenge. (PROSE: The Dark Path)

Early exploits
The Master penetrated Gallifrey, and gained access to the Matrix via a console in the old Capitol. This gave him a backdoor into the Matrix, which he used to collect classified information for his many devious schemes, (PROSE: The Quantum Archangel) including the Time Lords' files on the Doomsday Weapon (TV: Colony in Space) and the Sea Devils. (TV: The Sea Devils)

The Master then put his TARDIS in orbit of the homeworld of the Archons and made a deal with them that would result in the Archons acquiring the Doctor's TARDIS for themselves. Posing as a Professor Thascalos, the Master gave the Necronomicon to the Doctor's companion Jamie McCrimmon, so that Jamie would give the book to the Doctor and lure the TARDIS to the Archon homeworld. (PROSE: The Nameless City)

According to one Time Lord, before arriving on Earth, the Master was responsible for several interplanetary wars, but always managed to disappear before he could be brought to justice. Though the Time Lords managed to catch him, the Master escaped before his TARDIS "could be de-energised." (PROSE: Doctor Who and the Terror of the Autons)

Early times on Earth
The Master was imprisoned on Shada by the Time Lords at the time when the Doctor was exiled to Earth. However, the Time Lords decided to keep the Doctor busy whilst he was trapped on Earth by releasing the Master. (PROSE: Prisoners of the Sun)

The Master was present at the first Auton invasion of Earth, and heard about Channing's 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 called Stevens again during the Silurian attacks on Wenley Moor, informing Stevens that Edward Masters had been the first to die 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 UNIT article. He promptly hung up when Stevens mentioned C19 and the Glasshouse. (PROSE: Who Killed Kennedy)

Under the alias "Emil Keller", the Master captured a psychic parasite and trapped it within the Keller Machine, and spent many months establishing "Keller" and the machine's credentials. (TV: The Mind of Evil)

The Master 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, learnt of the failed Nestene invasion and the awakening of the Silurians. This inspired him to ally himself with the Nestene and to locate more Silurian colonies. (PROSE: Reconnaissance)

Becoming a threat
The Master appeared at the International Circus, with his TARDIS in the form of a horse box. He hypnotised the circus troupe and plastic factory manager Rex Farrel 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, and before the radio telescope could be used to bring the Nestene invasion force to Earth, the Doctor convinced the Master that the Nestenes would not distinguish between the Master and anyone else in their takeover, and the two worked together to fling the Nestenes back into space by "chang[ing] the polarity" whilst the radio telescope's transfer shift was still open. Afterwards, the Master fled. The Doctor, however, had already taken his dematerialisation circuit, 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. He used prisoners as a plan to hijack the Thunderbolt, a missile containing nerve gas and use it to destroy the World Peace Conference, which would trigger a nuclear war. The Doctor, with the help of Barnham, stopped the Master with the Keller Machine, and the Doctor reactivated the missile's abort mechanism. UNIT also destroyed the missile along with the Keller Machine, but the Doctor later discovered he had lost the Master's dematerialisation circuit in his altercation with the Master. Shortly after, the Master telephoned to let it be known that he had found the circuit and was free now to come and go as he pleased, while the Doctor had to remain in exile. (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 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)

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

Posing as a vicar named "Victor Magister" in the village of Devil's End (TV: The Dæmons; PROSE: Who Killed Kennedy) after murdering the old vicar, (PROSE: The Eight Doctors) the Master summoned the ancient Dæmon Azal, but he failed to understand the power and control that was necessary following summoning him. Following Azal's confrontation with Jo Grant's selflessness, Azal destroyed himself through Jo's illogical actions. The Master was captured by UNIT following a failed attempt to escape in the Doctor's car, Bessie. (TV: The Dæmons)

In custody
Prior to his trial, the Master was sent to Stangmoor Prison. During his captivity, an army of hypnotised salespeople stormed the facility and attempted to rescue him, but the ploy 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 used 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)

At his trial, the government used the Master as a scapegoat for all the alien attacks which had recently occurred. (PROSE: Who Killed Kennedy)

