Tuven III

Tuven III was a mining planet.

Robots controlled by Quan were misdirected by greedy human miners to exploit the planet until its surface was reduced to a sea of endless, dead, unnaturally-regular sand. Descendants of the minors survived in underground tunnels, worshipping Quan, who had gone into hibernation, as a kind of deity as the Fellowship of Quan. Finding out about Quan, an incarnation of the Master killed and replaced the Sentinel of Quan, the leader of the cult. However, he realised that the Fellowship-members were unable to translate a key inscription, as was the Master himself.

Guessing that the Doctor would be better able to translate it, he used another one of the old machines to create a localised spatial vortex which drew the Sixth Doctor's TARDIS off-course. The Doctor believed Tuven III to have always been an uninhabited dead planet, and was dismayed at the discovery of the tunnels alone. Captured and taken before the "Sentinel", the Doctor and Peri were led to the chamber where Quan was in stasis, where the Master revealed his true identity to the two. However, instead of the docile machine the Master had expected, Quan was a fully independent entity who made its own choices. The Doctor convinced him that the Master was not to be trusted, and Quan promised to instead help the Fellowship make the planet habitable again. With the Master's true identity and motives revealed, the cultists began to crowd around the Master with murderous intent. To Peri's shock, the Doctor refuses to help the Master and simply leads her back to the TARDIS despite the Master's pleas. (PROSE: The Fellowship of Quan)