The Rani is a renegade Time Lord, an evil scientific genius whose villainy comes not from the usual variety of lust for power and suchlike, but from a mindset that treats everything (including morality) as secondary to her research; she has been 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 — she was exiled from Gallifrey after some of her lab mice, as a result of an experiment, grew to enormous size and ate the President's pet cat. A past relationship between the Rani and the Doctor is hinted at, but never elaborated upon. It is established they are the same age.
The Rani was created in an attempt to give the Doctor another recurring foe like the Master, but eventually only appeared in two serials, The Mark of the Rani and Time and the Rani, before Doctor Who went off the air in 1989. The Rani also appeared as the principal villain in Dimensions in Time, the Doctor Who charity special created for Children in Need. She was intended to appear in another serial entitled Yellow Fever and How To Cure It but the show was put on hiatus and the serial was cancelled.
In her initial appearance, the Rani had removed the need for sleep from the alien subjects on Miasimia Goria and the planet had collapsed into chaos, as without sleep the aliens turned violent. To restore order and continue her experiments, she began stealing the chemical that allows sleep from human brains, carrying this out in violent periods of Earth's history so her experiment's after-effects would go unnoticed. When carrying this out during the Luddite rebellion, her operation was co-opted into the Master's attempt at hijacking the Industrial Revolution and killing the Sixth Doctor, and as a result her operation was thwarted.
In this episode, the Rani is ruling the planet Miasimia Goria, and on Earth (disguised as an old lady running a wash house) to extract brain fluid from random miners who come into the wash house after their shift. However, the Master appears. This is Anthony Ainley's first appearance since Planet of Fire (Peter Davison's penultimate serial in 1984), and the Doctor and his companion, Peri (Nicola Bryant) are shocked, as they believed the Master to have been destroyed.
Eventually, the Doctor traps the Rani and the Master in the Rani's TARDIS, where an embryo of a Tyrannosaurus rex starts to grow as the result of a time spillage.Seventh Doctor. When the Doctor (Sylvester McCoy) wakes up, he figures out what the Rani is doing, and a Tetrap (from the planet Tetrapyriarbus) knocks him out when he threatens to smash a piece of machinery. The Rani then injects the Doctor with an amnesia drug, and disguises herself as the Doctor's companion, Mel (Bonnie Langford), and later uses a hologram of Mel to get the Doctor to return a vital piece of machinery.
The Rani manages to escape in her TARDIS, however, the Tetraps are also in there, and have her take them back to Tetrapyriarbus to help them with their larger tasks.
In August 2006, the tabloid newspaper The Sun reported that the Rani would return in the 2007 series, played by Footballers' Wives actress Zöe Lucker. This was subsequently denied by the BBC, and when aired the 2007 series did not include any appearance or mention of the Rani.
Near the end of the 2007 series finale "Last of the Time Lords", a female hand with red nail polish is seen picking up the Master's ring while evil laughter of The Master echoes in the background. In the podcast commentary of the episode, Russell T. Davies jokingly refers to it as "the hand of the Rani", and also states that they will not be picking up on that scene next year — he just put it in there to give any future production teams something to use if they want to bring back the Master. In Doctor Who Magazine, Davies explains that he "didn't know the Rani was that well known" and that the hand was not actually intended to represent the Rani.
In August 2007, The News of the World claimed that former Dynasty actress Joan Collins had signed up to play the Rani in the 2008 series . This report was also corroborated in TV Week. When aired the 2008 series did not include any appearance or mention of the Rani. Also, Kate O'Mara appeared on the Antony Cotton Show stating that she would be interested in reprising her part.
Pip and Jane Baker wrote her as the lead in the BBV audio drama The Rani Reaps the Whirlwind, following on from Time And The Rani, and also wrote her as the villain in a Choose Your Own Adventure-style children's game book entitled Race Against Time.
The Past Doctor Adventure Divided Loyalties, by Gary Russell, states that the Rani was one of a group of promising young Time Lords called "the Deca" which included many future renegades, including the Doctor and the Master. The novel also gives her given name (or at least its first syllables) as Ushas (a reference to the Vedic goddess of that name).
The Rani briefly appears in an artificially created parallel universe in the Past Doctor Adventures novel The Quantum Archangel. In this reality she, the Master, the Meddling Monk, and Drax are posing as a group of German scientists.
In Dimensions in Time, the Rani attempts to capture all the Doctor's incarnations in a time loop. She is seen to be travelling with a companion called Cyrian.
The short story "Rescue", by David Rodan (who also wrote the special) reveals how the Rani rescued Cyrian from a Cyberman invasion of his home planet. It was published in the Doctor Who Yearbook 1995.
As of the serial The Day of the Clown, a character named Rani Chandra has joined the cast of Doctor Who spinoff The Sarah Jane Adventures. However, producer Russell T Davies has told readers of Doctor Who Magazine that Rani is "not the Rani".
Unlike the Doctor's TARDIS, the Rani's TARDIS has a fully functional chameleon circuit, and can still disguise itself wherever it lands.
In Mark of the Rani, the Rani hides her TARDIS (disguised as a cabinet) behind a screen, and has managed to link it to, as the Doctor says, a Stattenheim remote control, which he describes as "genius". It is in this TARDIS that she and the Master get trapped with a gradually growing Tyrannosaurus rex embryo.
In Time and the Rani, her TARDIS appears as a reflective pyramid. She is eventually trapped by the Tetraps in her TARDIS.