The Rani
The Rani (Originally known as Ushas) was a renegade Time Lord. She knew both the Doctor and Master when they were younger.
Biography
Youth and Exile:
Ushas belonged to the same Academy group, the Deca, as the First Doctor. She was the same age as the Doctor. At the Doctor’s graduation, there was an incident involving a giant rat. After Ushas grew mice to enormous size and they at the Lord President’s cat, she was exiled but she hijacked the TARDIS that was delivering her and became a renegade known as the Rani.
Life as a Renegade
Even though she didn’t care for Earth, it was the focus of several of her research projects. At some point, she visited the Earth and acquired several Tyrannosaur embryos.
She enslaved the planet Miasimia Goria and experimented on the people. They became restless and violent as a side effect. The Rani visited Earth at various points in its history to extract chemicals from the human brain which enabled a person to sleep. This caused the humans she took the chemical from to become violent and uncontrollable. Her presence in Earth history brought about various wars.
The Rani traveled to various planets, experimenting on the inhabitants to suit her own ends and her love of Chemistry.
Personality
The Rani was an evil (or more precisely amoral) scientific genius whose villainy came from a mindset that treated everything secondary to her research. She was known to enslave entire worlds in order to have a supply of experimental subjects. Her major interest was in altering the biochemistry of other species.
She may have been evil, but she found the Master to be truly evil and stupid. She said his plans were overcomplicated. She did evil things because she felt it necessary for her work and often showed a conscience.
Appearances
Mark of the Rani (TV)
Time and the Rani (TV)
State of Change (Prose)
Divided Loyalties (Prose)
The Quantum Archangel (Prose)
From Wildthyme with Love (Prose)
Something Borrowed (Prose)
The Rani Reaps the Whirlwind (Audio)
The Rani Elite (Audio)