The Rani

Ushas, better known as the Rani and known more formally as Ushas of Miasimia Goria, or, in other accounts, as simply Rani, was a renegade Time Lady and member of the Deca. A brilliant but cold neurochemist, she knew the Doctor and the Master when all three were young, and became an enemy of the former and an unwilling ally of the latter.

The Rani's incarnations
The Rani was, regardless of incarnation, a brilliant scientific genius whose villainy came not from the usual variety of lust for power and suchlike, but from a mindset that treated everything (including morality) as secondary to her research. She was highly intelligent but extremely arrogant, narcissistic, ruthless, powerful and intensely cruel.

The First Rani was a cruel woman whose evil deeds and notoriety had made her the second most wanted criminal in the galaxy, after the Master. (AUDIO: Requiem for the Rocket Men) Much like the Doctor, she had a considerable presence. This presence, however, rested not in a fondness for the planet but as a focal point for her research projects. (TV: The Mark of the Rani, Time and the Rani)

Just as amoral as her previous incarnation, the Second Rani always believed that the end always justified the means. Not above making jokes at the expense of others, she held a great disdain and disinterest in the Doctor's antics. Unlike her previous incarnation, she had a certain level of anxiety in breaking the Laws of Time. (AUDIO: The Rani Elite)

Undated events
In the War in Heaven, the Lord President reintegrated several barely-reformed renegades into Gallifreyan society. One former renegade Time Lady, who was known for her engineered creatures, became a tutor to newly-loomed soldiers. Holsred remembered a lecture in which she connected an artron energy generator to a white rat's brain and then let the rat use the energy to kill a hungry Gallifreyan cat. (PROSE: The Taking of Planet 5)

Father Kreiner had the heads of the Rani and the Master as trophies; however, at least one of them was a clone created in the High Council's hatchling projects. (PROSE: Interference)

Behind the scenes

 * In August 2012, Steven Moffat stated that "he had no reason to bring back the Rani", thus putting an end to the rumours of her return to the television series.
 * Russell T Davies has said that if he had brought back the Rani, he would have cast actress in the role.
 * In the commentary for Last of the Time Lords, Russell T Davies jokingly termed the hand seen removing the Master's ring from the ashes of his funeral pyre "the hand of the Rani". He would later write it being the hand of a disciple of Harold Saxon's in The End of Time.
 * In a email reprinted to Benjamin Cook reprinted in Doctor Who: The Writer's Tale - The Final Chapter, Russell T Davies, choosing to deliberately leave the identity of the Woman ambiguous, anticipates that fans will believe her to be, amongst other possibilities, "even the Rani", "but of course it's meant to be the Doctor's mother."