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 Taalyens 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. They were drilling on the planet's core to destroy Gallifrey. (AUDIO: The Heart of the Battle)