- "One of the Republic's greatest peacekeepers, Jedi Master Luminara Unduli, is alive. She is being imprisoned unlawfully somewhere in the Stygeon system."
- ―Gall Trayvis, in a hacked HoloNet News transmission
The Stygeon system was a star system located in the Nuiri sector of the galaxy's Outer Rim Territories. The system held at least one habitable planet, Stygeon Prime, which was orbited by at least two moons. During the Clone Wars, the Confederacy of Independent Systems operated a prison known as the Spire on Stygeon Prime. The prison was later operated by the Galactic Empire.
- Darth Maul—Son of Dathomir, Part One (First appearance)
- Droids in Distress book
- Star Wars Rebels – "Rise of the Old Masters" (First identified as Stygeon system)
- The Inquisitor's Trap