Rassilon

Rassilon was, alongside Omega and the Other, one of the founders of Time Lord civilisation. In their own time, Rassilon was chiefly an engineer and architect, but later Time Lord society would hail them as the first Time Lord and the single greatest figure of Gallifreyan history. However, some Time Lords contended that Rassilon was a corrupt megalomaniac who tried to murder their friend Omega and stole their invention.

Among the titles they acquired during their life were the "Conquerer of Yssgaroth", the "Overpriest of Dronid", the "First Earl of Prydon", the "Patris of the Vortex", and the "Ravager of the Void".

After his physical death, Rassilon stayed active in the Matrix, ruling Gallifey from the shadows as the leader of the Matrix Lords, and manipulated the Doctor into performing many missions for him. During the Last Great Time War, he was resurrected from the Matrix to lead the Time Lords, becoming "Rassilon the Resurrected", and he ultimately tried to find ways to break the time lock and escape the War. After the Doctor saved Gallifrey, and the Time Lords returned Gallifrey to N-Space from its pocket universe, Rassilon was overthrown and banished in a coup led by the Twelfth Doctor, whom Rassilon had kept trapped inside the Doctor's confession dial for four and a half billion years. Desiring revenge, Rassilon allied with a colony of Cybermen at the end of the universe, being converted into the Cyber-President, and created an alternate timeline where the Cybermen conquered all of history. However, Rassilon and the Twelfth Doctor ultimately erased this timeline from existence after the Cybermen betrayed the former, once again leaving Rassilon alone at the end of the universe.

Early life
Rassilon was born the child of a suet shredder. (PROSE: Cat's Cradle: Time's Crucible) A mere Gallifreyan, they had two hearts and other such organs which guaranteed them a lifetime of "300 years or so", but did not yet possess regeneration. Their original body had dark hair. According to one account, Rassilon was initially a boy, (PROSE: The Legacy of Gallifrey) but another account claimed that Rassilon's first incarnation was a dark-skinned female. (COMIC: Monstrous Beauty) Omega later claimed that a timeline where Rassilon was both a woman and in love with him was one of several possible timelines all culminating in Omega's unwilling sacrifice. (PROSE: The Infinity Doctors)

According to Coordinator Engin, Rassilon was initially chiefly regarded as an engineer and architect. (TV: The Deadly Assassin) The Scrolls of Gallifrey named them and Omega as solar engineers, one of a small number of Gallifreyans who continued to think of the future of their planet, rather than entirely surrender to the beguiling prospect of interstellar travel and of making themselves into gods for the later species. Rassilon lusted to see more than a mortal man could in a lifetime, with their first goal being the creation of immortality, until Omega convinced them that this was unachievable and that the both of them should instead turn their minds to the creation of time travel. (PROSE: The Legacy of Gallifrey) A secret account buried deep in the Matrix revealed immortality, which came in the form of regeneration, was extracted from the Timeless Child. (TV: The Timeless Children)

The Vampire Wars
During the anchoring of the thread, Rassilon accidentally unleashed the Great Vampires into the universe, (PROSE: Interference: Shock Tactic, The Book of the War) beginning the Eternal War. (PROSE: The Pit)

Rassilon was a Commander during the war. At one point, she led forces based on a shadow planetoid. The Ninth Doctor and Rose Tyler arrived on the planetoid and were captured by Rassilon's forces. She was intrigued by them, but they escaped during an attack from Cucurbites. The Doctor returned to the Gallifreyans and helped them stop the Curcurbites, after which Rassilon interrogated him at gunpoint. He conspired with Androkan to steal her ship however, jettisoning her and her guards. However, Rassilon had left a tracker aboard and called for reinforcements to pursue them to a coffin ship. The Doctor ejected her ship and the coffin ship fled, with the Gallifreyans now unable to trace it, leading Rassilon to swear revenge on him. (COMIC: Monstrous Beauty)

When Rassilon returned from the Eternal War, (PROSE: The Pit) he led the overthrow of the matriarchal society of the Pythia with his Neo-Technologists. (PROSE: Cat's Cradle: Time's Crucible) Indeed, according to one of Omega's unreliable memories, development of his and Rassilon's time travel program only came about after a revolution. On the day the revolution was to break out, while Omega and him journeyed to the top of a mountain to overlook a coming fire that would consume the Capitol, the two debated Omega's nickname. When Omega noticed the revolution below, he begged for Rassilon to stop the bloodshed, only for Rassilon to reason that, with the Inquisitors rounding up all the "moaning minis" who did not believe in the theories the two offered, they would be able to move into power and finally achieve all they sought to. Afterward, Rassilon indeed became a politican, whereas Omega remained a scientist. (AUDIO: Omega)