The Master was held at Aylesbury Grange Detention Centre. Demanding the Doctor visit him, he engaged the Doctor in conversation, insisting he had changed. However, the Doctor refused to believe him, and the Master reluctantly revealed that he had drawn the Doctor to the facility as part of an escape attempt and that the Doctor was speaking to a hologram. The Master nearly escaped but was stopped by UNIT soldiers accompanying the Doctor, who revealed he had been a hologram as well. (COMIC: The Man in the Ion Mask)

In another escape attempt, 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 ineffective to the Doctor's piloting. Before returning to his own body, he asked the Brigadier to move him to a new holding facility with a good view, and also encouraged Mike Yates to ask Jo Grant out on a date. (PROSE: The Switching)

While in custody, with the Doctor on 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, Ian and Barbara Chesterton to the alternate universe and encountering Koschei, the alternate version of himself. Koschei was imprisoned and tortured by order of the Leader of the Republic of Great Britain. The Master killed his other self, claiming it was an act of mercy. Before he was imprisoned by UNIT again, the Master hid his TARDIS back in the church crypt in Devil's End. (PROSE: The Face of the Enemy)

The Master was imprisoned inside a castle prison on Fortress Island as the only prisoner. The Master convinced his jailer, Colonel George Trenchard, to help him steal electronic parts from HMS Seaspite, telling Trenchard that this was intended as a lure for enemy agents. With these parts, the Master instead made contact with the reptilian Sea Devils, an aquatic species similar to the land-dwelling Silurians, and planned to cause a war between humans and Sea Devils, making the Sea Devils rulers of Earth again. Because the reactivation machinery of the Sea Devils' hibernation units deteriorated during millions of years of hibernation, the Master saw it necessary to construct a sonar device to awaken the remaining reptiles.

The Master captured the Doctor and forced him to help create this device, but to prevent the device from reactivating further Sea Devil bases and stop the war, the Doctor blew up the Sea Devil base by reversing the device's polarity, creating a massive reverse feedback. The Master escaped in a hovercraft when the officer guarding him, CPO Myers, was hypnotised and framed as the Master's corpse, (TV: The Sea Devils) and the Master returned to the church crypt in Devil's End to retrieve his TARDIS. (PROSE: The Eight Doctors)

At large again
Sometime after his escape, the Master took control of the Glasshouse, a facility for traumatised UNIT soldiers, taking particular control of Private Francis Cleary. 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)

On another occasion, the Master made a deal with the Odobenidans to help them invade Earth, but accidentally trapped both them and himself in a time loop whilst undertaking some temporal mechanics on their behalf. He was trapped in the time loop beneath Greece for months. The Doctor, sent to Greece by the Time Lords to deal with the time loop, released the Master and foiled his plan. (PROSE: The Seismologist's Story)

After being double-crossed by the Voords, (PROSE: The Quantum Archangel) the Master posed as "Professor Carl Thascalos" and constructed a machine known as TOMTIT at Cambridge's Newton Institute to summon the ancient chronovore Kronos, whom he wished to control. He hypnotised the institute's director, Dr Charles Percival, but accidentally killed him by releasing Kronos from the Crystal of Kronos. The Master summoned the Atlantean priest Krasis for instructions on how to control Kronos while meddling with the flow of time to obstruct the Doctor from getting in his way.

After knocking out Sergeant Benton, the Master retreated to his TARDIS, but the Doctor tried to trap him in a time lock using his own TARDIS, accidentally creating a space loop when both TARDISes were materialised within the other. When the TARDISes were separated during their negotiations, the Master ejected the Doctor into space, but the Doctor survived by using the telepathic circuit of his TARDIS to help Jo return him to safety.

The Master travelled to ancient Atlantis and failed to hypnotise King Dalios, who easily resisted his influence. Confronting the Doctor there, the Master tried to manipulate Queen Galleia into betraying her husband, since she had taken a romantic liking in his charm compared to Dalios' dull personality. Galleia, however, was enraged when the Master caused Dalios to die in the coup they staged in Atlantis. Before he was arrested, the Master commanded Krasis to use the Crystal of Kronos housed in Atlantis and brought forth Kronos, who destroyed the entire civilisation.

