Celwis's largest satellite, a terrestrial moon, could be found in the Unknown Regions. It orbited Celwis, a planet under the control of the Chiss Xodlak family within the Chiss Ascendancy. This moon featured a cliff hiding the derelict Chiss frigate called Midsummer. The frigate had been abandoned there following the Xodlak family's reduction in status from a ruling family to a member of the forty Great Families. Approximately 18 BBY, the Xodlak family reactivated the Midsummer with the intention to claim a world rich in the metal nyix.
The 2021 novel Thrawn Ascendancy: Greater Good, the second book of The Ascendancy Trilogy by Timothy Zahn, referenced Celwis's largest moon.