Rassilon is a fictional character in the British science fiction television series Doctor Who. In the backstory of the programme, he was the founder of Time Lord society on the planet Gallifrey. After the original television series ended in 1989, Rassilon's character and history were further developed in books and other media.
Rassilon's contributions to Time Lord culture and society were immense, and his name both reverberates and is honoured throughout Time Lord history. The Rassilon Imprimatur is the name given to the symbiotic nucleus that allows Time Lords to withstand the molecular stresses of time travel and grant them a link to their TARDIS time machines.
Several other Time Lord artifacts named after him have a technological function, in addition to their ceremonial roles:
Rassilon is also given credit, variously, for TARDIS technology; the living metal and superweapon validium; and the transduction barriers that protect Gallifrey. How much of this is true and how much of it is propaganda and good public relations is not certain. In The Two Doctors (1985), the Sixth Doctor claims that Rassilon enjoyed fishing and advocated its practice by Time Lords, but on questioning by Peri, admits he may have just made it up.
The Tomb or Tower of Rassilon, also known as the Dark Tower, stands in the middle of the Death Zone — a blasted, barren plain — on Gallifrey. The Death Zone was used, in a period of Gallifrey's history known as the Dark Time, as an arena that pitted warriors of various alien species and times (captured by the use of a device called the Time Scoop) against each other in gladiatorial games, although the Second Doctor tells the Brigadier that Rassilon put a stop to the games (The Five Doctors, 1983). It was rumored that Rassilon, who lived during this time, had been deposed by Time Lords rebelling against his rule. It was also claimed Rassilon had discovered the secret of immortality and was still alive in the Tower, sleeping. The quest to reach Rassilon's tomb and the secret, blocked by a series of deadly obstacles, is referred to as "The Game of Rassilon".
In The Five Doctors, Time Lord President Borusa wants Rassilon's secret for himself, describing Rassilon's immortality as "perpetual bodily regeneration". Borusa uses the Time Scoop to transport the Doctor in all his regenerations (along with various companions) to the Death Zone, using them to clear the way to the Tower. However, Rassilon's promise to share immortality with whoever overcomes the obstacles in the Tower and solves the Game of Rassilon is actually a trap designed for would-be dictators. Borusa is granted immortality by being transformed into a living statue. In that story, Rassilon (played by Richard Mathews) appears as a disembodied image floating above his own sepulchre, but whether this is a telepathic projection or an interactive recording of some sort is unclear.
If Rassilon continued to exist in some form after his apparent death, the recent destruction of Gallifrey in the Time War renders his current status even more uncertain.
In the last three stories of Alan Moore's run on Doctor Who Monthly we see the first Time War in Time Lord history, where the Order of the Black Sun make a pre-emptive strike on the Gallifreyans' experiments with time travel. In the first story, "Star Death" (Doctor Who Magazine #47), we see Rassilon gaining the equipment to control time travel thanks to the failed initial attack. In the DWM comic strips, Rassilon is shown existing in the Matrix as part of a council of "Higher Evolutionaries" acting as the guardians of Time (The Tides of Time Part 2, DWM #62, among others).
In the Doctor Who audio plays produced by Big Finish Productions, Rassilon is voiced by Don Warrington in Seasons of Fear, Neverland, and Zagreus. In those plays, he was also shown to continue to exist in the Matrix. He is also portrayed, not as a benevolent figure, but a master manipulator willing to preserve Time Lord history and society as he knew it at all costs.
At the end of Zagreus, the Doctor was exiled to the Divergents' universe. He eventually tracked down Rassilon in that universe, and discovered that he had been manipulating an entity called the Kro'Ka to observe and control the Doctor and Charley's actions. At the end of the events of The Next Life, the Doctor and his companions escaped the timeless Divergent universe, but Rassilon and the Kro'Ka remained trapped.
In the spin-off novels, the partnership of Rassilon and Omega in Time Lord history is rounded off by the shadowy figure of the Other. The continuity of other media in relation to the TV episodes are to date, uncertain.