The Rani was a renegade time lady, and amoral scientist who considers everything secondary to her research. She was known to enslave entire planets such as Miasimia Goria in order to have a ready supply of experimental subjects and a place to carry out her experiments uninterrupted. Her major interest is in tinkering with other species' biochemistry.
The Rani was exiled from Gallifrey afer some of her lab mice, as a result of an experiment, grew to enormous size and ate the President's pet cat.
Following the Doctor's claims of being the last of his race in the new series, it can be implied that the Rani died at some point before or during the Last Great Time War against the Daleks, although it remains unconfirmed. It is impossible however, that she would have died during the Time War since the Time Lords would never have allowed her to return to Gallifrey for any reason considering everything she had done previously.
- Kate O'Mara earlier appeared as the henchwoman Lisa in the 1969 episode "Stay Tuned" in the TV series "The Avengers".
- Kate O'Mara appeared as the handmaid Alys in the 1970 Hammer Horror film, "Horror of Frankenstein".
- Kate O'Mara appeared later on stage in 1971 as Madame Gerda in the adaptation of the classic British TV series "The Avengers: Stage Play".
- Kate O’Mara appeared as Mrs Elizabeth Peacock in the classic 1990s game show ‘Cluedo’. She is one of four actresses; her times as Peacock was in season two.
- Kate O'Mara appeared as the evil Lady Isabelle in the 1997 episode "Marin to the Rescue" for the action adventure TV series "The New Adventures of Robin Hood".