Oseidon was the homeworld of the Kraals, and the only inhabited planet in the Mutter's Spiral with an unstable level of radiation that was increasing all the time.
In the 8th century, (AUDIO: The Oseidon Adventure) the Kraals fought "one atomic war too many," as the Fourth Doctor explained to Sarah Jane Smith, with not many of them surviving and the planet being ruined. He assured her they hadn't been exposed long enough to get radiation sickness, but also stated that it wouldn't be too long before the planet would be uninhabitable for the Kraals, (PROSE: Doctor Who and the Android Invasion) although he later told Leela that the Kraals had endured twelve centuries of exposure, with the predominant form of radiation being O radiation which was harmful to life. He also stated there were other Kraals in subterranean bunkers. (AUDIO: The Oseidon Adventure)
Similar to Earth in terms of gravity and atmosphere, the Kraals planned to invade the planet in the 1970s. In their preparation, a reproduction of the English village of Devesham and the adjoining Space Defence Station was created where the Kraal android's were tested by Styggron (TV: The Android Invasion) and the First Kraal Army, before being defeated by the Fourth Doctor and Sarah Jane. In 1979, Grinmal lead the Second Kraal Army, assisted by the Master, in a second invasion attempt of Earth, creating a second reproduction of Devesham. However, the Fourth Doctor and Leela thwarted the attempt. (AUDIO: The Oseidon Adventure)
Oseidon Robotics were one of the companies present at the Fluren Temporal Bazaar on Fluren's World. (COMIC: Weapons of Past Destruction)