Gothic War (12th Black Crusade)
Over the course of history, the various Blackstone Fortresses were abandoned. Six fortresses were discovered in various star systems of the Gothic Sector of the Segmentum Obscurus, and were claimed by the military forces of the Imperium of Man, modified and integrated into the defense infrastructure of the various star systems.
The Fortresses were dormant, easily boarded and occupied. Although inactive, there was enough residual power in their power grids to allow the humans to live in them and turn them into powerful spaceborne hardpoints that were central to the fortifications in the systems they occupied.
However, during the Gothic War, Abaddon the Despoiler was influenced by the C'tan known as 'The Deceiver' to find a pair of ancient devices, (known as the 'Hand of Darkness' and the 'Eye of Night', probably Eldar devices with some kind of command code or password) which re-activated the massive ships, bringing them under his control. Once awake they were able to shed their grafted-on Imperial equipment and glide slowly through space under their own power, using their original warp-cannon in place of the turrets and fighter bays the Navy had built onto them. There is also a record of a boarding party that made its way into one of the activated fortresses and described it as like a living thing, pulsing with power. As the war progressed and Abaddon acquired three Fortresses, he was able to combine their warp-cannon attacks to obliterate worlds and stars. The Blackstone, like most Eldar technology of that scale was equipped with an infinity circuit of some kind. However when it fell into the hands of Chaos, it was corrupted and possessed directly by the Chaos God and enemy of the Eldar, Slaanesh.
At the end of the Gothic War, the fortresses were attacked by a vast fleet of Imperials and Eldar, and Abaddon retreated into the Eye of Terror with two activated Blackstones, while the remaining Blackstone was re-captured. When the aforementioned boarding party boarded the Blackstone Fortress, the remaining three in Imperial custody simultaneously disintegrated.
13th Black Crusade
During the 13th Black Crusade, Abaddon the Despoiler used the two Blackstone Fortresses he had captured during the Gothic War against the Imperium of Man's defenders. One of these was used to attack the world of Cadia, obliterating Cadians and Chaos troops on the surface indiscriminately. This Blackstone Fortress was attacked by Eldar and Imperial battlefleets, but both took huge losses from the Chaos warfleet guarding the structure. The great Eldar Farseer Eldrad Ulthran boarded the fortress, attempting to remove the taint of Chaos and return the fortress to Eldar control. As the fortress had been possessed by a portion of the mind of the Chaos God Slaanesh, Eldrad's body was destroyed, but his mind remains trapped within the construct. After Eldrad's assault, the fortress stopped attacking Cadia and concentrated on its own defence. It was later attacked by a Necron fleet, which was attempting to destroy the greatest weapon of their ancient enemies, the Old Ones. The Necron fleet failed in this effort and was destroyed, but it caused enough damage to the fortress that it finally retreated from Cadia and back into the Eye of Terror.
There are unconfirmed reports of the other Blackstone Fortress in the hands of the Forces of Chaos being destroyed by similar Necron raiders.
Viewed from the top the shape of an activated Blackstone Fortress has warped to resemble the eight-pointed star of Chaos Undivided (this is somewhat ironic considering the fortresses are of Old Ones' creation).
- Battlefleet Gothic Rulebook
- Codex: Eye of Terror (3rd Edition)
- The Thirteenth Black Crusade (Background Book)