Keska was a planet visited by the War Doctor during the Last Great Time War. It was home to Rejoice and her father, Thran, and governed by the democratic Keskan Collective.
The Keskans had fled there to escape their previous home, having been forced out by the Taalyens. The aggressors eventually located Keska and tried to invade the planet but they did not succeed because of the artificial force field the War Doctor made using the Keskans' communication satellites. (AUDIO: The Innocent)
Years after the Doctor left Keska, the Taalyens invaded the planet together with the Daleks, and enslaved the Keskans. Keska later became one of the Thousand Worlds in the Null Zone that the Daleks were granted by the Time Lords, setting up a large scale mining operation. (AUDIO: The Thousand Worlds)
When the War Doctor returned to Keska, he found that it, and all the other worlds in the Null Zone, were to be turned into spaceships that would be launched at Gallifrey, destroying it. The Doctor managed to thwart the Daleks' scheme and was later brought by the War Ollistra to Keska's future, where the planet was a thriving peaceful world. (AUDIO: The Heart of the Battle)