Ribos

Ribos was a Grade 3 planet in the constellation of Scytha. It was home to the Ribosians, a civilization with a medieval level of development, and owned by the Magellanic Mining Conglomerate. A large predator known as the Shrivenzale was also native to this planet.

Astronomy
Ribos was located within the greater Cyrrhenic Empire, less then 3 light-centuries from the Magellanic cloud, and it was protected by them. As a Class 3 society, they knew nothing about the outside world and there was no regular commercial space travel to Ribos. Magellanic Mining could not mine until Ribos reached a Grade 2 planet status, which would take many thousands of years. (DW: The Ribos Operation)

Ribos has an elliptical orbit around its sun and so has two seasons of extreme climates: Icetime and Suntime, each lasting approximately 32 Levithian years. The Ribosians believed that the two seasons were caused by the Ice Gods and the Sun Gods, who they thought were fighting over Ribos. (DW: The Ribos Operation)

Landscape
The principal Ribosian city was Shur, though there are backwater settlements to the North. This city holds many important relics, such as the Ribosian crown jewels. Near the centres of the city is the Concourse, the pedestrian area. Underneath all this is the Catacombs, where the dead are stored and a colony of Shrivenzales live. (DW: The Ribos Operation)

History
A Conglomerate-initiated geological survey of the planet revealed the presence of cadmium, bismuth, and iron. Fifty years later, they were about to sell the planet to Graff Vynda-K, an exiled tyrant who wanted to use the planet to build a new forward base, and to turn the population into an army. However, Garron and Unstoffe, conglomerate agents, attempted to sell the entire planet to him by leading him to believe that there was a 0.0001% find of Jethrik, the most valuble substance in the galaxy, on the planet.

The planet was also visited by the Doctor, K-9 Mark II, and Romana I while in search of the Key to Time. (DW: The Ribos Operation)