The Bastion Inviolate was an Imperial Fists' Starfort. Alongside the Endeavour of Will, it helped guard the region of Imperial space around the Eye of Terror from the forces of Chaos. The Bastion Inviolate was attacked by the Iron Warriors Warsmith Shon'tu in 998.M41, leading to the Battle for the Endeavour of Will. During the battle, the Bastion Inviolate had its Machine Spirit infected by a Daemon-virus, leading it to become hideously mutated and rendered defenseless. However, the pure Machine Spirit of the Bastion Inviolate managed to regain control towards the end of the battle, grabbing onto the Iron Warriors Grand Cruiser Ferrous Malice and activate its Warp Drive, plunging both ships into the Warp. This was done to save its sister ship, the Endeavour of Will.