The Tion Cluster had inhabited Human settlements pre-dating both the Old Republic as well as several planets in the Core Worlds. The Humans were descended from a lost sleeper ship from Coruscant. They developed a mixed society with Rakata castoffs, and utilized some of their technology to create beam tubes circa 27,000 BBY, and eventually limited hyperdrives that relied upon fixed-position hyperspace beacons. Rakata Force-sensitive technology was also present in Xim's war-robots.
The limited technology prevented the Tionese from having contact with the Core, who eventually forgot their origins and remained isolated from the rest of the galaxy. The Tionese, however, soon fell upon Hutt Space, resulting in a disastrous war that shattered the region. The Cluster joined the Galactic Republic in 23,900 BBY.
The cluster is divided the into three sectors: the Allied Tion Sector, the Tion Hegemony, and the Cronese Mandate (the former territory of the Cronese Sweeps). The Cluster was at the edge of one of the galaxy's spiral arms. Just Coreward of the Cluster was the Cron Drift and the former Jedi stronghold of Ossus. The Perlemian Trade Route passed close to the cluster at Lianna.
The Cluster contained about 12,000 stars, orbited by almost 600 habitable planets. Of these 600, 464 were part of the Cronese Mandate. The other 136 were divided between the Tion Hegemony and the Allied Tion.