Caeruleo 4.1 is a planet-sized moon in the Caeruleo system, 2.14 light-years from Nivenia that orbits Caeruleo 4. Caeruleo 4.1 has no life on its surface, but the Nivenian Empire, specifically the Megastructural Construction Corporation, has commercial interests in using the planet as a secondary base of operations, after Caeruleo 1.
Caeruleo 4.1 is part of the Caeruleo 4 binary planet system. The two planets are close enough to potentially have a space elevator going between them, with a space station/rotating habitat complex in the middle.