The Night Reapers were a former Loyalist Space Marine Chapter that fell to the corruption of the Ruinous Powers and were eventually declared Excommunicate Traitoris, becoming a Renegade Chapter of Chaos Space Marines. The Night Reapers Chapter was eventually hunted down by the combined Imperial forces of the Grey Knights, Red Templars and Minotaurs Space Marines aboard the ancient pre-human Space Hulk designated the Perun Cross.
The Night Reapers' path to corruption began when they were condemned to Crusade on the fringes of the Laanah Rifts region following their actions during the abortive Defence of Salvation-Gamma in the midst of the Constantinus Iconoclasm. Their crime had been dereliction of duty, for when confronted by a massive counter-attack by a dozen Chaos warbands drawn to the Iconoclasm's revolt, alongside an unknown number of degenerate Mutant hordes drawn from the edge-worlds of the sector, the Night Reapers had abandoned the Shrine World as both effectively indefensible and of "negligible strategic worth." Rather than allowing the world to fall, the Night Reapers turned their own weapons on the basilica-cities and granted the pilgrims and refugees who had sought harbour there a "merciful end." The rage of the Ecclesiarchy over this loss was boundless and ensured the Night Reapers Chapter's censure by the High Lords of Terra. Shorn of their Fortress-Monastery and Chapter homeworld and condemned to the perilous and thankless task of policing the outer reaches of the Laanah Rifts, the Night Reapers bore their punishment with grim impassivity and obedience but little contrition -- or at least appeared to. Within a standard decade, however, Imperial contact with the Chapter, which had long carried a reputation for ruthless efficiency, independence and technical aptitude, grew untowardly infrequent. Official contact ceased and such second-hand reports of them that could be gleaned pointed towards steadily increasing deviation from Codex Astartes doctrine, tactics and equipment in their ranks.
In 989.M41, some six standard years after the last Imperial contact, the Night Reapers were declared Excommunicate Traitoris after forensic examination of wreckage found in the Guyathis Belt provided incontrovertible evidence of the Chapter's direct responsibility for the destruction of the Rogue Trader fleet of Baron Stross Yuen. This followed a series of other raids and incidents where the involvement of the now-Renegade Chapter had been suspected, but firm enough evidence could not be found to blame them, while several Imperial expeditions to find the Night Reapers had disappeared without trace. The first Space Marines to respond to the call to find and punish the Night Reapers comprised a four-company strong force of the Avenging Sons Chapter who, alongside Imperial Navy support, set out into the Rifts in search of the Renegade Chapter. Responding to a distress call from the Imperial outpost on Svarga Wells, the Night Reapers ambushed the Avenging Sons and forced them into a humiliating retreat, capturing one of their Strike Cruisers, wrecking a second and badly mauling their would-be destroyers. The debacle of the Avenging Sons' defeat, which they blamed on the Night Reapers' use of unknown "Warp flame weapons" that bypassed their starships' Void Shields, moved the High Lords into direct action and two full Chapters of Space Marines, the Red Templars and the Minotaurs, alongside considerable local support from the fleets and defence forces of neighbouring sectors, were directly tasked with the destruction of the Night Reapers. This was to be done before their threat could grow further, lest they become a beacon to other Renegades and malcontents in an already troubled region.
The harrowing of the Night Reapers was to take a further three standard years of running battles to reach its fruition and it was a campaign in which, of the Imperial Chapters, the Red Templars, experts as they were in search and destroy and pursuit operations, were to be the hounds and the Minotaurs with their brute strength and aggression would be the hunter ready to deal the death blow. The Night Reapers fought with savage resistance across a dozen star systems and in a score of ship-to-ship battles as they were driven before the Imperials, bloodying their pursuers at every turn. It soon transpired that the Night Reapers, having thrown off the rule of the Emperor, had sought advantage in innovation, their Techmarines adapting xenos weapons technology originating with the cursed and near-extinct Hellgrammite race to their own ends, and their masters striking pacts with the servants of the Archenemy to further their cause.
From this the Night Reapers gained the strength to resist the Imperial onslaught for a time, but their relentless foes eventually cornered the bulk of the surviving Night Reapers at the Perun Cross -- a massive derelict pre-human space wreck large enough to have accrued its own thin atmosphere and parasitic life over the long ages. Here the Night Reapers were tunnelling into the ancient artificial core of the wreck, kilometres deep, in search of a weapon that they believed would be sufficient to rid themselves of the Imperial forces who now encircled and besieged them. Events as they transpired at the bitter point of the siege remain shrouded in confusion, but what is known is that at the height of the Minotaurs' attack, the Grey Knights Strike Cruiser Equinox Blade and a force of Grey Knights, under the command of Brother-Captain Danicus, arrived in orbit around the Perun Cross.
