The Omens

"The Omens" is the tenth episode in the eighth season of Doctor Who, set on the dead planet of Rauchor. It is seen as the third and final episode in a story arc featuring the White Guardian.

Synopsis
It is the Ch’tar, not us noble K’authon that bring the Internal Dark to form!" - Ganden, leader of the K’authon

After averting a historical disruption in 1192, the White Guardian appears once more in the TARDIS, and instructs the Doctor and his companions to journey to the dead planet of Rauchor where they will find answers, and leaves the Doctor with a message: “He is being reborn. The crafter of Gallifrey”. When they arrive on Rauchor the Doctor becomes increasingly erratic, as the time travellers must deal with two warring factions. Can the doctor learn the truth on the bitter planet, or will he be doomed to linger there without the TARDIS?

Rauchor
As the Doctor calls it, Rauchor is referred to as the worst of worlds. The two factions, the Ch’tar and the K’authon are locked a brutal war for control of Rauchor’s scarce resources, and the Doctor must make peace on Rauchor if he wants to learn more from the White Guardian.