Oswin Oswald was a human serving as a Junior Entertainment Manager onboard the starship Alaska when it crashed into The Dalek Asylum.
Biography
Oswald initially tried to escape the Asylum but was found and converted into a Dalek. Unlike other members of the Alaska, who were partially converted by the nanocloud, she was fully converted, due to her exceptionally high intelligence. In Dalek form she created a dream world for her human mind to dwell in to forget the truth. Under this life, she assumed that she was surviving on soufflés and hacked into Dalek systems.
A year later, she aided the Eleventh Doctor, Amy and Rory in finding safe passage, wiping the memory of the Doctor from the Daleks' telepathic web in the process to save him. The Doctor attempted to rescue her, but discovered she was a Dalek and revealed it to her. Oswin first attempted to exterminate the Doctor, then broke down over what she had become.
Oswin lowered the Asylum's defenses so the Parliament of the Daleks could destroy the planet, and Amy, Rory and the Doctor could escape back there, to find out that Oswin had erased the Doctor from the memories, not only of the ones in the Asylum, but of every single Dalek in the Parliament as well. Oswin later presumably died when the Daleks blew up the Asylum. (DW: Asylum of the Daleks)
Personality
Oswin had a flirtatious and feisty personality, cheerfully flirting with the Doctor and Rory Williams. She had deluded herself into thinking that she was human and was devastated when the Doctor revealed that she was actually a Dalek. Oswin had a strong willed nature and unlike most Daleks she was not driven by a mindless hatred of all other forms of life nor did she lose any of the emotions she had possessed as a human. Notably she was the only Dalek that the Eleventh Doctor displayed any compassion or pity for. Oswin was selfless, allowing the Doctor to complete his mission to blow up the planet, even though she was on it and telling him to leave her behind and escape with Amy and Rory. She was also extremely intelligent and it was because of her intelligence that she was turned into a Dalek; she displayed a knowledge of Daleks and their technology that exceeded even the Doctor's partially because she had been transformed into a Dalek herself. (DW: Asylum of the Daleks)