Entering the fire zone, they ordered the Imperial forces to concede to their authority and pull back from the assault; the Minotaurs, however, were not included in this course. The retreat of the Loyalist forces paved the way for Brother-Captain Danicus of the Grey Knights to conduct a teleport assault into the depths of the Perun Cross as the battle raged on. What then transpired remains unknown, but sometime shortly afterwards the Perun Cross' structure broke up into burning fragments, riven by a series of gigaton-level explosions. The demise of the Perun Cross led to the complete loss of the Grey Knights' strike force and a substantial, but undefined number of Minotaurs Space Marines, along with heavy damage to the Equinox Blade and the death of all those left on board.
Asterion Moloc, the stern Chapter Master of the Minotaurs, is known to have survived the incident as he was once again witnessed commanding his Chapter in battle some solar months later, while the Grey Knight Lords of Titan and the Ordo Malleus have remained curiously silent over their losses. As for the Night Reapers Chapter, it is believed that the fiery death of the Perun Cross served as the funeral pyre for this once-Loyal Chapter. Whatever profane secrets surrounded them are believed to have been buried there, as well.
- The Siege of Lakadamon (953.M33) - The Sons of Guilliman, alongside several Tekarn armoured regiments, are besieged in the defence of the Hive World of Lakadamon by the hordes of the Ork Warboss Vorhgad Bloodfang. Despite vastly overwhelming odds, the Chapter successfully holds the planet's defence for three standard years until the siege is broken by the combined forces of the Night Reapers and War Bearers Chapters, fighting alongside a major taskforce from Battlefleet Tempestus to break the orbital blockade that encircles the beleaguered world.
- The Constantinus Iconoclasm (981.M41) - The Adeptus Astartes Night Reapers are heavily censured after they abandon the Shrine World of Salvation-Gamma to the massed Chaos Space Marine and mutant forces closing in upon it, turning the guns of their gathered war fleet on the planet in order to grant the population what they consider a merciful end. The Ecclesiarchy lodges such vociferous objections with the Senatorum Imperialis that the Night Reapers are declared to have committed a gross dereliction of duty and, as punishment, are consigned to duty along the outer fringes of the Laanah Rifts. Within a decade, contact with the Chapter is almost entirely lost.
- The Perun Cross Incident (989.M41) - Having been conclusively linked to the destruction of the fleet of the Rogue Trader Baron Stross Yuen, the Night Reapers Chapter is declared Excommunicate Traitoris. The Minotaurs and Red Templars Chapters are despatched to track them down in the depths of the Laanah Rifts and bring them to the Emperor's justice. The harrowing of the Night Reapers drags on for three standard years, with evidence of the Renegades harnessing numerous forms of xenos technology amassing throughout. At length, the Night Reapers are cornered onboard a vast, pre-human void construct known as the Perun Cross as they attempt to mine some unknown but no doubt blasphemously potent weapon from its core. In the final assault, a Grey Knights strike force arrives and boards the Perun Cross, but events take a drastic turn as the construct, the entire Grey Knights force and a large number of Minotaurs squads are consumed together in atomic fire. It is assumed that the Night Reapers Chapter is no more, though Imperial forces stationed along the Laanah Rift remain vigilant for signs that any of the fallen brethren survived the Perun Cross incident.
- The Reapers at Bay (999.M41) - A reclamator fleet of the Renegade Night Reapers Chapter, thought destroyed earlier in history, is cornered by Inquisitor Celaeno of the Ordo Malleus in the bleak expanse of the Caligulan Nebula. With a full company of the Red Hunters Chapter at his command, spearheaded by the ancient Fellblade Tellum Veritatis, Celaeno forces a confrontation on one of the many barren worlds found in the nebula and is met by the Warp-tainted armoured vehicles of the Night Reapers. As the Tellum Veritatis duels with the daemon-touched Typhon Heavy Siege Tank Nidhoggr amid a plain strewn with the broken remains of battle tanks, Celaeno is slammed by an errant shell and the Red Hunters retreat, carving oaths of vengeance into the armoured flanks of Tellum Veritatis.
The Night Reapers' appearance is not listed in current Imperial records, but it is known that they utilised black, gold and purple colours on their battle-plate and vehicles.
The Night Reapers' Chapter badge was a large, unidentified golden animal skull, centered on a purple circlet in front of a pair of crossed golden coloured scythes.
- Imperial Armour Volume Two, Second Edition - War Machines of the Adeptus Astartes, pg. 17
- Imperial Armour Volume Twelve - The Fall of Orpheus, pp. 136-137
- Imperial Armour Volume Thirteen - War Machines of the Lost & The Damned by Andy Hoare with additional material by Alan Bligh & Neil Wylie, pp. 25, 47