The Bastion was erected by the Stybla family circa 5000 BBY during the initial days of the Chiss Ascendancy, the nation of the Chiss species. Its purpose was to safeguard an alien superweapon referred to as the Starflash, with the intent of never deploying the weapon. However, centuries down the line, in the midst of a war with an enemy of the Ascendancy, the Chiss were compelled to utilize the Starflash in order to shield their surviving population from the approaching fleet of their foe. Subsequently, the Universal Analysis Group (UAG) took over the Bastion's role on the Ascendancy planet Sposia, becoming the new protector of the alien artifacts amassed by the Chiss.
The 2021 novel Thrawn Ascendancy: Lesser Evil, which is the concluding book in Timothy Zahn's Star Wars: The Ascendancy Trilogy, referenced the Bastion in flashback sequences.