Creating the Eye of Harmony
Rassilon and Omega created the living metal validium, (TV: Silver Nemesis) and, with the help of the Other, also created the Hand of Omega, a stellar manipulator. (PROSE: Remembrance of the Daleks), while posing as the Doctor, later claimed that Rassilon, as well as the "forefather of all Time Lords", had been his mentor; (PROSE: The Novel of the Film) the Doctor, by more than one account, was the reincarnation of the Other. (PROSE: Lungbarrow)

The Eleventh Doctor described Rassilon as being "Omega's boss". (COMIC: The Lost Dimension) Together, Rassilon and Omega planned to use the Hand to induce a supernova in the star Qqaba. The energy released would enable the Gallifreyans to travel through time. (COMIC: Star Death) The Gallifreyan Council was initially reluctant to finance the project, in which they had little interest, with Council Leader Tussan attempting to humiliate Rassilon by rhetorically asking his cat what the Council should do in the matter. When the cat answered that Gallifrey should back Rassilon and Omega's temporal experiments, the Council reluctantly agreed. (PROSE: The Legacy of Gallifrey)

The creation of the Time Lords' time travel's power source caused the apparent death of Omega as he fell into the black hole, (TV: The Three Doctors) while Rassilon comfortably sat at the control console of the mast on Gallifrey, which would receive the power Omega helped channel. After Omega made the "ultimate sacrifice," it was Rassilon who received all of the credit, despite his comparatively minor role in the actual achievement. (PROSE: The Legacy of Gallifrey)

One account theorised that Rassilon, jealous of Omega's popularity on Gallifrey, had prompted Omega's assistant, Vandekirian, to betray him at the last second. (AUDIO: Omega) Another account stated that Rassilon instead had personally deactivated Omega's protective forcefield remotely seconds before the star's detonation. (PROSE: The Scrolls of Rassilon) This betrayal was hidden from the Gallifreyans, as the Fourth Doctor believed that Omega's death was caused by the interference of a Black Sun agent named Fenris the Hellbringer, (COMIC: Star Death) though the Fifth and Eleventh Doctors knew of the theory that opined that Rassilon had had Omega's assistant sabotage the experiment. (AUDIO: Omega, COMIC: The Lost Dimension) Rassilon publicly wept for the loss of Omega, (PROSE: Lungbarrow) and banished Fenris into the Zone of No Return to avenge Omega. (COMIC: Star Death)

Furthermore, by one account, Omega had forged Vandekirian's hand into a stellar manipulator dubbed by Rassilon "the Hand of Omega"; Rassilon did so to further win the love of his people, having elected to publicly celebrate his lost friend, whereas naming the device after the disliked Vandekirian would not have generated support. (AUDIO: Omega) Improving on Omega's mathematics to succeed in creating a supernova, (PROSE: A Brief History of Time Lords) Rassilon had the mast renamed the Eye of Harmony and buried beneath he floor of the Capitol, locked away with a Great Key. (PROSE: The Legacy of Gallifrey) There it lay, beneath the Panopticon, for untold eons. (TV: The Deadly Assassin)

According to The Book of the Old Time, however, Rassilon had journeyed with a great fleet to locate the already-existing singularity of the Eye of Harmony and bring it back to Gallifrey. (TV: The Deadly Assassin) While one late Time Lord historian thought this to be no more than propaganda, (PROSE: A Brief History of Time Lords) the Eleventh Doctor told Amy Pond that the Eye of Time was originally the singularity at the heart of the Big Bang when explaining its nature to her. (GAME: City of the Daleks) The Book of the Old Time actually contained sacred star-charts which had been stolen by the Time Lords from Voyager, a mysterious Lord of Life; the Doctor speculated that, "aeons ago", Voyager had sailed his Death-ship through the dreams of Rassilon. (COMIC: Voyager) It was also said that, to create the Eye, Rassilon had reached into the life-giving explosion of the Big Bang and extracted the core, "stabilising its creative potential". (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)

Spinning the Web of Time
Over the years, the Eye of Harmony's power grew on its own, and Rassilon eventually descended once again beneath the Capitol to study its new properties. Comprehending the elemental forces at play in the heart of the Eye, Rassilon managed to refine them, setting them in a "perpetually dynamic equation" with the mass of the planet itself. The Eye would act as a power source for all of Gallifrey, and as a cornerstone in Time. (PROSE: The Legacy of Gallifrey)

Rassilon used his new technology to map out all of creation, building the Web of Time and purging reality of all irrationality. This anchoring of the thread created history in Gallifrey's image, and with it, Rassilon and his people truly became lords of all time and space. (PROSE: Christmas on a Rational Planet, The Book of the War)

