Rastaban 2 once had a thriving ecosystem before the gravity of a rogue planet drew it out beyond the habitable zone.
Icebox worlds are places that were once warm enough to support life, but froze over after life started there, leaving a whole biosphere of frozen life-forms. A number of these are found throughout the galaxy.
This can happen for a number of reasons. Some of these worlds were nudged from their habitable orbits by outside influences, another star passing close to their solar system, or the gravity of a rogue planet. Others were warm when their stars were younger, but time has depleted the energy of their suns (often a red giant shrinking into a dwarf star). Icebox worlds can also be caused by volcanism filling the atmosphere with opaque debris and smoke that causes a cooling feedback loop, and in rare cases a civilization arises that creates a nuclear winter scenario.
The first Icebox world to be discovered was Uranus's moon Oberon, which was found to have simple life forms frozen into its icy outer layer.
In some cases, when a planet is still in the habitable zone, terraforming equipment such as heat-mills and atmospheric conditioners is brought in, and the planet is colonized.
The home planets of the Gorox and the Wuxria are considered to be borderline Icebox, but not fully included in this category due to the persistence of advanced lifeforms.
