O'reen was a fortified planet in the Unknown Regions.
Originally founded as one of several long-range Republic military colonies following the Great Hyperspace War, it was meant to be an early warning outpost for attacks from outside Republic space. Such a system was conceived to prevent sudden invasions, learning from the recent attacks by Naga Sadow's Sith Empire. O'reen was eventually forgotten by the Republic as the program was cancelled and four of the five long-range colonies were disbanded.
O'reenian civilization continued in isolation, fortifying its cities and raiding passing spacecraft, partly in order to get information about the goings-on in the civilized galactic society as well as to keep the colony's location a secret. O'reenian society grew to become thoroughly militarized and paranoid about outside influences. At its peak, the world was as heavily fortified as any of the Fortress worlds in the Core region of Palpatine's Galactic Empire.
The world was lead by a commander given the honorific of "Magnus", after the surname of the starship captain who forcibly took control of the then-abandoned colony and made it into a viable fortress. Despite several attempts by civilians to force changes in O'reenian society, the world remained a military colony with brutal suppression of dissent.
Despite its civilian technology not being as advanced as the rest of civilized space, O'reenian society poured resources into its military force to make it comparable, tech-wise, to the Republic and the Empire that followed it.
- The Unknown Regions (First mentioned)