The Bastion-class Commerce Vessel is a large Demiurg vessel equivalent to an Imperial Cruiser in size and status. The Demiurg are a mercantile humanoid xenos species closely allied with the Tau. It is often seen alone or fighting with Tau Navy forces, although even some Imperial Commanders and Imperial Renegades have been known to make use of the Demiurg's willingness to provide mercenary-like services to other races besides their allies in the Tau Empire.
More common than the larger Stronghold-class starship also deployed by the Demiurg, Bastion-class starships are nonetheless only occasionally sighted in the great vastness of the wilderness space along the Eastern Fringe of the galaxy. Bastion-class vessels appear to be more heavily configured for asteroid mining than the stately Stronghold, which is known to function as a factory/processor ship for the Demiurg mercantile clans. Presumably resources and finished manufactured goods are exchanged between these vessels but there are no eyewitness reports of such available to the Imperium of Man. Scattered reports by Rogue Traders operating on the eastern rim of the galaxy indicate that a Bastion-class vessel is crewed by a Demiurg sociopolitical unit known as a "Brotherhood" and that Stronghold-class starships serve as homes to typically 2 or 3 Brotherhoods. It is possible that Strongholds and Bastions form some type of extended affiliation but if this is the case each group must be widely scattered in different star systems many light years apart. The Imperium as yet knows next to nothing about the Demiurg's culture or societal organisation. The one exception to this is when the Demiurg muster for war, which is when two or three Bastion-class vessels gather to protect each Stronghold.
As warships, the Bastion-class compares in firepower and size to an Imperial Cruiser in most respects, though impressive Lance-turrets and battery firepower at close range makes them a thorny prospect for any starship captain to engage. As with the larger Stronghold-class, the Bastion possesses the capacity to launch mining craft and prospector probes reconfigured as Attack Craft and spatial torpedoes.
This class of starship also uses an electromagentic Bussard Scoop to collect stellar hydrogen which it projects through the core of the ship for propulsion, much like its Stronghold-class counterpart. This system also provides the source of fusion power for the laser-based cutting beam the vessel uses to open up asteroids for mining or for puncturing enemy ships' hulls as the circumstances dictate.
- Tau Online Fleet List