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The Grail Abyss is a desolate streak of territory at the extreme northern border of the Imperium of Man. It is a celestial wasteland locked between two galactic spiral arms where stable star systems are scarce and rogue planets, energy bleed-outs, cosmic detritus and other navigational hazards are many. Sparsely populated and remote, it makes for one of the most dangerous regions of the Segmentum Obscurus.

With the more populous sub-sectors of the Cyclops Cluster and the Manachean Commonwealth, the Coronid Reach and the Mechanicum-controlled domain of the Cyclothrathine Holdfast, the Grail Abyss constitutes one of the regions of the wider Coronid Deeps.

Its history is closely linked to that of the famed 7th Expeditionary Fleet of the Dark Angels Legion of the Legiones Astartes under command of Lord Commander Suleiman Grimm. Indeed the 7th Expeditionary Fleet was responsible for the conquest and liberation of many worlds amongst the Grail Abyss and the Cyclops Cluster during the era of the Great Crusade.


Separated from the remote Coronid Reach Sub-sector by the mysterious and dreaded Coronid Prohibition Zone, the Grail Abyss lies to the galactic northwest of the heavily-populated worlds of the Manachean Commonwealth and to the galactic north of the Cyclops Cluster. The Grail Abyss forms the very edge of the Segmentum Obscurus and known space; beyond its borders lie only drifting star systems accessible to the vagaries of relatively stable Warp-passages from more coreward planets -- among these outer realms being such systems as the infamous Istvaan System or Ultima Ectosa, the furthest star to the galactic North known to possess an Imperial colony.

The Grail Abyss suffers from a psychic emptiness in local Warpspace, which has given it its name as travelling in this region compares to the exploration of the antique seas of sacred Terra. In conjunction with other stellar hazards, this phenomenon makes travel in the region unreliable and indeed more difficult than reaching more far-flung planets such as those of the Coronid Reach. As a result, human colonies within the Grail Abyss are few and far-flung, mere candle-points flickering in a sea of night.

All these difficulties however do not seem to have hindered human colonisation in the Dark Age of Technology, the Grail Abyss possessing advanced human settlements and worlds as developed and populous as those of the Cyclops Cluster. With the breakdown of communication and interstellar travel that accompanied the dawn of the Age of Strife, many of the worlds of the Grail Abyss regressed significantly, and some fell prey to unidentified cataclysmic events which still cause much puzzlement among Imperial savants.

Contrary to the more powerful worlds of the Manachean Commonwealth, the worlds of the Grail Abyss never suffered from the baleful intentions of the Mitu Conglomerate as it was by then firmly in the hands of the Orks who had colonised several planets. In the 30th Millennium, as the Great Crusade reached the northern marches of the galaxy, the Grail Abyss was mostly brought into the folds of the sprawling Imperium of Mankind through the efforts of the 7th Expeditionary Fleet lead by Lord Commander Suleiman Grimm of the I Legion which had already liberated great parts of the Cyclops Cluster.

The Coronid Deeps, of which the Grail Abyss is part.

During the events of the Horus Heresy, the Grail Abyss was somewhat spared the bloodier events or the devastation unleashed among the Cyclops Cluster as the Traitors never truly deployed in force in the region. Likewise, the Loyalists deployed very few forces in the Abyss as its worlds were considered too isolated and ultimately less important on a strategic level than those of the Cyclops Cluster and the Manachean Commonwealth. With only a finite amount of warships at its disposal, the Armada Imperialis preferred to focus on the defence of more strategically important worlds, and so the Grail Abyss was largely abandoned to its fate.

The isolation and Warp vagaries of the Abyss, however, caused it to become a ready refuge for fleeing Loyalist elements who had escaped the Massacre of Istvaan V. Having regrouped and in some cases even resupplied, these Loyalist splinter groups would mostly choose to flee to more defensible systems; however some would chose to remain and fight the Traitors like the grim Autek Mor of the Iron Hands Legion and his vessel, the Red Talon.

