Rassilon was a Gallifreyan Time Lord and one of the founders of Time Lord society at large. Having discovered a reliable form of immortality (TV: The Five Doctors), Rassilon faked his death and holed himself up in the Tomb of Rassilon for millions of years, presiding over the timelines and playing his hand through deceit (PROSE: The Eight Doctors, TV: Do You Have a Licence to Save This Planet?). He returned to the world of the living for the Last Great Time War. (TV: The End of Time, Hell Bent)
Rassilon was a complex figure, wise and intelligent beyond mortals' knowing, but for this very reason arrogant and dismissive of “lesser” beings' needs. Fascinated by the possibility of godhood, he gladly sacrificed even his staunchest allies for a chance at ultimate power, as shown by his arranging the death of Omega and even planning to destroy Time itself to make himself and the rest of the Time Lords into gods. (TV: The End of Time) Though he had been instrumental in implementing it, Rassilon came to see maintaining the rigid web of time as more of a chore than anything else, and commanding lesser men to do his work for him was more of an expedient of laziness than a machiavellian gambit. (TV: Do You Have a Licence to Save This Planet?) Possibly connected to his arrogance was Rassilon's propensity to name all objects built by, or belonging to, him, some variation of “the [X] of Rassilon”.
In the Dark TowerEdit
While entombed in the Tomb of Rassilon, Rassilon, shortly after receiving a shipment of Toasters of Rassilon from the Deliveryman, foresaw the threat of the Licensor and his Licensed Reality Corporation posed to Time Lord dominion, and to the universe at large. He attempted to contact the Second Doctor, but, as he was not in his TARDIS when Rassilon contacted him, grudgingly turned to the Chiropodist instead. Tipped off, the Chiropodist headed to Unlicensed Earth, where he lured and eventually destroyed the Licensor. (TV: Do You Have a Licence to Save This Planet?)