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The '''Orpheus Sector''' was an [[Imperial]] [[Sector]] of [[Segmentum Tempestus]]. Its last [[Sector Lord|Sector Governor ]] was [[Calibron Laan]]. After a devastating [[Necron]] [[Orphean War|invasion]], the [[High Lords of Terra]] declared its dissolution in 999.M41{{Fn|1b}}.

During the [[Horus Heresy]], the savage civil war saw the regions of the sector under control torn apart by lawlessness and anarchy. Neither the forces of the [[Emperor of Mankind|Emperor]] or nor [[Horus]] controlled the region. During the bloodshed of the [[Scouring]], the [[Alpha Legion]] warlord [[Dynat Mal]] fled to the Sector's [[Mandragoran Stars]]. Dynat's forces, known as the [[Shadowed Ones]], employed guerrilla tactics and dark forces to take over much of the region. This sundered realm eventually became known as the '''[[Dark Marches''']].{{Fn|1a}}.

The Orpheus Sector was not formally established under after the [[Age of Apostasy]], when Segmentum authorities launched a series of crusades. The most successful was the [[Dark Marches Crusade]] under Lord Tempestus [[Hal Orpheus]], which brought over six hundred worlds under the rule of the Imperium. The arcing band of space was subdivided into four sectors: '''[[Haxan Sector|Haxan''']], '''[[Leyak Sector|Leyak''']], '''[[Eurydice Sector|Eurydice''']], and '''Orpheus'''. The aging Hal Orpheus, kept alive only through the arts of the [[Adeptus Mechanicus]], became the first sector [[Sector Lord|sector governor]], ruling from [[Amarah Prime]]. Favoured [[Imperial Guard]] regiments received [[Arcantis]], [[Gedrid]], and [[Midwinter]], while the Adeptus Mechanicus received [[Myre ]] in perpetuity{{Fn|1a}}.

In [[976.[[M37]], all contact was lost with Leyak Sector. In response, the Orpheus Sector authorities increased their military tithes, constructed orbital defences, and forbade colonial expeditions into the Veiled Stars on pain of death. These restrictions increased civil tensions in the sector. Authorities brutally suppressed riots, rebellions, and [[cult]] activities across the sector. When the [[Black Crusade of Von Mallas|Black Crusade of Von Mallas the Transgressor]] the Transgressor reached the sector in [[113.[[M38]], it caused further uprisings on [[Saint Marduk's Bane|Colkasth]] and [[Epirus]], draining resources required to fight the Transgressor's forces. [[MorrosLachrymal]] Lachrymal was founded as a penitentiary world to hold the rebels, but the fighting had ruined Epirus, which would take decades to recover even a shade of its former productivity{{Fn|1a}}.

A sudden and mysterious attack struck the [[agri-world]] of [[Tlaloc]] in [[889.[[M38]]. A squadron from [[Battlefleet Orpheus ]] found the world annihilated with no intact bodies or recording devices to tell them what enemy had destroyed the world so swiftly. The Lord Commander declared the world under permanent quarantine while [[Inquisitor]] [[Kussan ]] of the [[Ordo Xenos]] believed the [[Dark Eldar]] were responsible for the attack.{{Fn|1a}}.

After nearly a thousand years of strife and warfare, its worlds bleeding resources to fight wars elsewhere and reinforce the sector capital's defences, and infighting amongst sector nobility, the Orpheus Sector erupted in [[Orpheus Revolt|civil war]]. Rebels in the [[Drucillan Cluster ]] overthrew the government and declared their secession from the sector, rallying other rebels to their cause and undermining the sector's stability. The parliament of [[Amraphel ]] hired xenos mercenaries to fight their enemies, only to become the victims of the [[Khrave]] they had hired. Imperial authorities learned that the [[Chaos|Great Enemy]] had orchestrated most of the unrest.{{Fn|1a}}.

In [[903.M39]], hope came to the fractured sector in the form of a crusade fleet. At the head of the fleet stood [[Arch-Confessor]] [[Marduk (Imperial)|Marduk]] of Helvamon. Marduk declared a [[War of Faith]] for the souls of the Orpheus Sector, claiming to have received a warning from the God-Emperor himself of a great and terrible threat to mankind rising from the darkness of the sector. The Arch-Confessor provided a figurehead and a rallying point for the resistance against the dark powers. By 921, the Imperial forces had effectively destroyed the enemy, with only one holdout on Colkasth. The [[Angels Revenant]] strike cruiser ''[[Intercessor (Strike Cruiser)|Intercessor]]'' investigated the sudden cessation of Astropathic communication with the ground forces: two extremely powerful xenos void craft ambushed it on the edge of the system, but ''Intercessor'' destroyed one and drove off the other. The damaged ship can only watch a raging battle in-system via long-range auguries and by the time ''Intercessor'' reaches reached orbit, the attacking force has fled, leaving Colkasth a burning, irradiated wasteland. The Angels Revenant sorted out the few survivors and the planet was renamed Saint Marduk's Bane.{{Fn|1a}}.

In [[819.[[M41]], a contagious madness spread across the [[Industrial World]] of [[Chemarium II]]. The [[Chaos Lord]] and self-styled "Beggar King" [[Ranker Nonesuch]] led his insane followers to destroy Imperial manufactoria and slaughter Imperial forces. Nonesuch then spread his uprising to the rest of the system. [[Inquisitorial Stormtrooper]]s were dispatched to aid the suppression campaign while an exclusion zone was established around the system.{{Fn|1a}}

In [[990.[[M41]], a sudden shockwave through the [[Warp]] extinguished the turbulence that had plagued the western Orpheus Sector for three centuries, causing celestial instability across the region. [[Astropath]]s, [[psykers]], and [[witch]]es across the sector went mad or simply dropped dead. Many void ships were blown off course or destroyed. Panic and mass hysteria gripped the Drucillan Sub-sector. At the same time, the [[Adeptus Mechanicus]] reported that the binary stars of the Caracol system unexpectedly went supernova. The [[Ordo Malleus]] believed that the events were precursors to a major [[daemonic]] incursion into the region. Imperial authorities ignored the Caracol supernovae, deeming the matter insignificant.{{Fn|1a}}

*[[Altun: ]] — [[Dead World]]*[[Caracol: ]] — Dead World*[[Cutlar: ]] — Dead World*[[Nightshard: ]] — anomalous celestial mass*[[Uxmal: ]] — Dead World  In addition to the above, the sector contains 57 minor systems not notable.

==See also=Sub-sectors====Related Articles===*Capitoline Sub-sector*Deluvian Sub-sector*Drucillan Sub-sector*Eleven secondary administrative regions*Seven exempted divisions[[List of sectors]]