thanks to TARDIS Wikia/Wikipedia
Liv Chenka was a female human originally from the planet Kaldor, and a companion, of the Doctor in his seventh and (primarily) eighth incarnations. Before encountering the Doctor, she worked as a spaceship medical technician.
ENCOUNTER WITH THE SEVENTH DOCTOR
Liv served aboard The Lorelei cargo spaceship. She encountered the Seventh Doctor shortly before a group of Voc robots began to attack the crew of her ship. She helped the Doctor to discover that the Voc robots were not behind the attacks, and found that the ship’s security chief, Farel, dressed as a robot when instigating an attack. Liv and the Doctor then prevented Farel from crashing the Lorelei into Ventalis. Liv stayed behind on Ventalis after the Doctor had departed. (Robophobia)
TRAVELS WITH THE EIGHTH DOCTOR
Liv was present on Nixyce VII when the Daleks invaded. She was used by the Dalek time controller to be a source of compassion amongst the natives of Nixyce VII. It was here she encountered the Doctor for the second time, although she did not recognize him at first because he had regenerated since they last met. Eventually she was convinced of his identity, and she helped in with his plans to turn the Daleks against an Eminence fleet nearby. (The Traitor)
Liv eventually fled the Dalek invasion, in the bowels of a cargo ship, but suffered severe radiation poisoning as a result, which compromised her metabolism, and condemned her to death, be it through embolism or renal f ailure, whichever would strike first. (The Reviled)
Because of this, she signed up as a med-tech on the science vessel Orpheus and went into cryo-sleep on board for a thousand years. She awoke when the Orpheus had reached the edge of the universe. Liv once again met the Doctor on board the Orpheus, shortly before it came under attack from the Eminence, and it began to possess the crew. Liv planned on blowing herself up next to a piece of the Eminence in order to stop its plan, but was rescued by the Doctor. She promptly joined him on his adventures. (Time’s Horizon)
Liv travelled with the Doctor to London in the 1970s, where she helped the Doctor to defeat the Master and the Eminence. After they were defeated, the Doctor made Liv stay behind in London with his companion, Molly at his home in Baker Street, due the fact that they had met out of order – he had to play out the events in which Liv first met him on Nixyce VII. (Eyes of the Master)
When Molly O’Sullivan disappeared, Liv suspected the worst and was able to fashion a crude communications device from the technology of the era, and sent out a distress call which was intercepted by Coordinator Narvin, of the Celestial Intervention Agency. (The Death of Hope)
Liv was later sent by Narvin, to help the Doctor fight the Master and the Eminence, sending her to Ramossa, where she worked to improve the conditions of the humans refugees of the Eminence War who had settled there, alongside the native scorpion-like Ramossans, who began to depise their visitors and the danger they placed them in. When the humans were isolated into a ‘quarantine camp’, Liv worked to make conditions livable and acted as a medic to the injured, while waiting for the Doctor to arrive. Once he did, together, they worked out a way to make sure the humans escaped an incoming Eminence attack, however, their plan failed resulting in the complete destruction of the Ramossans, their world, and the Master securing the refugees for his own purposes. (The Reviled)
Scared by the Doctor‘s determination to avert the war, but willing to go along with him, she snuck aboard the private research complex of Professor Markus Schriver, the man responsible for the eventual creation of the Eminence itself, and posed as an assistant sent to him by the Ides Scientific Institute. She became concerned by his mental health, but facilitated a meeting between him and the Doctor, which only reinforced the fact he was slowly loosing his sanity. Her cover was blown by the arrival of Dr. Sally Armstrong, working for the Master, and she would have died during a neural extraction procedure if Shriver’s insanity hadn’t caused him to trap Sally inside a second chamber and program the computer to decide which one would undergo the procedure through random chance. Due to her condition, Liv was ready for death, but in the end survived when the computer ‘chose’ Sally instead. She was then taken by the Master instead to play nursemaid to Molly, who was suffering from the mental conditioning and retro-genitor particles that Master had assaulted her with. (Masterplan)
Liv was present on Earth as the Master set up his final endgame, with the eventual result that all of humanity was slave to his will, only able to keep Molly stable and calm during her moments of wakefulness. When Narvin,, working with the Doctor, tried to rescue her, she tried to shot the Master with a hidden firearm, but his hypnotic abilities caused her to believe she was finally succumbing to her illness. However, the Master revealed it was all in her mind, and that her continuous exposure to the particles inside Molly had in fact cured her of the radiation poisoning. She was eventually rescued from the Master‘s grasp by the Doctor, and sent by him to take control of a nearby television communications hub, which proved essential to ending the Master‘s control over the Earth, and defeating the Eminence in the here and now. Afterwards, she was invited onboard the TARDIS as a full fledged companion,, even being given a TARDIS key of her own, and said her farewells to Molly, who was to be sent home by Narvin, for her own protection. (Rule of the Eminence) She visited London 1921 when the Doctor was looking for Molly.
She hated looking out of place in her usual attire, so wore clothes of the era. the Doctor then asked her to take Martin Donaldson out on the town. When Martin took her to see a Buster Keaton film she pointed out the flaws in it. The Woman was looking for her. (A Life in the Day) She went to Paris with the Doctor when he tracked the TARDIS to there. She talked to Georges Legrand which led her to Adelaine Dutemps. She kicked down the Doctor‘s artist friends apartment door. She told the Dalek Time Controller about the outcome of The Eminence war. (The Monster of Montmartre) Live was disgusted that the Master was working with the Daleks. She got used to being taken prisoner by the Daleks. She expected the Master of being better than using the Daleks. She attacked the Master with the Perfume the Doctor gave her in Paris, and stole his Tissue Compression Eliminator. She went to Moscow with him to find the Doctor. She blew Molly O’Sullivan’s cover there. (Master of the Daleks)
She became worried after Molly became ill after they arrived in the Eye of Orion. The Time Controller then took her to see Markus Schriver’s final experiments. She witness the birth of the Eminence. The Dalek Time Controller wanted her to transfer his mind into the gas the Eminence were composed of, she wouldn’t. She wanted the Dalek Time Controller to die to save billions. She took Molly home after her sacrifice. (Eye of Darkness)