The Rani is a renegade Time Lady, not a megalomaniac like the Master but a scientist without morals. She conducts experiments with little regard for her "lab mice", focused only on getting her results. At one point, she caused quite a stir on Gallifrey when her giant mice ate the President's cat. The Rani's experiments are often very complex, and she will take personal risks in order to ensure that she has what she needs. Despite this, the Rani is much more careful with her regenerations than either the Doctor or the Master, and she is very cautious and circumspect.
As a result of her chemistry background, the Rani is fond of potions and pills, such as chemically-treated maggots which enslave a person to the Rani's will when they are forced to eat one (yum yum), and capsules of powder that either incapacitate or revive anyone who breathes in the contents. Her control is not maintained solely by chemical means, however; the Rani is equally fond of traps of the more traditional sort. In the past she has used mines that turn people into trees, or spinning bubble traps that explode when the embedded bomb comes into contact with a solid surface.
The Rani makes frequent use of her chunky mini-bracelet, a device that serves as both communicator and control device for the Rani's inventions. She likes to have aliens to control - originally she ruled the planet Miasimia Goria, then later she stopped by Tetrapyriarbus to acquire some Tetrap servants before enslaving the planet Lakertya.
The Rani is also an expert at disguise and imitation. Her talents have enabled her to conceal herself as a haggard old crone and even the Doctor's companion Mel.