Rassilon's first presidency
Jealous of his power over the Eye of Harmony, Tussan's all-Arcalian Gallifreyan Council attempted to force an aging Rassilon into retirement, offering him a pension and a honorary, but powerless, seat on the opposition council in exchange for the Great Key and Sash necessary to access the Eye. Outraged, Rassilon tore the Sash apart, putting the Eye out of anyone's direct reach but his own. Tussan ordered Rassilon taken away by the Chancellery Guard to be punished, but, before they could do so, Rassilon collapsed, dying from the temporal radiation of the Eye's elemental forces. However, his prolonged exposure to the Eye had granted him the gift of regeneration, and Rassilon awoke from death in a younger, fair-haired body. Using the fame and mystique his regeneration had awarded him among the Gallifreyans, Rassilon deposed Tussan's Gallifreyan Council. (PROSE: The Legacy of Gallifrey)

According to a different account, the President at the time of the Vampire War was Pandak, who Rassilon overthrew in a coup; (PROSE: The Scrolls of Rassilon) the Eremites believed the first official Lord President had been Urizen. (PROSE: The Book of the War)

Yet another alleged that Rassilon first earned himself a seat on the High Council by advocating for the abolition of the Games in the Death Zone and the banning of the Time Scoop, and only later became President. (PROSE: A Brief History of Time Lords)

In the early days of his rule, Rassilon imposed higher taxes on the Gallifreyan people. (PROSE: The Scrolls of Rassilon) He also created the transduction barrier that protected Gallifrey from outsiders at the dawn of the Rassilon Era. (PROSE: The Scrolls of Rassilon, A Brief History of Time Lords) Around this time, he was approached by the Stranger, who told him of Gallifrey's future and pleaded with him to change established events to make the Time Lords less powerful and selfish than they would become. (PROSE: The Scrolls of Rassilon)

End of the Vampire War
As President, Rassilon left the safety of the main fleet to investigate rumours of a vampire hive. His ship was attacked by the bird-like Ra'ra'vis, and he became their prisoner. Rassilon was asked to perform time experiments for them, in order to advance their technology. He was saved by Jorus, a Vogan. Rassilon gave Jorus his seal and told the Vogan the power of the Time Lords. The seal of Rassilon then became a key piece of iconography on Voga. (PROSE: Jorus and the Voganauts)

After regenerating into a body that was full-bearded, Lord President Rassilon was told by General Skellis that his tactic of using dispersal as a way of eliminating any Great Vampire they found actually caused the Vampires to spread across the universe, and told him that penetrating their heart was a much simpler way of killing them. Rassilon then employed Bowships to hunt them down. (PROSE: The Multi-Faceted War) The campaign was largely successful, but the King Vampire was not found. (TV: State of Decay, PROSE: Interference: Shock Tactic) After searching for the King in vain for years, President Rassilon declared the war over. (PROSE: The Multi-Faceted War)

After the war, Rassilon wrote the Record of Rassilon, giving a history of the war and instructions to all Time Lords to kill the King Vampire if ever they came across him. (TV: State of Decay) The record was written into every TARDIS. (PROSE: The Multi-Faceted War)

According to Faction Paradox-influenced transmissions from Anathema, during the war, Rassilon had been exposed to vampire biodata in what he described as inoculation. (PROSE: Interference: Shock Tactic) The Cult of Rassilon the Vampire on Gallifrey believed that this caused him to become a vampire. (PROSE: Goth Opera)

Foundation of Time Lord society
As the Time Lords banished the last fragment of impossibility from the universe, Rassilon said: "Now, see what we have created, we have built a world of reason triumphant. And it is good." (PROSE: Christmas on a Rational Planet ) With his Five Principles, Rassilon led Gallifrey into a more enlightened age, bringing about a new social order. Among these changes, slavery was abolished. (AUDIO: Forever)

According to the histories that Rassilon himself wrote, the Pythia retaliated by cursing Gallifreyans to be sterile. (PROSE: Cat's Cradle: Time's Crucible) However, the sterility may have, in reality, been a result of the anchoring of the thread. (PROSE: The Book of the War) Rassilon solved the problem by creating the Great Houses and building the Looms that artificially birthed new Time Lords. (PROSE: Cat's Cradle: Time's Crucible)

After fleeing the Homeworld during the First Diaspora following the anchoring of the thread, the Eremites instead remembered the first President of the Time Lords, responsible for the sterility of Time Lord civilisation, as being Urizen the Architect, whom they would later caricature as a blind old man measuring his own dung with a set of dividers. (PROSE: The Book of the War)

As he ordered the new political system of Gallifrey, with himself as Lord President of a High Council, Rassilon decided to create a new, immortal aristocracy: a hundred men and women of each chapter were permitted to stand in front of the Eye of Harmony, granting them the gift of regeneration and properly making them into Time Lords. The cat who had helped authorise Rassilon's experiments betrayed Tussan and joined his side. (PROSE: The Legacy of Gallifrey)