Planets of the Grail Abyss

  • Grail - This errant world that has long given the Abyss its name is now a Dead World. Who discovered the planet has been lost to history, but what is known is that it was given its iconic name by Rogue Trader Corthona van der Veld in 891.M30. Grail was obviously once teeming with life, harbouring billions of human citizens as the ruins of its continent-spanning hive-cities that are now silent as a tomb testify. Some past cataclysm has dissociated Grail from its native star and the world now follows an erratic orbit around a rogue star whose trajectory gradually takes it out into the intergalactic void. What event indeed caused the death of Grail's population is still a matter of conjecture, as there is no proof indicating why or even when the planet died. Part of the planet's atmosphere has frozen into what will eventually become a final winter once it has reached the intergalactic void where no starlight shines. Grail's surface has been scoured by radiations and its core is now almost entirely extinguished, bleeding its heat into the merciless void. It is likely that Grail would have remained one of an innumerable number of mysteries encountered during the Great Crusade's expansion and all but forgotten if it weren't for the fact that much of Grail's human technology has remained curiously and inconsistently intact. This has led Grail to be categorised as a Relic World, a place of hidden wealth where those lucky enough can make a fortune; therefore the planet has long drawn Explorators and would-be treasure-hunters and led them mostly to their death. However several STC remnants and numerous artefacts from Mankind's golden age were recovered from its ruins. Such explorations are highly dangerous, as aside from its inhospitable climate, Grail is extremely geologically unstable, which can result in the sudden and unexpected collapse of entire sections of its ruins. Lastly, there have been confirmed sightings of several non-indigenous xenos species and creatures that have either become stranded on Grail or are purposefully exploring its ruins. Reports of Psychneuein infestation -- while persistent -- have thus far remained unconfirmed.
  • Baroda - Baroda is a former Knight World, homeworld to the feared and much hated Knights of House Makabius, but has now laid dead for more than ten millennia. At its inception towards the end of the Dark Age of Technology, Baroda boasted the typical climate and saurid megafauna associated with such worlds. Wrecked by storms and confronted with its dwindling natural resources, the Knight Houses of Baroda descended into internecine war from which only the severely depleted Makabius would emerge. Having regressed to the point of the use of fossil-fuels, Baroda's rediscovery by the Imperium in 831.M30 contributed to the restitution of House Makabius as a fully-fledged Imperial Knight Household. However, its isolation in the Grail Abyss still served to keep it far from regular contact and influence.
  • Damaetus III/II - Another Knight World of the Grail Abyss, Damaetus III/II is the home "world" of the illustrious House Vyronii. Damaetus III is in fact the habitable moon of the green gas giant Damaetus II, a satellite of mist-shrouded forest and swamps dominated by the Knights' principal fortress, the mighty Felweather Keep. Home to highly intelligent and psychically gifted cephalopod-mammalian hybrid lifeforms that once tried to subjugate the human colonists but were eventually overthrown by the noble Knights, the world suffered from the expansion of the xenos empire known as the Mitu Conglomerate. The Knights of House Vyronii have remained stalwart defenders of the Imperium, even during the dark days of the Horus Heresy.
  • Hialis - Hialis was a Feudal World only recently contacted by the Imperium whose population would entirely succumb to a highly virulent and hence unknown plague during the early days of the Manachean War. The plague seemingly manifested itself spontaneously within a few short solar hours after the appearance of an unknown comet in the world's sky.
  • Keopsis - Distant Keopsis is a singular world that lies on the very edge of the Segmentum Obscurus, with only Zarnov further out on the Imperium's border. Keopsis is an ancient world with its inhabitants -- the Keopsar, as they refer to themselves -- believed to be descendants of the original population of the Dark Age of Technology. Orbiting its distant star, Urtal, Keopsis was a populous world, a proto-Hive World whose cities span over entire continents. This would, however, dramatically change when its star went hyper-active, frequently bathing the world in devastating solar storms. Scorched by cosmic rays and furance-hot solar blasts, the Keopsar -- who had maintained a considerable technological level throughout the Age of Strife -- had no other alternative than to descend beneath the earth and inhabit subterranean cities which extend for many kilometres underground. Adjusting to these new conditions, the Keopsar thrived, adapting to these new frequent calamities, building vast absorption towers to harness the solar energy and produce nearly limitless energy. Keopsis' surface can only be visited during brief planetary "solar winters" thanks to the extreme range of Keopsis' orbit around its star. During these winters the Keopsar venture forth from their underground cities to collect