Aneth

Aneth is a planet with a monarchy. Hymetusite can be found on the planet. They used to be subjects of the Skonnan empire, but they were freed when the empire collapsed. Several generations later, the Skonnans came back, demanding sacrifices of people and hymetusite. (DW: The Horns of Nimon)

The Doctor said he had visited Aneth at some undisclosed point in time and considered it a pleasant place. (DW: The Horns of Nimon)