The Krasi were a warlike alien race.
Although they were equally as ruthless as other alien races, they wanted to appear benevolent and they went to a lot of trouble to present a good public image.
In a new timeline created by Josiah W. Dogbolter's Quantum Possibility Engine, the Krasi tried to take over the solar system which had become a closed system due to Dogbolter's temporal manipulations. Though they tried to portray themselves as liberators, the Krasi were forced to retreat when the Seventh Doctor had the people of the system record their invasion, calling them out on their actions. (AUDIO: The Quantum Possibility Engine)