Battlefleet Corona - 13th Black Crusade: In 999.M41, war came without warning to the Belis Corona Sub-sector, and the opening moves by the Forces of Chaos saw large number of plague-ridden Space Hulks entering Imperial space. Though many were intercepted by the Space Marines and destroyed, some managed to escape the Astartes' attention. Some of these foul vessels of contagion found their way into the Belis Corona Sector, spreading their disease and pestilence amongst the masses throughout the sector. Along with the adjacent Agripinaa Sector, they were some of the first to bear witness to the rise of hordes of infectious, undead zombies that threatened billions of people on many of the Imperial worlds within the sector. This plague was later named the Curse of Unbelief.While the defence of the Cadian Gate from the Forces of Chaos continued to go badly upon the surface of many worlds in the Cadian System, in particular Saint Josmane's Hope and Solar Mariatus, the war in space was fought more on the Imperium's terms. The Cadian System had been the focus of Abaddon's primary fleet actions, and the Imperium's fortunes there changed from day to day. The situation was highly fluid and the Chaotic naval forces found themselves stretched to exploit the victories they had won.A fleet the size of which has not been seen since the end of the Gothic War eight standard centuries earlier had been dispatched from Cypra Mundi, and arrived at Belis Corona in preparation for a massive Imperial counter-offensive into the Cadian Gate. The arrival of this vast armada allowed those Imperial vessels that had been fighting continuously since the beginning of the invasion a brief respite. Severely depleted ship’s companies were bolstered through indiscriminate press-ganging, and hasty repairs and refits were undertaken on those vessels most in need of them.The Imperial reinforcements were split into battlegroups, each tasked with bolstering the defences in a specific sector of the Segmentum Obscurus. The regions around the Eye of Terror encompass many millions of cubic light years, and only by the concentrated application of resources in those areas in most desperate need could the Imperial Navy hope to make inroads and slow, stall, and eventually repel the Chaos warfleets plaguing the region. A small number of Imperial Navy ships won a decisive victory when they managed to hold back a larger Chaos Fleet at the Ilthirium Belt, buying time for Battlefleet Agripinaa to arrive and allow the remaining ships to retreat. This course of action however, left the Agripinaa Sector open to invasion and soon the worlds of this sector and the Belis Corona Sub-sector was transformed into nightmarish realms of plague and pestilence.Upon arriving at the Cadian Gate, the Doom Eagles Space Marine Chapter dispatched forces to a number of warzones, notably areas that had already suffered terribly at the hands of the Forces of Chaos. The largest of these detachments, under the command of Captain Luctus of the 3rd Company, was involved in operations within the Belis Corona Sub-sector, where the notoriously pious Chapter battled those who had fallen to the Curse of Unbelief. Only those without the strength of faith to resist were afflicted by the Zombie Plague, and it has been noted that not a single Doom Eagles Battle-Brother was affected by its blight. The Doom Eagles proved effective in combating the Plague Zombies infesting many worlds of the sub-sector, though, typically for this aloof Chapter, they had refused all offers of support in consolidating these successes.The Cadian Sector High Command was also briefed by the Ordo Xenos on a number of other factions which assailed Mankind as the Forces of Chaos battered at the doors of the Cadian Gate. The Inquisition warned the Cadian High Command to be alert for seemingly incongruous reports of alien infiltrations in the region near the Subiaco Diablo System, particularly for attacks coming up from below the galactic plane. They would not expound further on what they meant by this, but insisted that the Cadian High Command should inform the Inquisition immediately should any such attacks by unknown xenos materialise. Despite being beset on all sides, the Imperial forces and their commanders remained imbued with a sense of righteous indignation. If every damned creature in the galaxy was now ranged against them, then they were determined to take them all into oblivion with the last cry of the human race.The Imperial forces largely held at Belis Corona, the location of the greatest orbital shipyard of the Imperium, which suffered the worst excesses of a Tyranid splinter Hive Fleet, and the horrific plagues bestowed upon its hive cities by the Death Guard Traitor Legion. At the height of the invasion, something truly unexpected occurred. Defenders in the outlying star systems reported contact with Tyranid organisms -- at first individual vanguard-organisms such as Lictors, but soon entire broods of Genestealers and Hormagaunts. A splinter fleet of Hive Fleet Leviathan, a Tyranid fleet known to be attacking up through the galactic plane, was taking advantage of the mass destruction initiated by the Chaotic invasion to gain a foothold in strategically vital Imperial space. Faced with both the pestulant forces of the Death Guard, and the voracious hordes of Tyranids who were, unlike the human defenders, immune to the Plague God's blessings, the forces of the Imperium were hard-pressed to defend the vital worlds of the Belis Corona Sector. It was the intervention of the forces of the Eldar of the Ulthwé Craftworld and then the orbital bombardment of Laurentix that allowed the forces of the Imperium to fight back, despite the disastrous ambush of forward elements of Battlefleet Solar at the Bairsten Prime Warp jump point. Subiaco Diablo saw the Convent of the Order of the Ermine Mantle hold out against overwhelming odds, though at terrible cost, before being relieved by a host of Adepta Sororitas units drawn from across the region, thanks to the leadership of the renowned Canoness Astra.