Fleeing Atlantis with Jo as his hostage, and with Kronos under his control, the Master was in a position to cast destruction unto the entire cosmos, however, the Doctor threatened to time ram the Master's TARDIS with his own, which would take everyone's lives in the process if he did not give up his plans for chaos. The Master did not believe the Doctor would earnestly carry out his warning because he knew endangering Jo's life was not an option for him. In response to the Doctor's hesitation, Jo tried to complete the time ram before the Master could release Kronos again. Instead, Kronos spared everyone from death, and captured the Master for the crime of trying to control it, but allowed him to go free at the request of the Doctor. (TV: The Time Monster)

The Master set up a talent show called Make a Star, based on the anagram "AKA MASTER", which he used to disrupt the timeline by making the contestants cover songs that weren't yet written. He intended to use the relatively minor disruption caused to allow him to take control of Earth, but this plan was foiled by the Third Doctor and Jo Grant. (PROSE: Hidden Talent)

The Master planned to release a fog in Tadcaster by using Sarkan mist-flowers to generate a fog that would engulf the Earth in a dense fog. Attempting to catch up with the Master, the Doctor commandeered a pier train that crashed into the Master and the mist-flowers, sending all of them into the ocean, where the flowers were destroyed and the Master disappeared. (COMIC: Fogbound)

Reappearing again, the Master took control of the Brigadier's mind and instructed him to kill the Doctor. However, the Brigadier attacked the Master, but he escaped, restoring the Brigadier to his senses. (PROSE: Smash Hit)

Distancing himself from UNIT
The Master travelled to the Land of Fiction, where he intended to steal an advanced piece of technology from the Land, and defeated Professor Moriarty, (COMIC: Character Assassin) and became involved in "a galactic fracas" relating to "a number of large tortoises". The Doctor and Jo put a stop to this scheme. (AUDIO: The Last Fairy Tale)

He attended Bonjaxx's birthday party at Maruthea. When a fight broke out, the Master was seen crouching to avoid the confrontation, evidently annoyed. (COMIC: Party Animals)

The Master 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)

For a short while, the Master adopted the identity of "Duke Dominus", a gangster on early 20th century Earth, but his plan was foiled by the Fourth Doctor without either realising the others' involvement. (PROSE: The Duke of Dominoes)

The Master travelled to a Sontaran-occupied planet and convinced several of the locals that he was a deity. This would form a new sect of proud, beard-toting column-worshipping Sontarans, which would decades later lead to the destruction of the entire planet by Sontaran command. The Master left decades before this, delighted simply by the idea of the chaos he had created. (COMIC: The Judas Goatee)

Having had enough of Earth, and having other plans to set in motion on Skaro, the Master employed the assistance of a being called Verdigris to impersonate him. (PROSE: Verdigris) On Skaro, the Master forged an 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)

Attacked by Susan Foreman
According to one account, the Master used files he had uncovered from the Daleks to go undercover 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 Tersurus, she used his TARDIS's telepathic circuits to attack him, forcing him out onto the planet's surface. She used his own Tissue Compression Eliminator against him while he was holding the Dalek's matter transmuter. The blast severely deformed and nearly killed him. Susan departed in his TARDIS; this brief materialisation, however, alerted the Time Lords to the Master's presence on Tersurus. Investigating the materialisation of an unauthorised TARDIS, the Time Lord Chancellor Goth arrived on Tersurus, where he found the Master in the form of a decaying animated corpse. (PROSE: Legacy of the Daleks)

Targeting the Collins family
According to another account, the Master decided to return to Earth after the affair with the Daleks and the Draconians and detected a massive discharge of temporal energy. He watched as the Twelfth Doctor's TARDIS exploded (COMIC: Doorway to Hell) in late 1972 after it was overloaded by its efforts to rewrite a mutated plague. (COMIC: The Pestilent Heart) The Master wrongly speculated this was the cause of the Doctor's third regeneration. (COMIC: Doorway to Hell) When the Doctor moved in with Jess Collins' family in Brixton and brought the TARDIS into the back garden to repair itself, (COMIC: Moving In) the Master plotted to use the artron energy given off by the regenerating TARDIS that now lay in the bodies of the Collins family to create a portal to a time locked dimension he learnt about in the Dalek databanks.

