Western barrier

The western barrier, also known as the hyperspace tangle, or the tangle, was a chain of hyperspace anomalies that bisected the galaxy west of the Deep Core and prevented exploration of the Unknown Regions for millennia. It formed the midline of the circumferential hyperspace barrier that enveloped the galaxy in a shell of hyperspace turbulence. Though the barrier was believed to have once spanned the length of the galaxy, it had frayed and decayed over millennia in its gradual retreat back towards the galactic core.

Like the circumferential hyperspace barrier, the western barrier was believed by the Pre-Republic specialists, including Dr. Insmot Bowen of the Obroan Institute for Archaeology, to be constructed by the Celestials. Speculation holds that the Celestials had crafted the hyperspace anomalies that bisected the galaxy during the Rakatan revolt in order to contain the Rakata, with the help of their servants, the Gree, the Kwa, and the Killiks. Others believed that the barrier was of natural origins thanks to the "hyperspatial gravitic ripples" or that it have been created by the Celestials as a defensive measure against Mnggal-Mnggal and its infectious intentions, separating Celestial projects in the eastern disk near Corellia, Kessel and other sites.

Despite its reputation as the hyperspace equivalent of a jagged-edged reef, the anomaly line was demonstrably permeable—for instance, Corellian traders had been in contact with the Chiss for many years before their "re-discovery", the planet Ilum was reachable by Force-sensitive navigators, the Rakata homeworld of Lehon was also reached by a Republic naval task force at the climax of the Jedi Civil War and subsequently made a protected historical site by the Republic. Additionally, frontier spaceport worlds in the known galaxy, like Terminus, were known to be visited frequently by transports and traders from the Unknown Regions.

The hyperspace travel to other galaxies was long thought impossible due to circumferential hyperspace barrier. In 27 BBY, Jedi Master Jorus C'baoth believed that the Jedi could use the Force to smooth this zone of turbulence and allow the vessel to pass. He demonstrated this technique on the briarpatch border of the Unknown Regions, and then recommended that eighteen Jedi, including himself, be included in the Outbound Flight Project.

In 1 BBY, a debriefing on Coruscant, held by Dr. Insmot Bowen of the Obroan Institute for Archaeology and attended by General Arhul Kurumenga of the Imperial Department of Military Research, Admiral Conan Antonio Motti of the Imperial Navy, and Master of Imperial Projects Bevel Lemelisk discussed the possible origins of the western barrier.

Daniel Wallace, one of the authors of The Unknown Regions sourcebook, hinted that the hyperspace boundary was created by the Celestials in order to protect themselves from the Mnggal-Mnggal.