"At the time of the twelfth,all things will be decided."
- – Close, but not quite.
The Gothic War, otherwise known as the 12th Black Crusade, was a conflict that engulfed the Gothic Sector at the start of the 41st Millennium, as the forces of Abaddon the Despoiler took advantage of a massive warp storm that effectively isolated the sector from the rest of the Imperium.
Prelude to War
The Doom of Arx
Barely a hundred years into the 41st Millennium, the Imperial Navy frigate Ascendance received a garbled astropathic request for aid from Arx,as the world was apparently under attack by unknown forces. When Imperial forces finally arrived on the world four months later, they found the Imperial Guard garrison there wiped out, and the bodies of its soldiers horribly mutilated.
In response, the Inquisition sent Inquisitor Thadus Valconet Horst to the planet, to see if he could find evidence of who perpetrated the massacre. Unfortunately there wasn't a lot left to find, as the attackers cleaned up their tracks unusually thoroughly.
Barely a year after the slaughter at Arx, naval patrols in the neighboring Athena Sector made worrying discoveries, of Imperial warships and merchant vessels drifting through the void, their crew all dead of disease and contagion. Rumors soon spread that these were caused by an ancient Nurgle-aligned warship called the Plagueclaw, and with the increase in sightings of Chaos warships, Horst was worried that a new Black Crusade was in the making. The worlds around the Cadian Gate were put on high alert, and across Segmentum Obscurus Imperial fleets were roused to readiness.
Three years after the attack on Arx, a massive Warp Storm engulfed the Gothic Sector. Isolated from the greater Imperium and cut off from any sort of reinforcement, the brave men and women of the Gothic Sector were on their own.
The Despoiler Strikes
It was at this point that Abaddon makes his opening move, and launches multiple and simultaneuos strikes on naval bases across the sector, in many cases catching Imperial warships unprepared while they were still at dock. Chaos didn't totally have its way however; at Orar Imperial forces struck back, and drove off the invaders, while Ork pirates hounded Chaos fleets once these drifted close to the greenskins' hidden asteroid bases.
The holdings of the Adeptus Mechanicus were also attacked, particularly the Forge Worlds where the powerful Blackstone Fortresses were at anchor. It soon became apparent that these were the Despoiler's primary target, after a fleet of twenty warships overran the defenses of Rebo system just to get at the fortress there.
The worse was yet to come. At the Cardnial World of Savaven, Abaddon revealed his trump card: a warship simply called the Planet Killer. The name was soon proven to be well-merited, as its powerful guns soon blew the planet to pieces, taking with it the lives of 14 billion Imperial citizens.
Inquisitor Horst, still continuing his investigation in the area, soon realized that this powerful warship was powered by two artifacts, stolen in the Gothic Sector years prior: the Hand of Darkness and the Eye of Night.
As if things were already bad enough as it was, but the overall commander of the Imperial Navy of the sector Lord Admiral von Ravensburg, also had to deal with an increase of Eldar corsairs raids taking advantage of the chaos, nevermind Ork and regular human pirates. Forced on the defensive, the Imperial losses continued to rise, without any relief in sight.
Under the Despoiler's Boot Heel
As the Planet Killer had proved itself to be a legitimate threat, it's no surprise that sub-sector after sub-sector surrendered rather than face its wrath.
Abaddon captured his second Blackstone Fortress at Lukaris, and as he deployed these to capture the one defending Fularis II, he revealed what two Fortresses linking their energies could do. Fularis was scoured clean of life by the blast of the linked Fortresses, and soon the Despoiler now had a third Fortress to his name.
Everywhere in the sector the Imperial forces struggled to stem the Chaos tide. Sub-Sector Lysades fell to Chaos control, while at the Cyclops Cluster Ork pirates raided Chaos shipping, allowing the Imperial navy some respite. At Barbarus Costa, Fleet Admiral Mourndark finally broke the back of the Eldar and Human pirate threat in its attack on the Pirates' Haven. Which the pirates dealt with, the Imperial Navy could focus its entire attention on the Chaos invasion again.
At the Hive World of Corilia fifty Chaos Terminators under Chaos Lord Vastakel Khyre teleported directly into the capital spire. There they slaughtered their way through the Planetary Defense Force, before leaving as soon as they came. In their wake, the Imperial Governor and his closest advisors were found missing. What happened to them remains one of the conflict's biggest mysteries.
Raise the Flag of Defiance
The Imperium Strikes Back
Though the Chaos fleet outnumbered the ships of Battlefleet Gothic by sheer numbers, they were also spread out in smaller task forces across the sector. Seeing this as a weakness that could be exploited, Admiral Ravensburg decided to isolate each of these smaller fleets, hit each with the full might of all his available ships.
This plan was soon put to the test when a traitor flotilla was spotted on the way to the Gethsemane System. With seventeen ships of the line and twenty escorts, Battlefleet Gothic tore through the Chaos fleet. The Chaos commander soon ordered his forces to retreat, only to be hit from behind by an Eldar fleet that came seemingly from nowhere. Pincered by these two forces, the Chaos ships were annihilated, giving the Imperium its first major victory of the war.
Things were finally looking up for the Imperium too, as the warp storms that were isolating the Gothic Sector abated, which now allowed reinforcements from neighboring sectors to arrive. With victory suddenly put into doubt, Abaddon led his fleet to the Tarantis System. Once more he combined the might of the Blackstone Fortresses, but this time their wrath was directed at Tarantis' sun. The sun went supernova, and billions died as its heat washed over the worlds there.
The Imperial Navy and its Eldar allies were convinced that another attack was to follow. Thanks to the efforts of Eldar scouts, they deduced that Abaddon was going to make a grab for the Blackstone fortress in anchorage above Schindlegeist, and so decided to set up a trap for the Despoiler there, thanks to access to the Eldar Webway.
Abaddon fell for it hook, line, and sinker, and for the first time in the war found his forces outnumbered and outmaneuvered. For three days the Imperials and Eldar hammered Abaddon's fleet, and in seemingly desperation the Despoiler deployed his Blackstone Fortresses against Schindlegeist's star, seeking to repeat what had occured at Tarantis. In an act of supreme sacrifice, Captain Abridal led his battleship to where the energy of the three fortresses converged. Though his ship was destroyed, the flow of energy was disrupted, which meant it would take time for them to fire again.
Abaddon had enough. With two Fortresses in tow, the Despoiler beat a retreat back to the Eye of Terror. One Blackstone Fortress was left behind, but as marines from the Angels of Redemption soon found it was empty. This Fortress eventually self-destructed, along with all the other Blackstone Fortresses in the sector, leaving the cause of this a mystery to this day.
Even with the Despoiler gone, peace didn't return to the sector immediately. The Imperial Navy and Eldar hounded the Chaos forces trying to escape back into the Eye of Terror. This took two whole years, but with the Chaos threat finally ended, the Imperium could once more focus its attention on freeing the worlds lost to opportunistic raiders and pirates.
The Gothic War lasted almost twenty years, and its legacy could still be felt more than nine hundred years later, when Abaddon's attention once more fell upon the holdings of the Emperor...