When the TARDIS had healed in early 1973, the Master utilised the efforts of Katya Dabrowski to bring the Collins family to an apartment in central London, while creating a diversion for the Doctor in Barking with glass mosquito creatures. Warning the Collins family that the Doctor was a dangerous and deceitful alien, the Master tricked them into being scanned for damage, when he actually used them to create a portal to the dimension which they were also sent through. The Master also stole the Doctor's TARDIS after killing his chess buddy Gabriel Gayle, and had the Doctor escorted from the Collins family's home to the Master's apartment. The Master linked the Doctor's TARDIS to his own, in order to aid the Doctor through the time lock, so he could be reunited with the Collins family. After he killed Jack Hayes to present himself being arrested, the Master had Katya accompany the Doctor to the other dimension.

Travelling to the locked dimension, the Master met Kiadine, a being who once split the chronon. The Time Lords locked him away for this, and he hated them for it ever since. He gave the Master his powers so that he would conquer Gallifrey on his behalf. His exposure to the chronon storm gave him god-like powers, and he began to fight with the Doctor for mastery of them. The Master fired one final attack as the Doctor stood arm in arm with the Collins family, and found that his attack had been repelled back at him with the same artron energy in the bodies of the Collins family that had brought the Master to the dimension. Though battered from the attack, the Master was able to escape in his TARDIS and regenerated while declaring his intent of revenge on the Doctor. (COMIC: Doorway to Hell)

Undated Events

 * 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)

Alternate timelines
When 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)

Parallel universes
In 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)

Personality
As the rival of the Third Doctor, the Master was often arrogant and impatient, taken to be rude towards all and showing no tolerance for stupidity. (TV: The Dæmons, The Sea Devils, The Time Monster, Frontier in Space) To sway others to his way of thinking, the Master acted as a suave and debonair gentleman, with a sardonic sense of humour. (TV: Terror of the Autons, The Time Monster) When his own survival was at stake, the Master would not hesitate to betray his allies to save himself. (TV: The Claws of Axos)

The Master was willing to play the long game, spinning a web of lies while maintaining several back-ups in his schemes. (TV: The Mind of Evil) He seemed to truly believe his delusions of grandeur, proclaiming that he and the Doctor could "reign benevolently," ending "war, suffering [and] disease," (TV: Colony in Space) and that, instead of "all this talk of democracy, freedom, [and] liberty", the world needed "strength, power and decision." (TV: The Dæmons) When the Doctor accused him of being paranoid, the Master stated that everyone was paranoid, he was just honest about his paranoia. (TV: The Time Monster)

The Master held himself in high-esteem, even believing himself immune to the mind parasite within the Keller Machine, when in truth, he was only able to resist its attack on him for a short time, and with great effort. (TV: The Mind of Evil) He also demonstrated a strong confidence in himself when he walked into the UNIT HQ on the edge of London without fear of capture, instead hypnotising a handful of UNIT personnel. (TV: The Claws of Axos)

This Master also had a juvenile side to him, making blithely sarcastic comments about an impending nuclear meltdown, (TV: The Claws of Axos) enjoying an episode of Clangers in his prison cell, (TV: The Sea Devils) and reading The War of the Worlds while trying to instigate a war between Earth and Draconia. (TV: Frontier in Space) He also had a sadistic side, taking particular pleasure in goading the Brigadier into attacking Axos when they both knew that it would put the Doctor and Jo Grant in danger. (TV: The Claws of Axos) He also took considerable delight in blackmailing the Doctor and Jo on Uxarieus. (TV: Colony in Space)

The Master often killed people, casually murdering those whom he could not control, (TV: Terror of the Autons) or who were standing in the way of an item he required. (TV: The Claws of Axos) He believed that those who died as a result of his schemes to be "necessary sacrifice[s]". (TV: The Sea Devils)

Unlike his following incarnations, this Master was rarely resentful, instead accepting defeat with only a slight annoyance, (TV: The Dæmons, Frontier in Space) though he once stated that destroying the Doctor's favourite species would "be a reward in itself". (TV: The Sea Devils) The Master also learned from his mistakes, placing an anti-intruder alarm beam in his TARDIS (TV: Colony in Space) after the Doctor stole his dematerialisation circuit. (TV: Terror of the Autons)