According to other accounts, Rassilon worked with a biologist named Thremix, who had created a virus that he speculated would grant the Gallifreyans immortality. Rassilon ordered the release of the virus, which wiped out a large proportion of the Gallifreyan population, and gave the remainder the ability of full-bodily regeneration. (PROSE: The Scrolls of Rassilon) The Valeyard claimed that Rassilon intentionally implemented a flaw in regeneration, meaning that Time Lords could only do so twelve times, so he alone could have true immortality, (AUDIO: Trial of the Valeyard) whereas the account which showed regeneration flowing from the Eye of Harmony also stated that Rassilon's original regeneration cycle was also limited to twelve renewals. (PROSE: The Legacy of Gallifrey)

A secret account buried deep in the Matrix was found by however, which stated that these commonly-cited origins of regeneration were mere propaganda to conceal the fact that the secret had actually been extracted before the discovery of time travel and the foundation of Time Lord society, taken from an innocent child found on an off-world expedition by the Shobogan explorer Tecteun. It was in fact Tecteun who had proposed the idea of regeneration cycles, gene splicing the ability to regenerate into future generations of Shobogans, who would later become synonymous with Gallifreyans and rename themselves Time Lords. The truth was hidden under a visual filter, telling the story of an immortal Irish policeman called Brendan. (TV: The Timeless Children)

At war with the universe
Rassilon led the Fledgling Empires against the Racnoss in the Racnoss Wars, and ultimately won the conflict. (PROSE: Pandoric's Box)

Not long after Omega's death, Rassilon led the Time Lords against the Nestenes, managing to contain their forces in the Illia galaxy. He personally persuaded scientist Roppen to reconfigure the Eye of Discord into a new device, one which he dubbed the "Galaxy Eater". After the device's interface gave him a brief encounter with several of his future selves, Rassilon activated the device and destroyed the Nestenes in the Illia galaxy. He then placed the device in the Omega Arsenal for safe keeping. (PROSE: Pandoric's Box)

Rassilon led the Time Lords in the Millennium War, against the Mad Mind of Bophemeral. His memory of the event was erased, as happened to all others who took part in the war. (PROSE: The Quantum Archangel)

Rassilon created the Alliance of Races (COMIC: Gangland) in a war against the Hyperions. (COMIC: Terrorformer) After the Hyperions were defeated, Rassilon and the Alliance of Races embarked on another purge of races that were a threat to universal harmony. One such enemy was Count D'if and his Cybock Imperium. Rassilon challenged D'if to a game of Rassilon's roulette using the Time-Gun of Rassilon, which was programmed not to fire on him. D'if lost and he was wiped from existence. The Twelfth Doctor claimed that it was that moment that the Gallifreyans first began to fear their president. (COMIC: Gangland)

Temporal progress
Rassilon invented TARDISes after a war with the Archons. (AUDIO: The Next Life; PROSE: The Nameless City) In developing the TARDISes, Rassilon had ordered all time sensitives brought to him. When he saw the Eleventh Doctor, who had, unknown to Rassilon, accidently arrived in the past, tame a Type 1 TARDIS, Rassilon ordered him brought to him. After talking with the Doctor, Rassilon, having some inexplicable familiarity with the Doctor, used him to fast track the development of the TARDISes, while surreptitiously barring him from getting the fluid links that he needed. When the Type 1s were taken on their test flights, the Doctor was assigned the vessel that he had initially calmed down, but, much to Rassilon's horror, the TARDIS had a leftover dimensional bubble and was considered lost after the dematerialisation. When the Doctor's companion, Alice Obiefune, who had been posing as his wife, came rushing in, Rassilon offered his personal apologies. (COMIC: The Lost Dimension)

To enable Time Lords to travel through time without ill effects, Rassilon created a genetic link called the Rassilon Imprimatur. (PROSE: Interference: Shock Tatic)

Rassilon created a living weapon known as the Pariah, which he used for missions throughout time and space. Rassilon gave the Pariah independent thought, but this proved to be a mistake, as the Pariah developed a mind of its own and rebelled against him. Rassilon banished the Pariah from Gallifrey, then created Shayde, a more evolved version of the Pariah incapable of independent thought. The Pariah would cause the creation of the Threshold. (COMIC: Wormwood)

Using temporal technology, Rassilon studied the future. He learned of the Divergence, a race which would eclipse his within ten thousand millennia. Fearing this future, he created a self-replicating, biogenic molecule which he sent back in time to seed all habitable planets in Gallifrey's galaxy. This ensured all intelligent life evolved in the form of the Gallifreyans. He trapped the Divergence in their own timeline, which Rassilon sealed into a time loop. (AUDIO: Zagreus)

Abdication
According to Postar, Rassilon, confident in his power, created the Death Zone, a region of Gallifrey devoted to "the Game of Rassilon" (PROSE: The Legacy of Gallifrey) which had previously been the site of bloody games involving mere Gallifreyans. (PROSE: The Scrolls of Rassilon) The Dark Tower he had built in its centre had a link to the Eye of Harmony through which it could Time Scoop individuals from all over time and space, who would be made to fight to the death for the privilege of being returned home. Many tried to get him to stop the games, but only after a group of Cybermen nearly destroyed the Dark Tower did Cardinal Pandad succeed in persuading him of the foolishness of his actions, as, had the Cybermen succeeded in destroying the Tower, they might have released the power of the Eye of Harmony, and, through exposure to it, gained the same immortality and temporal abilities as the Time Lords.

