Aneth

Aneth was a planet with a monarchy. Hymetusite could be found on Aneth. Its people were subjects of the Skonnan empire, but were freed when the empire collapsed. Several generations later, the Skonnans returned, demanding sacrifices of people and hymetusite, both of whom were given as sacrifice to the Nimon. (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)