Rassilon

Rassilon, the First Earl of Prdyon (source?) was the founder of Time Lord civilisation and its perhaps the single greatest figure in Time Lord their history. He was generally considered the first Time Lord, though some believed that distinction belonged to his compatriot Omega. Most of Time Lord society hailed him as a hero. However some contended that Rassilon was in fact a corrupted megalomaniac who tried to murder his friend Omega, and stole his invention to build Time Lord society. During the Last Great Time War, he returned to lead the Time Lords, ultimately, into defat.

Early achievements
Prior to the creation of the Time Lords, Rassilon headed the Prydonian Chapter. With Omega, he planned to make the star Qqaba go supernova. The energy released would enable the Gallifreyan race to travel through time, to become Time Lords. A saboteur from the future known as Fenris, hired by the alien Order of the Black Sun, interfered and caused the "death" of Omega. (DWM: Star Death) (In actuality, Omega survived. DW: The Three Doctors.) but the temporal technology of time controller on Fenris' belt would prove useful to him. (DWM: Star Death)

Rassilon ended the Dark Time and put an end to the matriarchal society of the Pythia. In retaliation, the wrathful Pythia cursed her enemies and made Gallifreyans sterile. (NA: Cat's Cradle: Time's Crucible)

Rassilon brought the Eye of Harmony, in reality the singularity of a black hole, to Gallifrey where it rested underneath the Panopticon (DW: The Deadly Assassin). He invented TARDISes, (REF: The Gallifrey Chronicles) He is implied to have created the transduction barrier that protected Gallifrey (DW: The Invasion of Time), the Looms that birthed new Time Lords and Ladies artificially (NA: Cat's Cradle: Time's Crucible) and the De-mat Gun.

Time Lord history stated the traditions of Time Lord society originated with Rassilon, including the principles of non-intervention (which may or may not be the same as the policy of non-interference) after he had a nightmarish vision of a dictatorial, imperialistic Gallifrey. (DWM: The Final Chapter)

The Time Lords themselves may have been created by Rassilon: the genetic link that enabled Time Lords to travel through time without ill effects was known as the Rassilon Imprimatur, and it is implied that many physiological traits of Time Lords, including the ability to regenerate, were his creations. (BFA: Zagreus)

Rassilon created a living weapon known as the Pariah which he used for missions throughout time and space. Rassilon gave the Pariah independent thought. As a result, the Pariah developed a mind of its own and rebelled against him. Rassilon had no choice but to banish the Pariah from Gallifrey. Rassilon then created Shayde, a more evolved of the Pariah which was incapable of independent thought. The Pariah would go on to to cause the creation of the Threshold. (DWM: Wormwood)

Using temporal technology, Rassilon studied the future. He learned of the Divergence, a race that would eclipse his own within ten thousand millennia. Fearing this potential 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 that all intelligent life evolved in the form of the Gallifreyans, who trapped the Divergence in their own timeline, which Rassilon sealed into a time loop.

He despised the existence of the Vampires and began a purge to wipe them out of existence. (BFA: Zagreus) This took the form of the war against the Great Vampires. Following the war, he 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. (DW: State of Decay)

Artefacts
A great many important Gallifreyan artifacts bore his name. These includes Sash of Rassilon, the Rod of Rassilon (DW: The Deadly Assassin), the Coronet of Rassilon (DW: The Five Doctors), the Harp of Rassilon (DW: The Five Doctors), the Ring of Rassilon (source?), the Great Key of Rassilon (DW: The Invasion of Time), the Black Scrolls of Rassilon (DW: The Five Doctors), the Crown of Rassilon (DW: 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 (first seen in DW: The Deadly Assassin, named in DW: The Five Doctors)

Supposed death
Many rumours also surround Rassilon's death (or lack thereof). One stated that the Time Lords had revolted against him and imprisoned him in the Dark Tower in the Death Zone. Borusa, Lord President and the Doctor's former mentor, believed that Rassilon had discovered a form of true immortality beyond the regenerations known to Time Lords. Borusa uncovered and used several artifacts from the Dark Times, including the Coronet of Rassilon (a mind control device) and the Game of Rassilon. The Doctor discovered the truth when Borusa used him to try and discover Rassilon's secret; Rassilon had indeed discovered immortality, but realised it was too dangerous a secret to share. Borusa was condemned to immortality as a living statue, imprisoned immobile in Rassilon's tomb. (DW: The Five Doctors)