After decreeing the three fundamental Laws of Time to prevent any of his successors failing as he had, Rassilon, now in his thirteenth incarnation, abdicated from the Presidency in favour of Pandad, further shaping the political system of Gallifrey by creating the positions of Chancellor and Castellan. The former individual would be told of the location of the Great Key to the Eye of Harmony, but on the condition that they never become Lord President. (PROSE: The Legacy of Gallifrey)

However, all of this contradicted the research of another Time Lord historian, who claimed that the Game and Death Zone predated Rassilon's Presidency — and, indeed, that he had made his name, and earned his seat on the High Council, by campaigning for its abolition. (PROSE: A Brief History of Time Lords)

Supposed death and survival
Rassilon died whilst in his thirteenth incarnation, (PROSE: Pandoric's Box) discovering to his dismay that the regeneration cycles granted by the Eye of Harmony only allowed for twelve renewals. Gaining the trust of Chancellor Azmeal, Rassilon, once more desperate to extend his life and power, created the Matrix, in which the minds and memories of dying Time Lords would be recorded. Though Azmeal presented the project to the High Council as a "psychic history book", the truth was that the disembodied Time Lords would remain conscious within the Matrix, with Rassilon first among them as the leader of the Matrix Lords. (PROSE: The Legacy of Gallifrey) Before his death, Rassilon prepared his tomb to test those who sought the gift of immortality, (PROSE: Pandoric's Box) and copied his mind into the Matrix. (AUDIO: Zagreus)

Many rumours surrounded Rassilon's death (or lack thereof). One stated that the Time Lords had revolted and imprisoned him in the Dark Tower in the Death Zone. (TV: The Five Doctors) Over the millions of years after the end of Rassilon's Presidency, he came to be revered on Gallifrey. Time Lord history credited Rassilon with creating the traditions of their society; for instance, after Rassilon had a nightmarish vision of a dictatorial, imperialistic Gallifrey, he was said to have created the principles of non-intervention. (COMIC: The Final Chapter) Secret societies on Gallifrey worshipped Rassilon as a god. (AUDIO: Intervention Earth)

Within the Matrix
After his physical death, Rassilon stayed active in the Matrix. (COMIC: The Tides of Time)

First reborn incarnation
During the early days of Last Great Time War, Rassilon was the first Time Lord to be resurrected by Project Revenant, in order to lead the his people against the Daleks. (AUDIO: Desperate Measures)

Second reborn incarnation
After being injured by the Sicari, Rassilon had his regeneration broadcast across Gallifrey, increasing his influence over the Time Lords (AUDIO: Assassins) and continuing his reign in Rassilon. (AUDIO: Deception)

Last Time War incarnation
By the end of the Time War, one of Rassilon's proposed last resorts to win the war was the implementation of the Ultimate Sanction. (TV: The End of Time)

After the Time War
When the Twelfth Doctor returned to Gallifrey after Time War, he deposed Rassilon and banished him from the planet. (TV: Hell Bent)

Skills and abilities
By the time of the foundation of the Time Lords' civilisation, Rassilon already proved to be able to stop a Gallifreyan fleet from falling into a black hole; moreover, he could spring bolts of power arc from his fingertips, a power called electro-direction. (COMIC: Star Death)

During the final days of the Last Great Time War, with the apparent help of the Gauntlet of Rassilon, he was able to provoke the molecular dispersal of another Time Lord and to revert the effects of an Immortality Gate on a planetary scale, just with a gesture ending the Master's control and was also capable of developing various scenarios and outcomes and his scheme was only foiled by the Doctor's timely intervention. (TV: The End of Time)

During his alliance with the Cybermen, Rassilon proved able to siphon away power from every TARDIS in existence by manipulating the Eye of Harmony. (COMIC: Supremacy of the Cybermen)

Artefacts
Many important Gallifreyan artefacts bore their name, with Rassilon imbuing the items with powers to protect their legacy and enhance Rassilon's own mystique. (PROSE: A Brief History of Time Lords)

These included the Sash of Rassilon, the Rod of Rassilon, (TV: The Deadly Assassin) the Coronet of Rassilon, the Harp of Rassilon, (TV: The Five Doctors) the Crown of Rassilon, (TV: The Invasion of Time) and the Seal of Rassilon, a symbol used as a mark of Time Lord authority which appeared as a motif in many Time Lord designs. (TV: The Deadly Assassin, The Five Doctors) These were stored in the Capitol and, save for the supremely powerful Great Key, which at one stage found its way into the hand of Cardinal Borusa, were made available to the Lord President of the Time Lords. (TV: The Invasion of Time)

