Dathomir was a planet located in the Outer Rim. It was the homeworld of the famous force-witches, who rode rancors across the world's forests and plains. Despite its inherently boring and featureless nature, Dathomir was the subject of much fighting and rivalry in the galaxy.
The Clone Wars revealed that not only did the Nightsisters live on Dathomir, but there was also a tribe of Nightbrothers on the other side of the planet. See, apparently, one side of the planet was for the woman-witches, and the other side was for the man-witches.