Overview
At the start of the series, the Doctor was identified only as an alien; his home planet and race were not identified. After six years, in The War Games, other aliens from his world appeared and were known as the Time Lords, and it was a further five years before the name of his home planet (Gallifrey) was revealed in The Time Warrior. The nature and history of the Time Lords were gradually revealed as the television series progressed.
The Time Lords are considered one of the oldest and most technologically powerful races in the Doctor Who universe. The small number of beings that are more powerful than the Time Lords include the (now extinct) Osirans and higher powers of the universe such as the Black and White Guardians, and possibly the Eternals. Additionally, The People from the spin-off novels (which are of uncertain canonicity) had a non-aggression treaty with the Time Lords. In the very distant past, the Time Lords fought a genocidal war against the Great Vampires, which led to such a catastrophic loss of life that the Time Lords renounced violence. However, at some point they also entered conflict with the Racnoss, ultimately driving the race to near-extinction save for the Racnoss' Empress and the inhabitants of one vessel hidden deep within what would become the planet Earth ("The Runaway Bride"). In some spinoff media, the Time Lords are also allied with less developed "Temporal Powers." The power of the Time Lords appears limited by their policy of non-interference with the universe and sometimes by intense internecine division. However, the view that they are self-appointed custodians of time developed in the spin-off media, but carried over into the television series; in The War Games the Time Lords return time-displaced humans abducted by the War Lord to their proper time zones on Earth.
In the 2005 television series, Gallifrey has been destroyed and the Time Lords are functionally extinct as a result of a mutually destructive Time War with the Daleks, with only two Time Lords known to have survived: the Doctor and his nemesis, the Master. The Doctor's cloned "daughter" Jenny may also be considered to be a surviving Time Lord, though in "The Doctor's Daughter" the Doctor initially rejected the suggestion. The fate of a fourth member of the race, Time Lady Romanadvoratrelundar (Romana), a former companion of the Doctor, is unknown, as when the character last appeared in the television series she was residing in a parallel dimension. Two other Time Lord-like beings appeared in the episode "Journey's End": Donna Noble, briefly empowered with the mind and knowledge of a Time Lord, and a half-human clone of the Doctor. Donna's memories related to the Doctor, as well as her Time Lord knowledge, were buried in order to save her life, while the clone is currently living out his existence in a parallel universe with Rose Tyler. There is also the question of whether the Doctor's grand-daughter, Susan, was by nature a true Time Lord. She went off to live with a human, David Campbell, in the 22nd century at the end of "The Dalek Invasion Of Earth." Whether she had survived the Time War or if she was not even a part of it is also unknown.
In "Father's Day" the Ninth Doctor remarks that prior to their destruction, the Time Lords would have prevented or repaired paradoxes such as that which attracted the Reapers to 1987 Earth. In "Rise of the Cybermen", the Tenth Doctor mentions that while the Time Lords were around, travel between alternative realities was easier, but with their demise, the paths between worlds were closed, and in "The Satan Pit", he states that his people "practically invented black holes. Well, in fact they did."
The End of Time saw the High Council of Time Lords led by a Time Lord President whom the Doctor named "Rassilon", attempting to escape the Time War by materialising Gallifrey in the place of Earth on Christmas 2009. However, the Doctor destroys the device which allows their passage into the present, sending them back into the events of the Time War.
At the end of "Day of the Moon", a mysterious young girl tells a homeless man that she is dying and then begins to regenerate. The identity of this girl is implied in the episode "A Good Man Goes to War", where it is revealed that the daughter of Amy Pond (Karen Gillan) and Rory Williams (Arthur Darvill), Melody Pond, who later goes by her transliterated name "River Song", has been born with Time Lord-like genetic traits. An old acquaintance of the Doctor's, Vastra (Neve McIntosh) reminds the Doctor that the Time Lord race developed due to their billions of years' exposure to the time vortex. The Doctor then recalls that Rory and Amy had spent their wedding night in the TARDIS; therefore it is theorised that River's conception mirrored that of the Time Lords' genesis and therefore she herself developed Time Lord genetic characteristics.
During the episode "The Doctor's Wife" it was revealed that several Time Lords and their TARDISes had been trapped and destroyed by an entity called House who lived in a separate bubble universe.
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