>The Forgotten Apocalypse.

>There is an ancient myth attached to the cold and darkly fabled stars at the edge of the Segmentum Obscurus of an ancient war with no remembered name fought in the depths of the Imperium’s history. This war was unequalled in ferocity, and so terrible that every mention of it has been purged from the Imperial record, save perhaps for a few fragmentary references in most heavily restricted archives of the Holy Ordos, the cycles of certain Astartes battle sagas, and ancient Mechanicus data-canticles. This myth, discredited and dismissed by many pursuers of dark lore, has become an obsession of many among the Pheanonite faction. They seek both the possibility of supreme power and an apotheosis of their own desires in the ancient secrets left over from that war.

>Scattered fragments of stories hoarded by heretics and other apocryphal sources tell of a great and terrible conflict, erupting by some accounts in the mid of the 32nd Millennium, a legendary time of anarchy for the post-heresy Imperium. According to the legend, a strange artefact---a vast labyrinthine contrivance seemingly spun of dust and magnetism---was encountered by Explorators somewhere deep in the Halo Stars beyond what was then as the Calyx Expanse (though other sources place it in the dread Mandragora region or even as far a-field as the Unbeholden Reaches). This great and mysterious artefact they designated the ‘Echoing Vault.’

>This vast artefact—perhaps an embassy from an unknown realm of existence---unleashed a wave of horror never before seen on an unsuspecting and unprepared mankind. The xenoforms which mercilessly ravaged forth, if in truth they could be called such, were creatures of such abhorrent terror they are referred only obliquely in the records as ‘The Harrowing.’ These entities disobeyed known physical laws, and close proximity to them alone was enough to kill or drive the unprotected mind insane.

>The Harrowing mercilessly ravaged all in their path, and no force could stand against them. In a few short years, the deaths of a thousand inhabited spheres---both human and xenos---were laid at their feet, along with unprecedented losses for the Adeptus Astartes and the Inquisition lead forces trying fruitlessly to check them.

>According to a version of the legend favored by dark hereteks, ultimately the Holy Ordos found only a fusion of archeotech and sorcerous lore could hold the Harrowing so that the Imperium could strike; although at supreme risk to the Inquisitors that employed them. Suffering defeat, the Harrowing fled back across the carcasses of dead worlds to the Echoing Vault, where it is said the Mechanicus employed a forbidden weapon of the Dark Age of Technology to destroy their foothold and seal the breach between dimensions through which they had passed.

>So terrible was the conflict and its implications that afterward, all records of it were purged from Imperial histories, and its remaining traces all but lost in the turbulent years that followed. Some heretic adepts point to the sudden weakening of Imperial power in those long forgotten days and the vast deserts of lifeless worlds on the eastern Fringe as proof of the Echoing Vault’s existence. Most (including many in the Holy Ordos) scorn this legend as either outright fabrication, misinterpretation, or a lie designed to cover some other, darker truth. However, in more recent years, some within the Calixian Tyrantine Cabal have drawn parallels with this long discredited legend and the phenomena known as Komus, the Tyrant Star, whilst others instead favor different explanation of the myth---a mangled misinterpretation of a Chaos incursion, a short lived warp rift or even some long forgotten Tyranid precursor hive. Some few who know of the story wonder if somewhere in the vastness of their silent other realm, removed from both euclidean realspace and the empyrean seas of the warp, the Harrowing yet wait patiently for their hour to return.