Before he died, Rassilon copied his mind into his creation, the Matrix. (BFA: Neverland) Within the Matrix he sat with other beings. Together they called themselves the High Evolutionaries and had some involvement in the affairs of the universe, using the construct known as Shayde to complete missions for them. (DWM: The Tides of Time) Rassilon and the other Evolutionaries once hired the Threshold to stop a Dalek plan to invade other realities. (DWM: Fire and Brimstone) They later sent Shayde to help the Doctor destroy the Threshold base at Wormwood. (DWM: The Final Chapter)

Banishment
Still in the Matrix, Rassilon began to manipulate the Doctor into destroying the Divergence. Rassilon managed to possess the body of Leela in order to obtain the Ring of Rassilon. The Doctor refused to be Rassilon's puppet and cast him out into the Divergent Universe to end his actions. (BFA: Neverland, Zagreus)

In the Divergent universe, Rassilon planned to steal the Doctor's TARDIS and escape. The Doctor stopped Rassilon and left him behind, while the Doctor and his companions returned to the main universe. (BFA: The Next Life)

Return
During the Last Great Time War, Rassilon was again the Lord President of the Time Lords after replacing President Romana. Now incredibly ruthless and determined to avoid death, he intended to spare Gallifrey from destruction on the last day of the Last Great Time War by using the Ultimate Sanction to turn the Time Lords into beings of pure consciousness, but at the cost of the rest of creation. His plan was defeated by the Doctor, who destroyed Gallifrey by using the Moment. Before the Doctor destroyed Gallifrey, however, Rassilon attempted to break Gallifrey out of the time-lock that blocked the Last Great Time War from temporal manipulation, but was defeated by the Tenth Doctor and was badly hurt by a last attack from a vengeful Master. Rassilon, the Time Lords, and Gallifrey, were all sent directly back to the Time War. The Master's whereabouts are unknown. (DW: The End of Time)

Personality
At first Rassilon was a man who hated corruption and was good at detecting it. He was intimidating and unforgiving but was considered a hero by many Time Lords and Ladies. Indeed he may have even created the Time Lords in the first place and therefore could be a considered a deity among the Time Lords. (BFA: Zagreus) Rassilon was shown to be a charismatic leader who was capable of inspiring his people. However he was also a hypocrite, becoming corrupted by power and his fear of death despite his hatred of corruption. (DW: The End of Time)

After the death of Omega, Rassilon wept for him. The Other mused that Rassilon's actions were born out of love; albeit short-sighted love. (NA: Lungbarrow)

Rassilon was ruthless, power hungry and also appeared to be a madman due to his willingness to destroy the whole of creation. He dreamed of becoming a being of consciousness rather than a physical being. Rassilon was also frightened of death and was even willing to destroy the whole universe in order to survive. (DW: The End of Time) Rassilon had discovered how to become immortal without having to use regenerations to survive. However he believed that the secret was too dangerous to share. (DW: The Five Doctors)

Rassilon was also manipulative, using the Master as a link between Gallifrey and the rest of the Universe which allowed him to temporarily free Gallifrey from the Time Lock. (DW: The End of Time) He also attempted to manipulate the Doctor into destroying the Divergence. (BFA: Neverland, Zagreus) Just before his return to the Time War, he taunted the Doctor, saying that the final act of his life would be murder, after a failed attempt at trying to manipulate the Doctor into an alliance with him, and into killing the Master. (DW: The End of Time)

Behind the scenes

 * Rassilon was first mentioned in DW: The Deadly Assassin. Prior to this, evidence pointed to Omega (who had appeared in DW: The Three Doctors) as the founder of Time Lord society. A Doctor Who Weekly comics 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. Remembrance's novelisation by Ben Aaronovitch, dipping into the "Cartmel Masterplan" explained that Omega, Rassilon and a third historical figure, the Other worked together in enabling the Gallifreyans to have time travel. The Infinity Doctors by Lance Parkin, which features Omega, states that the Time Lords had not three but six important central figures. The names of three remain unknown.
 * Though his Doctor Who Monthly appearances had shown him as a rather foreboding character, and The End of Time painted him as a villain, the much earlier The Five Doctors stated that Rassilon might have had a sinister agenda. Possibly, once he knew the secret of immortality, he grew power-hungry and became something of a hypocrite when it came to his "Watch, and Not Interfere" policy, corrupting the High Council of Time Lords.