The Black Scrolls of Rassilon, also later obtained by Borusa, contained forbidden, arcane secrets. The fabled Ring of Rassilon, however, capable of conferring a form of immortality upon the wearer, resided in the Tomb of Rassilon in the Dark Tower located in the Death Zone. (TV: The Five Doctors)

These artifacts, like many institutions in Time Lord society, were named "of Rassilon", in such number and with such unfailing consistency that the Eighth Doctor once reflected that Joanna Harris "couldn't imagine how much [he'd] had it in here with the This, That and the Other of Rassilon". (PROSE: Vampire Science)

Personality
Rassilon was a charismatic leader who was capable of inspiring their people. The General himself stated that, while Rassilon eventually became corrupt, he was once "a good man". (TV: Hell Bent) Indeed, Rassilon was initially a man who hated corruption and was good at detecting it, (TV: The Five Doctors) but became corrupt himself following his resurrection for the Last Great Time War. (PROSE: A Brief History of Time Lords) Nonetheless, according to one of Omega's memories, Rassilon was very dismissive towards him, despite calling Omega a friend and letting him call him "Rass". The memory also revealed he believed anyone who opposed his and Omega's ideas was a fool who did not deserve political power. (AUDIO: Omega)

During the early history of the Time Lords, Rassilon led the revolution against the last Pythia, (PROSE: Cat's Cradle: Time's Crucible) overthrew President Pandak, (PROSE: The Scrolls of Rassilon) and instituted changes to deal with the problems of the Empire, such as ordering the creation of genetic looms to permit the Gallifreyan race to reproduce, (PROSE: Cat's Cradle: Time's Crucible) creating the transduction barrier, (PROSE: The Scrolls of Rassilon) and completely ended "the Games" in the Death Zone (TV: The Five Doctors) after a period of using alien warriors instead of Gallifreyans. (PROSE: The Scrolls of Rassilon)

Rassilon and the Time Lords also created the Web of Time to purge the universe of irrationality. (PROSE: Christmas on a Rational Planet) During the development of the Type 1 TARDISes, Rassilon projected an air of affability, asking to be called "Rass" by his closest friends and openly complementing the Eleventh Doctor's genius while eagerly pushing his species to venture beyond new horizons. Despite this, Alice Obiefune noted that Rassilon remained cunning enough to prevent the Doctor from leaving the Capitol, suspecting that Rassilon knew that the Doctor was from the future. When the Doctor was thought lost however, Rassilon appeared genuinely horrified and offered Alice his personal apologies for the tragedy. (COMIC: The Lost Dimension)

Controversially, Rassilon ordered the release of a virus that wiped out a large proportion of the Gallifreyan population, while allowing the survivors to regenerate. (PROSE: The Scrolls of Rassilon) He also discovered how to become immortal without having to use regenerations to survive, but believed that the secret was too dangerous to share, and thus kept it to himself, (TV: The Five Doctors) and instituted the non-interference policy after dreaming of a future Time Lord empire that used its power to suppress the weak of the universe. (COMIC: The Final Chapter)

Rassilon was intimidating and unforgiving, but was also a hero to many Gallifreyans, (AUDIO: Zagreus) with the Second Doctor calling him "the greatest single figure in Time Lord history", (TV: The Five Doctors) though the Twelfth Doctor recalled how the Gallifreyans began to fear Rassilon after he beat Count D'if at Rassilon's roulette. (COMIC: Gangland) However, Rassilon's wisdom in recognising the curse of immortality and their opposition to the corrupting influence of power (TV: The Five Doctors) did not prevent them from becoming corrupted by power themselves, such as with their prejudice against Vampires, (AUDIO: Zagreus) and becoming increasingly obsessed with avoiding death during the Last Great Time War against the Daleks, (TV: The End of Time) a desire they'd harboured in one way or another their childhood. (PROSE: The Legacy of Gallifrey)

After the loss of Omega, Rassilon wept for him, with the Other musing that Rassilon's later actions were born out of love. (PROSE: Lungbarrow) However, some believed Rassilon to actually be behind the plot to murder Omega, (AUDIO: Omega) despite the evidence against the assassin Fenris, whom Rassilon banished into the Zone of No Return to avenge Omega, (COMIC: Star Death) while another account had it that Rassilon had been directly responsible for Omega's protective forcefield failing. (PROSE: The Scrolls of Rassilon)

After punishing Borusa for attempting to claim immortality, Rassilon offered immortality to the First, Second, Third and Fifth Doctors, and admitted that they had "chosen wisely" after they declined, and sent them back to where they belonged afterwards, (TV: The Five Doctors) even giving the First Doctor complete control of his TARDIS to allow him to attend to unfinished business before his regeneration as a show of gratitude. (PROSE: The Witch Hunters)

