Coppelius, also called Ghulion IV, was the fourth planet in the Ghulion system. It was a class M planet that was smaller, but denser, than Earth. The planet was orbited by two red moons.
While Soji Asha was undergoing the Zhal Makh, she had a vision that this planet had electrical storms as part of its weather patterns, though the natural environment was quite sunny, with a hot desert-like environment. (PIC: "The Impossible Box", "Et in Arcadia Ego, Part 1")
After the Federation banned synthetic life in 2385, Doctor Bruce Maddox came to this world with Altan Soong and made their base at Coppelius Station, where they created a new generation of organic synths. This facility showed up in the dreams of the android Soji Asha. The Romulans concluded that it was her home. (PIC: "The Impossible Box", "Nepenthe", "Broken Pieces")
General Oh led a squadron of Red Lady-type; warbirds to destroy the planet's population of synths, but encountered orchids and a fleet of Starfleet starships led by the USS Zheng He with Riker in command. (PIC: "Et in Arcadia Ego, Part 1", "Et in Arcadia Ego, Part 2")
Coppelius became a Federation protectorate in 2399. (PIC: "Et in Arcadia Ego, Part 2")