Skonnos

Skonnos was a brown, dirty planet with a grey sky, this may have been caused by the Skonnans or Nimons. The planet was ruled by the first Skonnan Empire, but it collapsed due to infighting. Eventually, they were discovered by the Nimon, who bribed them with advanced technology. Though the Nimons planned to use the energy of Skonnos themselves, they were stopped by the Fourth Doctor, Romana II and K9 (with some help by the Anethan). (DW: The Horns of Nimon)