Rassilon was also manipulative, trying to trick the Eighth Doctor into destroying the Divergence in the belief that they were too different to live, (AUDIO: Neverland, Zagreus) and using as a link between Gallifrey and the rest of the Universe which allowed him to temporarily free Gallifrey from the time lock. (TV: The End of Time)

By the end of the Time War, Rassilon had become ruthless, power-hungry and insane, being willing to destroy the whole of creation rather than accept the end of the Time Lords. He planned to change himself and the Time Lords into beings of pure consciousness, free of physical bodies and the ravages of time, in his Ultimate Sanction. Rassilon had also grown in his pettiness, vaporising the Partisan for speaking against his desire to continue the Time War, and taunting the Tenth Doctor with how "the final act of [his] life [would be] murder" after a failed attempt to fool the Doctor into an alliance with him. Even as he was dragged back into the war, Rassilon made one last hateful attempt to kill the Doctor. (TV: The End of Time)

Following the end of the Time War, Rassilon retained his arrogance, believing himself superior to others simply for being Lord President, and showed no remorse for locking the Twelfth Doctor in his confession dial to get the information he wanted. He also showed his sadistic side by gloating how he could remove the Doctor's regenerations one at a time. (TV: Hell Bent) After his banishment, Rassilon was driven to teaming up with the Cybermen to survive and reclaim Gallifrey, unhinged to the point of casting off the "Time Lord purity" he'd championed throughout his reign. His ego grew ever more, so much so that he redecorated the Panopticon with statues of his former incarnations, openly proclaiming that the Time Lords "[belonged] to [him]". After being betrayed by his allies however, Rassilon gained a sense of shame and humility, horrified at how he'd given the Cybermen so much power and finally making peace with the Doctor. Once these events were undone, the Doctor hoped that Rassilon would retain this development. (COMIC: Supremacy of the Cybermen)

Other references
The "Rivers of Rassilon" was a swear. (PROSE: Twice Upon a Time)

Appearance and clothing
Rassilon's first incarnation had pale eyes. (PROSE: Remembrance of the Daleks) According to one account, Rassilon's first incarnation was a woman with dark skin; (COMIC: Monstrous Beauty) according to other accounts, their first incarnation was a male with brown hair (PROSE: The Legacy of Gallifrey) and bushy eyebrows. (COMIC: Star Death)

Their second incarnation was younger and fair-haired. (PROSE: The Legacy of Gallifrey)

Rassilon was later an older man with a bushy beard when the Eye of Harmony was activated and Gallifreyan Year 0 was established. (COMIC: The Final Chapter, Wormwood)

At the time of the Eternal War against the Great Vampires, a later incarnation was young and beardless. This incarnation regenerated into an older one that was strong and athletic and had a full beard. (PROSE: The Multi-Faceted War, The Scrolls of Rassilon)

During the testing of a Type 1 TARDIS, Rassilon was clean-shaven with a lined face and short, swept-back, grey hair. (COMIC: The Lost Dimension)

During a war against the Nestene Consciousness with TARDISes being used, they had another bearded, male incarnation. This incarnation once again regenerated into a younger body with no beard; he was handsome and jocular. (PROSE: Pandoric's Box)

Their thirteenth incarnation had a bushy moustache that connected to mutton-chop sideburns as well as long, arched eyebrows. (PROSE: Pandoric's Box) Unable to regenerate a thirteenth time, this incarnation was uploaded to the Matrix. (PROSE: Pandoric's Box, The Legacy of Gallifrey)

While in the Matrix, Rassilon took on different appearances. As a member on the council of the Higher Evolutionaries, they had the appearance of his old incarnation with a bushy beard when meeting the Fifth (COMIC: The Tides of Time, The Stockbridge Horror) and Eighth Doctors. (COMIC: The Final Chapter)

When manifesting in his tomb, they had the face of their final incarnation with mutton-chops. (TV: The Five Doctors)

While in the Matrix, Rassilon tried to manipulate the Eighth Doctor into destroying the Divergence. The Doctor refused and cast him into the Divergent Universe. This version of Rassilon had indeed somehow regained a physical presence outside the Matrix, and possessed the appearance of a dark-skinned man with a broad face. (AUDIO: Neverland, Zagreus, The Next Life)

After being resurrected in the body of his descendant Valerian near the beginning of the Last Great Time War, Rassilon had the appearance of a thin old man with short, white hair. (AUDIO: Desperate Measures, Havoc)

Later regenerating after being assassinated by Romana, Rassilon resembled a much younger man with sharp blue eyes and short brown hair and beard. (AUDIO: Deception, Homecoming)

