1. Katerina (Adrienne Hill born 22 July 1937 Plymouth, Devon; died 6 October 1997 ) An inhabitant of ancient Troy, she was a companion of the First Doctor, and was the first companion in the series to die. Katarina appeared in the programme from November to December 1965, appearing in just five episodes.
Katarina is introduced in the serial The Myth Makers, which takes place during the the Siege of Troy. She is a handmaiden of the prophetess Cassandra, and helps the TARDIS crew survive the events of the siege. When Steven is wounded, she helps him into the TARDIS as Vicki decides to stay behind in Troy with the warrior Troilus.
A sweet, simple young woman who cannot really cope with the concept that the universe has suddenly opened up to her, Katarina believes that she is dead, and that the Doctor is a god transporting her to the next life. She refers to the TARDIS as a "temple", and literally worships the Doctor, referring to him as "Lord" (much to his annoyance) and having absolute faith in him.
During The Daleks Master Plan, Katarina is taken hostage by the escaped prisoner Kirksen, who demands that the Doctor take him to Kembel, a planet taken over by the Daleks. To prevent the Doctor giving in to Kirksen's demands, she chooses to trigger the controls to the airlock she is being held in, propelling both herself and her captor into the vaccum of space.
Despite her brief tenure on the series, Katarina is significant for being the first of the Doctor's companions to die on-screen. However, she would not be the last. In some of the tie-in fiction, her death is portrayed as weighing heavily on the Doctor's mind.
2. Sara Kingdom (Jean Lyndsey Torren Marsh (born 1 July 1934) A security officer for Mavic Chen from the 41st century, she would later join the First Doctor and Steven to work against Chen's interests. She appeared in parts four to twelve of the twelve-part 1965 serial, The Daleks Master Plan.
There is dispute as to whether Sara Kingdom was a companion of the Doctor. If we go by recent history, Grace Holloway is classed as a companion to the Eighth Doctor even though she was with him for little over 24 hours. I would therefore, say that she was a companion
Sara is a Space Security Agent, the sister of Bret Vyon, another agent who is aiding the Doctor in trying to defeat the Daleks. Told that Vyon is a traitor by Mavic Chen, the Guardian of the Solar System (who was in league with the Daleks) and ordered to kill whoever is working with him, she shoots her brother and is about to do the same to the Doctor and Steven when they are transported across space to the planet Mira. There she learns, to her horror and grief, that her unquestioning obedience has not only led her to unjustly kill her brother, but also that by doing so she has prevented Vyon from warning Earth of the Dalek plot. She then joins the Doctor in his fight, briefly travelling in the TARDIS to several different locations in space and time as the Doctor and Steven try to return the ship to Kembel for a final confrontation with Mavic Chen and the Daleks.
When the Doctor activates the Time Destructor — a device that accelerates time — as part of his plan to stop the Daleks, he orders his companions back to the TARDIS for their protection. However, Sara follows him, not knowing the nature of his plan but concerned it might fail. As a result, she is caught in the field of the Time Destructor as it rapidly ages everything around it. While the Doctor, being a Time Lord, can withstand the effects, Sara, being human, cannot. As Steven and the Doctor watch helplessly, Sara ages (and is portrayed as an old woman by May Warden) and dies, her remains aging to dust.
Sara is by turns aggressive, independent and ruthless in her pursuit of what was right, a single-mindedness that blinded her to the larger implications of her orders. Meeting the Doctor changes that, and she turns her formidable skill and intellect to the defeat of the Daleks.
When first encountered by the Doctor in England, Earth, 1215 A.D.The King's Demons, Kamelion is a tool of the Master, who is forcing Kamelion to pose as King John. At the conclusion of the Master's previous encounter with the Doctor, he was trapped on the planet Xeriphas. When the Master returns, he has Kamelion with him, calling it a souvenir he had picked up from there. Although Kamelion is sentient to a degree, it is also extremely weak-willed, and therefore open to manipulation by any strong personalities around it. The Doctor frees Kamelion from the Master's grip, and it joins the Doctor in the TARDIS (much to Tegan's disapproval). Here it presumably spends all the intervening time between its two full appearances, out of sight and mind – notably no reference is even made to the character on-screen otherwise.
Kamelion eventually falls under the Master's influence again in the serial Planet of Fire. Kamelion finally begs the Doctor to destroy it, and the Doctor reluctantly honors that request. The Kamelion robot's last appearance is as one of the images of his companions that comes to the Fifth Doctor during his regeneration scene at the end of The Caves of Androzani.
Adric first appears in the Fourth Doctor serial, Full Circle. Attempting to escape from the mysterious Mistfall threatening his community, he stumbles across and finds refuge in the TARDIS, which has been drawn into E-Space via a wormhole-like phenomenon known as a Charged Vacuum Emboitment. He stowed away when the Doctor, Romana and K-9 MkII left Alzarius and becomes a companion in the following serial, State of Decay, accompanying them on the rest of their adventures in E-Space. He remains with the Doctor when Romana and K-9 Mark II leave and the TARDIS finds its way back into its own universe.
With a brilliant mathematical mind and sporting a star-shaped badge (blue enamel with gold backing) for mathematical excellence, Adric is also very well aware of his own intelligence. This, coupled with his relative immaturity, leads to a personality that is abrasive and occasionally crosses over into arrogance. As a result, Adric is one of the least popular companions among fans of the programme. However, it is obvious that Adric also desperately seeks validation from the Doctor as well as those around him, and is often hurt and resentful if he feels he is being sidelined or unable to contribute. As an Alzarian, Adric is a member of a species of extremely adaptable creatures, theoretically capable of genetically evolving to suit any environment, though it is unknown if his particular substrain is capable of this. It is known that he possesses an inhumanly rapid rate of healing, though not to the extent he can regenerate amputated body parts.
Adric is present when, during the events of Logopolis, the Fourth Doctor falls from the Pharos Project radio telescope and regenerates into his fifth incarnation. He continues to travel in the TARDIS along with new companions Nyssa and Tegan, but his travels come to an end in Earthshock when he tries to stop a Cyberman-controlled freighter from crashing into prehistoric Earth. The navigational controls had been locked by logic codes, and Adric is entering the solution to the last code when the computer is destroyed by a dying Cyberman. He dies in the crash, while his fellow crewmates watch in horror on the TARDIS viewscreen. His last words before the explosion kills him are "Now I'll never know if I was right." Adric also dies not knowing that the freighter he was trying to stop was actually destined to be the "meteorr" that would wipe out the dinosaurs.