fresh water from coalescent steam and to evaluate the damage done to their surface workings and make emergency repairs. Keopsis was discovered during the later Great Crusade by the 7th Expeditionary Fleet of the I Legion, the Dark Angels. This event sparked a brief but intense civil war that was won by the pro-Imperial faction thanks to the aid of the sable-armoured warriors of the Legiones Astartes. With victory assured, Keopsis willingly entered the fold of the Imperium, serving as an important mining colony as its deep-core mines proved rich in rare crystal and mineral deposits. In exchange, Keopsis benefitted from the technologies of the Imperium, rejuvenating its own stagnating technology. Keopsis has since become a fully-fledged Hive World, a beacon of Imperial civilisation, a frontier outpost and the famed "last light" before the darkness at the end of known space. When the Horus Heresy broke out, the fighting was fierce, Loyalists and Traitors alike trying to find shelter underground before Urtal's fiery embrace scorched the earth clear of their presence.
  • Lascal - Lascal is a habitable star system situated at the edge of the Grail Abyss that has become a major Fleet Anchorage of the Segmentum Obscurus. Only two worlds are of importance within this system: the Imperial colony implanted on Lascal IV and the great Armada Imperialis Fleet Anchorage that was established in orbit around its neighbour Lascal V. Upon its discovery, Lascal was firmly held by Orks, necessitating a suppression-campaign by the forces of Lord Commander Suleiman Grimm of the 7th Expeditionary Fleet. After the extermination of the Orks, Lascal became a forward outpost of the Armada Imperialis which was quickly expanded by the arts of the Lucien Mechanicum. This intervention has led to lasting ties being established between the two worlds that persist to this day. Thriving upon the Great Crusade's needs, Lascal was properly colonised, its population entirely imported from other regions of the Imperium. As the Great Crusade turned away from the Grail Abyss, Lascal's tactical and strategic importance decreased and its Fleet Anchorage was heavily downgraded but eventually maintained as a link in the growing chains of Imperial authority. During the following decades, Lascal's native population slowly expanded to fuel its orbital industries and it became a self-sustaining world until in 902.M30 it was granted administrative independence with its own Imperial Commander. Though downgraded, the Fleet Anchorage still harboured a fleet, some forty ships-of-the-line and up to one hundred and twenty Escorts. Its real strength resided in a trio of Retribution-class Battleships, the Sceptre of Iron, the Ozymandias and the Star Tamer. This sizeable detachment would prove the first obstacle to the Traitors' rampage through the Coronid Deeps, Gethsamaine having fallen shortly before with little resistance. In 006.M31 Lascal was attacked by the entire Death Guard Legion which arrived suddenly and with overwhelming force. Quickly overrun, Lascal's sole contribution was to issue a last garbled warning of the Death Guard's arrival to the naval authorities at Port Maw and the Sub-sector capital world of Dominica Minor. When despatched ships of the Armada Ultima, in this case a squadron of deep-range Cruisers drawn from the XVII Sun Dragons, would later investigate that matter, they would discover a star system that had been murdered. The planets had been ravaged by radiation and fire and its near-space was choking with the debris of starfaring vessels, amongst them the hulls of the three mighty Battleships. The Armada Anchorage Point was now nothing more than another debris belt orbiting Lascal V and the once verdant world of Lascal IV was a toxic green and black poisoned orb that had succumbed to mass biochemical bombardment. Some locations like the Planetary Governor's palace had been sealed off swiftly enough not to succumb to the poisonous vapours and there the Death Guard had exacted a bloody toll on the defenders, utterly crushing them. Solar Auxilia landing parties would discover the bloated corpse of Lascal's governor impaled by a banner bearing the Death Guard's sigil above the cast-down Aquila. Other parties would report streets littered with corpses and spent Bolter-shells, which would lead the event to being widely called "the Murder of Lascal."
  • Shoar - Shoar is a Feral World of great repute located at the heart of the Grail Abyss and not too distant from Baroda. Whereas Keopsis is a world of fire, Shoar is a world of ice, a witheringly cold planet orbiting a bloated, dying star. Its population is only settled in the equatorial regions of the world and locked in perpetual inter-tribal warfare which have led Shoar's population to become phenomenal exemplars of human survival instinct and true warriors. In fact, several Solar Auxilia Cohorts of so-called "Skull Takers" drawn from Shoar have long been attached to the 7th and 60th Expeditionary Fleets. It is commonly believed that several intakes of tribesmen from Shoar have been sent to Terra to assess their genetic and cultural suitability for Space Marine conversion. However, results had still to be released before the outbreak of the Horus Heresy and no further action was ever taken.


  • The Horus Heresy - Book Four: Conquest (Forge World Series) by Alan Bligh, pp. 10-11, 24, 27-30, 70-71