Being a haughty psychopath, he regarded most beings as his inferiors, but had a mutual respect for the Doctor as a worthy opponent and his near intellectual equal, (TV: Terror of the Autons, The Sea Devils) and even showed a certain respect to the Doctor's companions, even if he still considered them inferior. (TV: Frontier in Space) He often found himself unable to kill the Doctor, because that would rid him of the satisfaction of defeating him, (PROSE: Legacy of the Daleks) and would only resort to killing the Doctor if he viewed him as an unmovable obstacle in his plans, (TV: Terror of the Autons) considering his quarrel with the Doctor to be something of a game, though he was willing to risk the Doctor's life on the Keller Machine to satisfy his curiosity. (TV: The Mind of Evil) However, the Master was not above working alongside the Doctor when necessary, (TV: The Claws of Axos) and even offered to rule the universe with him. (TV: Colony in Space)

While in Atlantis, the Master formed a relationship of sorts with Queen Galleia, remarking that she was beautiful and promising her power. Both Galleia and Lakis commented that the Master had "the bearing of a God". (TV: The Time Monster)

After an attack he made on the Twelfth Doctor was sent back at him, the Master, claiming he would get his revenge on the Doctor, proudly welcomed his regeneration, declaring that death was meaningless to him and that "all life [would] obey [him]". (COMIC: Doorway to Hell)

Habits and quirks
During this incarnation, the Master would often smoke a cigar. (TV: The Mind of Evil, The Time Monster)

Skills
A master manipulator, the Master knew how to use others' greed and sense of duty as bargaining tools in his schemes, (TV: The Claws of Axos, The Sea Devils) and how to use his authority as an adjudicator to manipulate and influence the human factions and their competing aspirations on Uxarieus. (TV: Colony in Space)

The Master was also stronger than he appeared, as he was able to physically overpower Luigi Rossini, (TV: Terror of the Autons) Harry Mailer, (TV: The Mind of Evil) Smedley, (TV: The Sea Devils) and John Benton. (TV: The Time Monster) He was also able to make a small jump onto a moving lorry from a bridge, and then swing down to the driver's cab to hypnotise the driver. (TV: The Claws of Axos)

Appearance and clothing
The Master resembled a mature, elegant man, with a swarthy complexion, brown eyes, and mild streaks of grey in his hair. He had a goatee beard, which also had white skunk stripes. He generally wore a black Cardin-Nehru jacket, with dark trousers, black leather boots and gloves, and a white cuff-linked shirt. (TV: Terror of the Autons) On occasion, he would wear a suit, with either an orange, grey or blue tie. (TV: Terror of the Autons, The Mind of Evil, The Time Monster)

While imprisoned on Fortress Island, the Master wore a black cape over a white turtle-neck jumper, with black trousers, but switched these for a naval officer's uniform while secretly infiltrating HMS Seaspite. During his return and subsequent escape from Fortress Island, he changed back into his black Nehru jacket and trousers. (TV: The Sea Devils)

Character conception and development
Barry Letts and Terrance Dicks often discussed that the relationship between the Third Doctor and the Brigadier is similar to Sherlock Holmes and Dr Watson. Inevitably, this led them to a question: where is Moriarty? They envisioned a counterpart of the Doctor, a character that became the Master. (DOC: The Doctor's Moriarty)

In a way, the Doctor himself was the model of the Master. At first, the Doctor Who production team 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. But this does not mean that the Master has a lesser academic degree than the Doctor, as in a master's degree. Both being Time Lords, they have the same level of education and are graduates of the Time Lord Academy. In The Sound of Drums, we learn that both had chosen their names because of what they meant — the Doctor as a healer of wrongs, the Master because of his desire for conquest and dominance.

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 accidental 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 sacrificing himself to save the Tenth Doctor from Rassilon.

Is "Koschei" his true name?
The 1997 novel The Dark Path shows the Second Doctor in one of his first encounters with the Master since leaving Gallifrey. Throughout the story, the Master is only called by the pseudonym "Koschei". In Russian folklore, Koschei (rus. or Коще́й Бессме́ртный, "Koschei The Deathless") is a villain who hides his soul in an obscure location under many layers of protection so that he can never die.

Though the Second Doctor does not recognise Koschei by that name in The Dark Path, later stories like Divided Loyalties and The Face of the Enemy reuse the name in ways that suggest it is the true or original name of the Master. The 2018 short story Lords and Masters casts this theory into doubt, however, as Missy states that her real name contains thirty-two letters, though it is possible that "Koshei" is a diminutive, or even a first or last name which, added up with the other, amounts to thirty-two.

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)