Lord Rassilon, also known as Rassilon the Redeemer and Rassilon the Resurrected, was an engineer and architect regarded as the greatest single figure in Time Lord history and the founder of their modern civilisation. He served in the capacity of President of the Council during both the early history of the Time Lords and at the time of Gallifrey's destruction during the Last Great Time War.
Although Rassilon's later reputation was that of the founder of Gallifrey's modern civilisation, he was contemporarily regarded mainly as an engineer and architect. (DW: "The Deadly Assassin") He was known to have built the quantum force field around the planet. (DW: "The Invasion of Time")
The people of Gallifrey had learnt the secret of time travel, but to make it a reality they required a colossal source of energy. Using a remote stellar manipulator that would receive the mythical name of the Hand of Omega, a stellar engineer that legends called Omega created the supernova that was the initial power source for Gallifreyan time travel experiments. Omega, who was thought to have been destroyed in the supernova but was actually swept into the resulting black hole, left behind the basis upon which Rassilon founded Time Lord society. (DW: "The Three Doctors", "Remembrance of the Daleks")
The Book of the Old Time gave the account thusly: "And Rassilon journeyed into the black void with a great fleet. Within the void, no light would shine and nothing of that outer nature continued in being, except that which existed within the Sash of Rassilon. Now Rassilon found the Eye of Harmony, which balances all things, that they may neither flux nor wither nor change their state in any measure. And he caused the Eye to be brought to the world of Gallifrey wherein he sealed this beneficence with the Great Key. Then the people rejoiced." (DW: "The Deadly Assassin")
Wearing a sash that protected its wearer from being sucked into a parallel universe, Rassilon stabilised all the elements of the black hole (including the Eye, its nucleus) and set them in an eternally dynamic equation against the mass of the planet. Although all the power of the Time Lords devolved from it, "Rassilon's star" was later thought to no longer exist or to have always been a myth. (DW: "The Deadly Assassin") The fame of his deed was such that there was a galactic legend about his discovery of the Eye of Harmony. Although they did not even know of his planet of origin, the civilisation of Urbanka were aware of his involvement in this event. (DW: "Four to Doomsday")
When Rassilon was still young, a race of giant vampires appeared out of nowhere and swarmed all over the universe. Because the output of energy weapons would only be absorbed by the giant vampires, Rassilon ordered the construction of bowships, vessels that fired bolts of steel that would kill them by destroying their hearts. The Time Lords hunted them down across the universe in a war so long and bloody they were sickened of violence forever. Thousands of the vampires were killed by the Time Lords, but when the bodies were counted it was learned that the King Vampire had vanished from time and space. It was the directive of Rassilon that any Time Lord that came across "this enemy of our people and of all living things, shall use all his efforts to destroy him, even at the cost of his own life." (DW: "State of Decay")
As President of the Council, Rassilon knew that no president without the Great Key could have absolute power. To protect the Time Lords from dictatorship, he gave the Key into the hands of a chancellor. (DW: "The Invasion of Time") In the days before Rassilon, the ancestors of the Time Lords had abused their considerable powers by setting up the Death Zone, a region of their planet walled with an impenetrable force field, and kidnapping other beings with the time scoop to take part in the Games. Rassilon put a stop to the Games by forbidding the use of the time scoop and sealing off the entire zone. (DW: "The Five Doctors")
The official history of his life depicts him favourably, but there were many rumours and legends that stood contrary to the generally accepted version of events. Some of these rumours hold that his fellow Time Lords rebelled against his cruelty and locked him in the Dark Tower in eternal sleep. Although he was said to have been dead for aeons by the time of the Doctor's first presidency - attested to by the fact that his mind could be found in the APC net with other deceased Time Lords - the extent of his powers were not truly known and some thought that he was still alive in his tomb. (DW: "The Five Doctors", "The Invasion of Time")