Imperium of Man - Imperium Nihilus: Vast tracts of Imperial space lie beyond the roiling Warp storms that make up the Great Rift. Cut off from all but the most determined aid, blind to the Astronomican's light and beset upon all sifes by legions of nightmarish foes, the worlds of the Imperium Nihilus, the "Dark Imperium," must look to their own survival, by whatever horrific means necessary.The region of space known as the Imperium Nihilus is cut off from Terra's light by the Warp storms of the Great Rift. Not only is the light of the Astronomican obscured by these raging tempests, but there are also only two comparatively stable channels through which Imperial fleets are able to cross the storm front. Even these shuddering gauntlets are haunted by empyric phantasms and piratical wolf packs, but they are at least safer than the narrow passages that open sporadically between the storm belts only to sweep shut like a monster's jaws upon those brave or desperate enough to dare the crossing.Thus severed from the rest of the Emperor's realm, each world in the Imperium Nihilus must stand alone amidst the darkness. Many fell during the first nightmarish days of the Noctis Aeterna, when shock waves of psychic upheaval lashed the galaxy in the wake of the rift's opening. Planets and their populations were annihilated or twisted beyond recognition as Warp storms engulfed them. Hordes of Daemons spilled from rents in the fabric of reality to butcher and torment all before them. Heretical cults arose, prophesying the end of all things and whipping formerly loyal citizens into a murderous frenzy. Rampant mutation ran rife, abominations were spawned from the darkest nightmares of Human minds and entire populations turned on one another in self-destructive storms of violence and cannibalism.Other Imperial worlds held out. Fortresses rallied their garrisons, readied their weapons and drove back attackers from within and without. Hardy Agri-worlders formed defence militias, vanishing into the wilds and fighting guerilla wars against alien invaders. Industrial Worlds drafted every man, woman and child to churn out endless streams of materiel, hurling wave upon wave of conscripted soldiery into the teeth of terrors from beyond the stars.Even still, for many worlds death might have been the kinder fate. The Immaterium roils and churns, making Warp travel catastrophically perilous. Forced to wrestle with spiteful empyric tides, wildly erratic destination flux and dramatic temporal distortion, Imperial voidships in the Imperium Nihilus can risk only the shortest Warp jumps, meaning that not only is travel through the Imperium Nihilus terrifyingly dangerous, but it must also proceed at a virtual crawl. Interplanetary communication, too, has been almost entirely stifled; forcing an astrotelepathic message across the Imperium Nihilus requires herculean and often fatal effort, and even those missives that do make it to their intended recipients arrive in the form of recurring nightmares.Many worlds are wholly isolated, more than one population believing themselves the only surviving bastion of Human ciilisation in the galaxy. Many planetary governors, military commanders and religious leaders have been forced to make terrible choices and commit monstrous deeds in order to keep the lights of civilisation burning upon the worlds they rule. Plagues of mutation, madness and supernatural disease blossom while landscapes warp and change beneath baleful skies. Malefic entities manifest seemingly at will to prey upon the unwary, while simple despair stalks every Human soul. And always the Great Rift blazons itself across the firmament, corrupting all that its noxious light touches.Though the Human territories within the Imperium Nihilus are crippled, the same is not true of their enemies. Some xenos species possess alternate methods -- be they technological, biological or seeminglysorcerous -- by which they can traverse the stars while bypassing the Warp altogether. Others revel in the madness that has been unleashed, joyriding the currents of empyric madness wherever fate wills and falling in howling tides upon whatever worlds lie in their path.That which blights Imperial worlds, fleets and armies serves only to aid the  worshippers of the Dark Gods. Even as it churns in madness, the Warp sweeps these Heretics and Traitors along on favourable tides, more often than not bearing them to their destinations swiftly, if not safely. Surges of immaterial energies allow renegade psykers to enact unspeakable rituals that drag entire worlds into damnation or translocate them into the hellish heart of the Warp. Ancient and terrible beings not seen abroad in millennia feed off the raw energies of unbridled chaos, gathering the strength to force their way through the veil and fall upon Humanity with howls of glee. Everywhere hope fails.Still the Loyalist worlds of the Imperium Nihilus fight on, shoring up their faltering hope with unbridled hate. For every star system swallowed by the darkness, a crusade blazes a trail across the stars to relieve the desperate defence of another. Space Marine Chapter planets, Inquisitorial fortresses and Adepta Sororitas preceptories shine as bright beacons of defiance amidst the shadows. Knight Worlds light their watch fires and weather the storm, just as they did during the dread millennia of Old Night.Meanwhile, daring Rogue Traders, dogged Adeptus Mechanicus Explorator fleets and courageous Imperial Navy flotillas brave the tumult of the Immaterium to bring hope to lost worlds or claim new colonies for Mankind. Perhaps the end of the galaxy draws nigh. Perhaps the darkness of the Imperium Nihilus will spread like a funeral shroud over all of Humanity's endeavours. However, while faith continues to burn strong in the hearts of men and women, the defenders of the Imperium will not give in.Perhaps this hope has been rewarded. When the Indomitus Crusade of Roboute Guilliman arrived to aid the Blood Angels Chapter and their successors against the horrors of Hive Fleet Leviathan during the Devastation of Baal, Guilliman appointed the Blood Angels' Commander Dante as the new regent of Imperium Nihilus. All the sons of Sanguinius now fight to reclaim the Dark Imperium from those who would defy the will of the Emperor.