Leela

Leela was a warrior of the savage Sevateem, a tribe of regressed Humans. After traveling with the Doctor, she decided to stay on the planet Gallifrey.

Meeting with the Doctor
Leela, the daughter of Sole and friend to Tomas, was one of the Sevateem (the name originated as a corruption of "survey team") descended from the Mordee expedition. As weapons, Leela favored a knife and janis thorns, which caused first paralysis and then death.

Leela profaned the Sevateem's god, Xoanon. Her father died undertaking the ritual test of the Horda on her behalf, and failed. Leela faced the punishment of exile when she encountered the Doctor who resembled the Sevateem's mythic figure, the Evil One. The Doctor had earlier visited Leela's world, repairing the Mordee expedition's computer, Xoanon, and forgetting to remove his own personality from its mind. The conflict between Xoanon and the Doctor's personality had driven Xoanon mad, causing him to split into two personalities, leading it to conduct a long-term eugenics experiment that would eventually culminate in the formation of two disparate groups: the Sevateem, and their enemies the Tesh. The Doctor restored Xoanon's sanity. As he prepared to leave the planet, Leela intercepted the the Doctor and asked to travel with him. He refused, but Leela darted into the TARDIS to the Doctor's dismay, and they set off together after Leela accidentally triggered the TARDIS' dematerialization. (DW: The Face of Evil)

Travels
Although Leela was a primitive, she was also highly intelligent; grasping advanced concepts easily and translating them into terms she could cope with. Despite the Doctor's attempts at "civilizing" and educating her, however, Leela was strong-willed enough to keep her savage ways. She usually dressed in animal skins and went around armed with her knife and Janis thorns, with which she did not hesitate to use on people who threatened her, much to the Doctor's disapproval. Alongside the Doctor, Leela fought Taren Capel (DW: The Robots of Death) and, in Victorian London, Magnus Greel. The Doctor had attempted to show Leela how her ancestors had lived. (DW: The Talons of Weng-Chiang) The Doctor and Leela picked up K9 who had formerly belonged to Professor Marius. Leela killed a number of the Titan Base relief crew who were infected. (DW: The Invisible Enemy) At one point, Leela and the Doctor visited the home of one of the Doctor's former companions, Joshua Douglas, and his family. During this visit, Leela met the imprisoned emperor of the Z'nai, whom the Doctor had contained long ago in the hope of finding an antidote for the plague which Douglas had once released to destroy his people. Douglas' daughter freed the emperor, sparking a new resurgence of the Z'nai empire. For some reason which has not yet been revealed, Leela became the catalyst for the deadly virus, giving her the power to infect the Z'nai with it. This was made easy by the fact that the Z'nai kept their chests uncovered by armor so they would be ever more vigilant against attack. Leela wiped out the Z'nai, all except for the emperor, whom the Doctor imprisoned once again. (CC: The Catalyst)

Life on Gallifrey
Leela trusted the Doctor enough that, when the Doctor, appearing to have gone power-mad, returned to Gallifrey and applied successfully for the position of Lord President of the High Council of Time Lords, Leela still trusted him. Banished from the Capitol, Leela joined the Outsiders, a band of outcast Gallifreyans lead by Nesbin and helped to repel an invading force of Sontarans. Leela had in the mean time fallen in love with Andred of the Chancellory Guard, and decided to stay on Gallifrey accompanied by K9. The Doctor had a second K9 to take along with him. (DW: The Invasion of Time)

