Magnus (planet)

Magnus Epsilon was a planet colonised by humans from third Earth. It was ruled by a matriarchy, as most of the males died from a gender-specific virus in the atmosphere that reacted to sunlight.

The virus didn't affect women or aliens like Time Lords. The Ice Warriors tried to make it their new home by changing its orbit to one farther from their sun, making it colder and more habitable for them. They initially succeeded, but the Sixth Doctor managed to return Magnus to its original orbit. (AUDIO: Mission to Magnus)