The Rani is an exceptionally talented Time Lord whose main talent is neurochemistry; she is also an outstanding genetic engineer. Her completely unethical approach to her experiments, however, resulted in the Time Lords banishing her from Gallifrey, and she is forced to experiment wherever she can temporarily set up a base. Her TARDIS is a monument to her genius: inside, preserved or dormant specimens of creatures are displayed like ornaments in glass containers.

Although the Doctor has ruined her experiments in the past, she considers herself above the need for petty feuding. The Doctor is merely a brilliant tool for her to use to further her experiments, and she seeks him out only when his talents are necessary to success. Her great talent for disguise, however, means that the Doctor often fails to recognize her and only too late realizes who he is up against. The Rani uses stealth and subtlety to achieve her objectives, and seldom tries to be too clever for her own good. Her traps, however, are usually elaborate.

Human beings are a particularly rich source of raw materials for her experiments: the Doctor has said she regards people only as walking heaps of chemicals. She also uses chemicals and drugs rather than mental powers such as hypnotism to ensure obedience. It does not matter to her whether the drugs cause pain or death; such side effects are not enough to make her abandon her experiments.

Out of her disguises, the Rani is a strikingly attractive and imperious woman. Her heart-shaped face has high cheekbones; her eyes are a chilling blue-grey. Long, brunette hair tumbles down over her shoulders and back. She typically wears futuristic clothing: a crimson, sparkly tunic, crimson trousers and red-leather mid-length boots. On her left wrist she wears a broad, metallo-plastic bracelet which provides audiovisual communication with her minions and spy cameras, as well as operating scientific apparatus.