The second planet of the Calline system was a tide-locked, atmosphere-less planet. The half of the planet facing the sun was intensely hot and uninhabitable, while the part facing away from it was as cold as vacuum. Between these two halves was a thin habitable zone. At one time it was very seismically active, and lava caves riddled its crust. The Rebel Alliance investigated it for a base c.2 ABY, but found smugglers using it already as such. Because of their antipathy for the Galactic Empire, the smugglers might have been willing to join forces and turn over the base to the Rebels.
Sources
- Rebellion Era Sourcebook (First mentioned)