Battlefleet Corona - Segmentum Obscurus: The Segmentum Obscurus, also known as the Segmentum Obscura, is the region of Imperial space to the galactic north of Terra. This Segmentum of the Imperium of Man is the home of the vast Warp Storm and Warp Rift called the Eye of Terror, the primary home for the Forces of Chaos in the Milky Way Galaxy. The Imperial Navy's Segmentum fleet headquarters is located on Cypra Mundi, which also serves as the central headquarters of the Imperial military's Segmentum Command. The Segmentum Obscurus is the area of the Imperium most often under deadly threat by attacks from the Eye of Terror and is also the site for all of Abaddon the Despoiler's Black Crusades. As such, it currently is home to the majority of the Imperium's armed forces, which were most recently mobilised to a state of readiness not seen since the Horus Heresy as a result of the 13th Black Crusade in 999.M41.The constant turmoil surrounding the Cadian Gate requires the fleets of Battlefleet Obscurus to be far more active than many other Segmentum battlefleets. The whole sector exists in an almost perpetual state of readiness, and as such the demands on manpower and resources are huge. Vast numbers of new, inexperienced ratings frequently have to be drawn up to replace those lost in the constant fighting. However, those that survive the harsh first years of military service around the Cadian Gate rapidly mature to become some of the most capable leaders in the Imperium. As with all highly militarised zones, it is important for the Imperial Navy to maintain substantial reserves of vessels around the Eye of Terror, ready to deploy as reinforcements should the need arise. Whilst it is possible to keep the vessels themselves ready in this manner, Battlefleet Obscura simply does not possess the manpower to keep reserve crews stationed aboard these vessels as well. Instead, whole orbital shipyards are filled with rows of silent, inactive vessels, often representing classes of warship now outdated or scarce.In times of great need, these ships will be brought into service and crewed with ratings from destroyed or crippled vessels or even with hastily mustered new recruits, meaning the crew is unlikely to have any familiarity with their new vessel. A posting to such a reserve fleet is thus considered an unnerving duty, forcing a rating to enter deep into an unfamiliar vessel which may have lain dormant for centuries. Much superstition surrounds such fleets and perhaps because of this, unusual behaviour of both crew and vessel is rather commonplace. Reserve fleets are used only reluctantly by the Imperial Navy, and only in the most desperate of circumstances, but an invasion the size of Abaddon's 13th Black Crusade without doubt qualifies as exactly that -- the most dire of circumstances, the most desperate of times.In a reserve fleet, all vessels are prone to certain unexpected events, such as mass panic or even mutiny amongst the crew, inexplicable noises, sensor readings and sightings or disconcerting setbacks and failure of machinery. Against Chaos fleets, where the followers of the Dark Gods are able to exert their influence to further unsettle their already nervous opponents, unforeseen events can be even more devastating.