Battlefleet Orpheus - The Dark Marches Crusade: In the sixth century of M.36, following the tumultuous times of the Age of Apostasy, the Segmentum Tempestus knows a strong resurgence which it put to good use when the tremendous Warp Storms that had given the Segmentum it’s name abated. Segmentum authorities launched a series of campaigns and Crusades designed to expunge lingering threats and fortify the Imperium’s southern border. This would eventually lead to the great Dark Marches Crusade, whose principal objective was to reconquer and colonize the domains that had been explored by the legendary Rogue Trader Lady Arica Orpheus in the distant past of the Great Crusade but had been lost in the wake of the Horus Heresy. The Crusade was led by a distant descendant of the noble Rogue Trader house, Lord Tempestus Hal Orpheus and would lead to the creation of several new Imperial Sectors, chief amongst them the Orpheus Sector which was granted its own Battlefleet. The newly constituted Battlefleet was given a mighty vessel as its flagship, the Apocalypse-class Battleship Arica Dominus from which Hal Orpheus had planned and directed the Dark Marches Crusade and chose Amarah Prime, the Sector’s new capital, as its principal base of operation and headquarters.Over the next millennia, Battlefleet Orpheus always upheld its oaths, watching and protecting the Sector’s worlds and the vital commercial routes may of them relied upon even during the dark years of the Times of Woe, when the political structure of the Sector was close to imploding. Most often, the Battlefleet saw limited actions against Eldar Corsairs which had found refuge within the asteroid fields and nebulas of the Hesod Nebula. This domain, located to the far North of the Sector could never truly be controlled or pacified, despite several punitive expeditions being launched. Following the loss of contact with the neighbouring Leyak-Sector in 976.M37, Battlefleet Orpheus is tasked with the surveillance of the border to this Sector which is declared Perdita after an Ordo Xenos-led investigation. Several frontier worlds within the Orpheus Sector are also to be abandoned, and Battlefleet Orpheus establishes a strong presence in the Deluvian Sub-Sector to better enforce the compliance of local space-traffic. This was only made possible through an inquisitorial mandate for the other worlds of the Orpheus Sector to dramatically increase their own orbital defences, which freed sufficient ships for these patrols along the southern border to be carried out. It is believed that it was during these years that Amarah Prime equipped itself with the two great orbital stations that would still make up the heart of its orbital defence network during the Orphean War. It was also presumably following these edicts that Battlefleet Orpheus established a secondary mustering point and astropathic choir in orbit around the Relic World of C'syn'ad.With its eyes fixed on the outside, the Orpheus Sector did not see the dark seeds that had taken root within their Sector as the baleful touch of Chaos corrupted a score of worlds. Still heavily hindered by the tremendous military tithes they were subjected to, the worlds of the Orpheus Sector proved to be fertile ground for the promises of insurrectionists, separatists and demagogues. Sector governorship had long passed from the extinguished line of House Orpheus to the stewardship of the House of Laan, distrusted by many for the House’s reputation was one of intrigue and excesses. To some extent, the Sector was kept together and functioning only by the tireless efforts of Battlefleet Orpheus, which successfully adverted a number of crisis that would have plunged the Sector into chaos had they not done so. Chief amongst these menaces was the major Ork-invasion of 160.M39, where their ramshackle fleet penetrated deeply into the Deluvian Sub-Sector. Led by their gigantic flagship - the Mega-Kroozer - the Orks proved a far more tenacious opponent than initially believed and it took Battlefleet Orpheus no less than nineteen weeks of constant attacks to slow down the WAAAGH!, before defeating it with the help of its allies, the Space Marines of the Revilers and Red Seraphs Chapters. However, the Orkish survivors soon settled in the desolate regions on the border of the Deluvian Sub-Sector and would soon prove to be a constant thorn in the Battlefleet's side. Focusing on the regions surrounding the Warp Storm known as the Shattered Deeps, these Orks soon turned to piracy, preying on the commercial routes of both the Deluvian and Drucillan Sub-Sectors.Battlefleet Orpheus only played a limited role during the Orphean War of Faith, an Imperial Crusade destined to cleanse the Orpheus Sector from the corruption of the xenos and the Ruinous Powers that had befallen it. The Orphean War of Faith was essentially a ground war and although Battlefleet Orpheus contributed largely in shipping Imperial forces to the front lines, few naval battles were fought. This changed to some extent after the events known as Saint Marduk’s Bane, when in 921.M39 an unknown enemy scoured the planet clean of both Chaos-aligned and Imperial armies and destroyed Saint Marduk’s supporting fleet elements. Having mysteriously vanished, Battlefleet Orpheus diligently searched for the enemy, the desire for retribution burning hot i their hearts, but all patrols came back empty-handed.It would only be in the 40th Millennium that Battlefleet Orpheus’ might would be tested again, when the Orks of WAAAGH! Gutgouga succeeded to rally the pirates of the Shattered Deeps around them and push for the Deluvian Sub-Sector. It would take nearly seven month of gruesome campaigning to stop the Ork advance and destroy them, Warboss Badrok Gutgouga’s corpse being famously hanged from the spire of the Red Cathedral on Amraphel. This marked the last true threat to Battlefleet Orpheus before the disastrous Orphean War.