Katarina

Katarina was a companion for a very short time. She may also have been the first companion to die while travelling with the Doctor. Before meeting him, Katarina was barely more than a slave. A Trojan, she was the handmaiden of Cassandra, Princess of Troy.

Character Description
Cassandra sends Katarina to spy on the travellers, and in particular Vicki - known by Cassandra as Cressida. Katarina is sent to gather evidence that Cressida is a greek spy. She befriends Vicki/Cressida, who sends her to help the Doctor get the wounded Steven Taylor back to the TARDIS. Once there, Katarina tends to Steven's wounds, and joins Steven and the Doctor on their travels.

Katarina comes from a simpler time. She is from an era which believes in prophecies, auguries, heroic myths, and Gods. She never understands where she is, or what is happening to her. Katarina believes that the Doctor is a God, who is taking her on a journey beyond, in his temple. Despite the Doctor's protestations to the contrary, she remains set in this belief. She firmly believes that this is a devine journey to the 'place of perfection'.

Always loyal to her new 'master', Katarina uses the knowledge she has gained in her short time with the travellers to open the airlock doof on Mavic Chen's spaceship, 'Spar', to sacrifice herself and save her friends. She is certain that her death has been foretold, and that she is doomed to die. Her travels seem to fit into the prophecy. Her self-sacrifice is not, however, because she believes that's the way she's supposed to die. Katarina goes ahead to prevent Kirksen from blackmailing the Doctor into returning the ship to Kembel, and the Daleks.

Quotes
"Can we have reached the Place of Perfection so soon?"

Doctor: "She wanted to save our lives, and perhaps the lives of all other beings of the solar system. I hope she found perfection."

The Daleks' Master Plan