She would spend the next few decades of her life in the Capitol. Andred and Leela conceived a child together, the first one born on Gallifrey for millennia. (Pythia had long ago made the Gallifreyans a sterile race.) (NA: Lungbarrow) In later years, Andred vanished and Leela met, and served as bodyguard and confidante to, Lady President Romana - another former companion of the Doctor. (BFG: Weapon of Choice) Leela would get drawn into Time Lord power plays and conspiracies while working on Presidential missions with Celestial Intervention Agency operatives Torvald and Coordinator Narvin. (BFG: Square One, A Blind Eye) Leela discovered that Torvald had caused Andred's death, but it was later revealed that Torvald was in fact a regenerated Andred. (BFG: A Blind Eye) Leela never fully forgave Andred for his deception before his death shortly afterwards. During the troubled time that followed, Leela's most trusted friend, K9, was destroyed in a bomb explosion aimed at the Off-world students of the Time Lord Academy. Devestated and bitter at the loss of her last link with The Doctor, Leela refused to have a replacement unit built. (BFG: Imperiatrix) In the subsequent Time Lord civil war, Leela fought on the side of Romana and was semi-permanently blinded by a prematurely exploding bomb. (BFG: Fractures)

By unknown means, with her sight at last restored, Leela survived the destruction of Gallifrey in the Last Great Time War, though she ended up a prisoner of the Z'Nai, who had somehow managed to return to power. It was revealed at this time that the Time Lords had somehow allowed her to retain her youth for a greatly extended period of time. The Z'nai ended this process, causing her to age one year for each natural day, as they interrogated and tortured her in an attempt to force information about Gallifrey and the Time Lords from her. They had abandoned their ancient custom of leaving their chests vulnerable, now covering their bodies completely in armor. However, just before the Z'nai interrogating her was about to kill her, she gave him a choice - stop the killing or be killed. He merely laughed, and she infected him with the plague that had wiped out the Z'nai originally. It was not long before the entire race was once again destroyed, leaving Leela and the other prisoners at first joyful, then terrified as they realized that they were trapped and abandoned. Leela remained bound, without the strength to free herself, reminiscing about her days with the Doctor as she waited to die. Her ultimate fate is still unknown. (CC: The Catalyst)

Other information

 * When a Rutan ship exploded above Fang Rock, pigmentation dispersal caused Leela's eye colour to permanently change from brown to blue. (DW: Horror of Fang Rock)
 * Leela wrote with her left hand and threw knives and did other actions with her right, suggesting some degree of ambidexterity (DW: The Invisible Enemy).
 * The Doctor commented on the fact that Leela's child would be half-Gallifreyan and half-human. He told Leela to name the child after him. (NA: Lungbarrow) This raises the possibility that Leela's child actually became the Other (although it is not known that the Other was half-human), making Leela, in a way, the Doctor's mother.

Creation of the character
The character of Leela was first conceived by producer Philip Hinchcliffe and script editor Robert Holmes. They wanted a companion in the mould of Eliza Doolittle in George Bernard Shaw's play Pygmalion: a bright but unsophisticated primitive who would learn from the Doctor. Writer Chris Boucher had submitted a story proposal entitled "The Mentor Conspiracy" which featured a character named Leela which fit Hinchcliffe and Holmes's ideas.

Although The Mentor Conspiracy was not produced, Boucher reused the character of Leela for The Day God Went Mad (later renamed The Face of Evil), seeing her as a mixture of Emma Peel from The Avengers and Leila Khaled. Boucher was asked to write two endings to the story, one where Leela left with the Doctor and one where she stayed behind. The decision to have Leela become a companion was made soon after.

Initially, Leela was to have only appeared in three stories. It was later decided that she would stay for all of Season 15. One consequence of this decision was a plot contrivance being added to Horror of Fang Rock to allow the character's eye colour to change, so that actress Louise Jameson would no longer have to wear uncomfortable coloured contact lenses.

By comparison to other companions, Leela ranks as arguably one of the most violent, and is depicted on numerous occasions using deadly force against other humanoids (often to the disgust of the Doctor as in DW: The Invisible Enemy, but occasionally not as in DW: Underworld), or threatening same. Although other companions have been shown killing (such as Romana I shooting a guard in DW: The Pirate Planet), and others have killed in spin-off productions (most notably Jack Harkness in Torchwood), while Ace and others raked up body counts in the novels, Leela remains the only TV companion to be shown killing on a frequent basis.