Near the end of the Last Great Time War, Rassilon was in a green eyed incarnation with a grey crewcut. (PROSE: Pandoric's Box, TV: The End of Time)

After being attacked by, he regenerated into the body of an old, nearly-bald man with brown eyes. (PROSE: Pandoric's Box, TV: Hell Bent)

Death
People with major involvement in the DWU and in Doctor Who Magazine, when asked in TEDW 7, were divided over whether the Rassilon seen in the television story The Five Doctors is actually alive or an artificial intelligence or if he had ever died prior to The Five Doctors.
 * According to DWM editor Tom Spilsbury, it hadn't occurred to him before that he was anything other than being alive, and that "it might come down to semantics over what being alive means."
 * Doctor Who scriptwriter Gareth Roberts believed that Rassilon is dead and the face that appears is "a clever AI."
 * Head writer and executive producer Russell T Davies believed that Rassilon is "clearly alive", with his big face in the story being "A projection from the Matrix. A mental life extending beyond the body's death."
 * Novelist, audio writer and comic writer George Mann believed that Rassilon was dead, but the Time Lords had figured out a way of "resurrecting dead people in extreme circumstances," doing "something horrible and timey wimey".
 * Novelist, audio writer, comic writer and DWM columnist Jacqueline Rayner described his condition as "a permanent sleep which is pretty much indistinguishable from death", and that "He's immortal, but he has no awareness," and when the trap inside the Tomb of Rassilon is triggered, "he becomes semi-aware so he can oversee or judge what's going on, before going back into his eternal sleep again".
 * DWM deputy editor Peter Ware believed that Rassilon is dead by the time of The Five Doctors, and his dead mind is speaking from the Matrix to the Doctors and Borusa. He mentions the line from the television story Hell Bent — "Rassilon the resurrected," as further proof that he had died.
 * Doctor Who scriptwriter Mark Gatiss quipped that Rassilon is "biding his time until he regenerates into [actor] ."
 * Head writer and executive producer Steven Moffat, who also wrote Hell Bent, understood that Rassilon was "alive, but in 'eternal sleep'," having got up from his eternal sleep to participate in the Time War, "And got killed. And resurrected. Because that happened a lot in the Time War."
 * According to scriptwriter Terrance Dicks, who wrote The Five Doctors, Rassilon has "gone to a higher plane where he's a benevolent being who can, if he feels it's a big enough crisis, intervene".

Other matters

 * Rassilon was first mentioned in The Deadly Assassin. Prior to this, evidence pointed to Omega (who had appeared in The Three Doctors) as the founder of Time Lord society. A Doctor Who Weekly comic story, Star Death, attempted to reconcile this by having Rassilon and Omega working together. A few subsequent televised Doctor Who stories, such as Remembrance of the Daleks and Silver Nemesis, also took this approach. Remembrances novelisation by Ben Aaronovitch, dipping into the "Cartmel Masterplan", explained that Omega, Rassilon, and another historical figure worked together in enabling the Gallifreyans to have time travel. In the novel The Infinity Doctors universe, Omega states that the Time Lords had not three but six important central figures. These include Rassilon, Omega, the Other, Apeiron, and two others whose names went unmentioned in that source. The novel The Ancestor Cell also describes Apeiron as a founder of Time Lord society, confirming Pandak as another founder and mentioning, in addition, the name Eutenoyar.
 * In Interference - Book One, Sam Jones experiences a "transmission" from the Remote which depicts key moments in the Eternal War. Some details of the transmission are historically inaccurate, in part due to propaganda from Faction Paradox. Other details are filtered through Sam's cultural perceptions; for example, she sees Rassilon as being played by Brian Blessed.
 * Rassilon led a campaign to eliminate the Great Vampires, fighting on the front lines of the conflict for several hundred years. (REF: The Book of Lists)
 * DWM 299 contained a "Gallifreyan panorama" illustrated by Robin Smith. It featured images of Pythia, Richard Mathews' Rassilon, and Omega in the foreground with Bowships, Great Vampires, and a domed city in the background.
 * The statues of Rassilon seen in Supremacy of the Cybermen, especially the Don Warrington outfit, seem to be based off a work of fan art.
 * In the scene corresponding to the point in The Timeless Children where Tecteun's male incarnation stands alongside two other Time Lords in full high-collared regalia, the Timeless Children script release mentions that "we can assume [the other two] are Rassilon and Omega". A promotional photograph of the three actors in costume, released in late 2020 by the official Doctor Who facebook page, shows the Time Lord standing to the left of Tecteun in that shot to be depicted in the exact same costume used for Rassilon in TV: Hell Bent, although this is hard to make out in the televised visuals. The performer playing this incarnation of Rassilon has not been credited or identified, but the 2nd assistant director Mark Corden (who played Omega in the scene) has said that he cast the extra as Rassilon based on his resemblance to Don Warrington.