Cellin is a volcanically active moon thronged with geysers that orbits Crusader (Stanton II), and is the planet's closest natural satellite. Its tenuous atmosphere contains trace amounts of oxygen, but not enough to support respiration. In spite of the toxic air, many residences and outposts have been established on Cellin since Phillip Xu constructed the first permanent homestead in 2906. The moon was named after the character Cellin from the popular Human children's story A Gift for Baba.
