Ribos

Ribos was a Grade 3 planet in the constellation of Scytha. It was home to the Ribosians, a civilisation 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 and protected by the greater Cyrrhenic Empire, less than 3 light-centuries (300 light-years) from the Magellanic Clouds. According to Bartholomew's Planetary Gazetteer, Ribos was a Class 3 society which knew nothing about the universe beyond their own world, nor did they know they were protected by the Cyrrhenic Empire. As there was no regular commercial space travel to Ribos, Magellanic Mining could not mine until Ribos reached a Grade 2 planet status, potentially taking many thousands of years.

Ribos had an elliptical orbit around its sun, giving it two seasons of extreme climates: Icetime and Suntime. Each lasted approximately 32 Levithian years. The Ribosians believed that the two seasons were caused by the Ice Gods and the Sun Gods fighting over Ribos. (TV: The Ribos Operation)

Landscape
The principal Ribosian city was Shur, which was situated by the tundra, though there were backwater settlements to the North. This city held many important relics, such as the Ribosian crown jewels. Near the centre of the city was the Concourse, a pedestrian area. Underneath this was the Catacombs, where the dead were stored and a colony of Shrivenzales lived. (TV: The Ribos Operation) Some part of the planet created wine. (PROSE: Question Mark Pyjamas)

History
A geological survey of the planet, supposedly commissioned by the Magellanic Mining Conglomerate fifty years beforehand, revealed to the Graff Vynda-K the presence of cadmium, bismuth, iron, and a 0.0001% find of jethrik, the most valuble substance in the galaxy. Con-man Garron posed as an agent for the Conglomerate. Along with his partner Unstoffe, he attempted to sell the planet to the Graff, an exiled tyrant who wanted to use the planet to build a new forward base and raise an army so he could regain his power after fighting in several wars. The faked presence of the Jethrik was intended to add an extra incentive for the Graff to buy quickly.

The planet was also visited at that time by the Fourth Doctor, K9 Mark II, and Romana I while in search of the Key to Time. (TV: The Ribos Operation)