The Katurians were a race of advanced humanoids.
Katurians considered 20th-century Earth to be a primitive planet. By this time, they have already mastered space travel and clockwork technology for building sentient robots. Katurian spaceships used ion cells.
The Katurians ruled an empire with dominion over multiple planets. During the reign of Shade Vassily, the empire was overthrown by revolutionaries, who considered Vassily to be a genocidal mass murderer. In their last act before they were overthrown, the Imperial Court exiled Vassily to a primitive planet, Earth, for punishment. They provided technology and an agent, Aske, to ensure a dual goal of keeping Vassily on Earth and keeping him alive.
In 1924, in London, the Ninth Doctor and Rose Tyler became involved in the attempts of Melissa Heart, another Katurian, to revenge the deaths caused by Vassily. After some mistakes, Vassily was eventually killed before he escaped from Earth. (PROSE: The Clockwise Man)