Gatholein

""What happened to the star?" "Nothing. it never had a star.""

- Kara Velian and Celvan, in the Gatholenian orbit

 was a high-gravity, dark, and physically mysterious planet in the Unknown Regions. It was a rogue planet, meaning it had no star to illuminate its surface. However, the geothermal activity kept the surface and atmosphere warm enough for life to develop, though all life was jet black.