Note: All dates from this point forward are provisional due to errors in the Imperial Calendar, meaning these events could actually have occurred at any time from the early 41st Millennium to the early 42nd Millennium.

  • Unknown Date.M42 Chaos Ascendant - In the wake of the fall of Cadia during the 13th Black Crusade and the birth of the Great Rift, a wave of Warp Storms roars into being across the length of the galaxy. Astropaths everywhere fear to open their minds to receive or broadcast messages, for the Immaterium rings with mind-splitting peals, possibly the sound of the myriad tears ripping open in the barrier between the material universe and the Warp, or perhaps the laughter of the Dark Gods...
  • Unknown Date.M42 The Noctis Aeterna - The Noctis Aeterna, also known as the "Blackness" in Low Gothic, was a catastrophic event which consumed the Milky Way Galaxy and the Imperium of Man beginning in 999.M41 and lasted at least into the second century of the 42nd Millennium. The Blackness began following the fall of Cadia at the climax of the 13th Black Crusade and the eruption of the Great Rift that cut the Imperium in half, and was marked by the loss of access to the Astronomican for FTL navigation and a disruption in all astrotelepathic communications. This period saw more devastating events consume the increasingly isolated worlds of the human-settled galaxy than at any time since the Age of Strife. Such was the turmoil during the creation of the Great Rift and the period following it that there could be no reliable accounts. As limited communications returned, Historitors and Chronotechs struggled to understand incoming reports. With the influx of Warp energies into such vast regions of realspace, time passed strangely, speeding up in some sectors, slowing in others compared to the sidereal time experienced on Terra, at the heart of the Imperium. These effects on the Warp from the birth of the Great Rift faded with the passage of time, allowing for the reestablishing of interstellar communications with some regions and somewhat more reliable Warp travel. This restoration of stability, combined with the onset of the Imperial counteroffensive known as the Indomitus Crusade, restored the grip of the Emperor over the Imperium once more. However, the price paid proved steep. Slightly less than half of the one thousand Space Marine Chapters known to operate across the galaxy remained unaccounted for, and no less than twelve Space Marine Chapter homeworlds were reported as destroyed during the Noctis Aeterna and the equally bitter campaigns that followed.
  • Unknown Date.M42 The Golden Throne is Failing - The Adeptus Mechanicus discovers that the Golden Throne has irreparable flaws that could ultimately endanger the Emperor's life. Despite the Adeptus Mechanicus' best efforts, its systems continue to fail, and no one still living knows how to repair them. Perceiving such dangerous ignorance as a manifest threat to the Emperor's safety -- and thus falling beneath the purview of the Adeptus Custodes -- Shield-Captain Heraclast Vadrian consults with Captain-General Trajann Valoris and receives permission to seek a solution. He gathers a band of his finest warriors aboard the Cruiser Scion of Argo, and sets off following a lead that points to the lost Forge World of Morvane.
  • ca. 999.M41-111.M42 The Indomitus Crusade - The Indomitus Crusade, led by Lord Commander of the Imperium Roboute Guilliman is waged against the surging forces of Chaos and the threats of myriad xenos such as the Orks, Tau and Eldar in the wake of the fall of Cadia during the 13th Black Crusade. Its purpose is to defend and reclaim those regions of the Imperium of Man lost in the wake of the massive tear in reality, the Great Rift, which sunders the Imperium in two, and the subsequent dire period of history known as the Noctis Aeterna.
  • ca. 999.M41 - Unknown Date.M42 Devastation of Baal - After sacrificing the Shieldworlds of the Cryptus System to fend off the xenos' earliest advance on the Baal System, the planet of Baal itself came under intense attack by Hive Fleet Leviathan. The Tyranid Hive Fleet was of such mass, even after its considerable losses, that it blotted the stars from the skies. Lord Commander Dante bolstered the formidable defences of the Blood Angels' homeworld and its moons like never before. Not one to await attack, he also sent forth scores of preemptive strike forces to delay, mislead, and whittle down the living armada. Hundreds of splinter fleets were thus defeated. Dante's call, beseeching the Blood Angels' Successors to send immediate aid to their parent Chapter, did not go unheeded. The Flesh Tearers were the first to arrive, and ultimately all the Successor Chapters save the Lamenters answered the call. Even the Knights of Blood, who had been declared Excommunicate Traitoris by the High Lords of Terra, arrived to bolster the defences. It was still not enough. Learning at an exponential rate, Hive Fleet Leviathan could not be thwarted by the same strategy twice. Advancing steadily, their superior numbers cleared the entire surrounding sector of life before the xenos made planetfall upon Baal and her twin moons. The first nineteen waves, each larger than the last, were driven off at great loss to the Blood Angels and their Successor allies. Five Chapter Masters fell in that bitter fighting, three in the Battle at the Dome of Angels alone. The Tyranids began the process of absorbing all biomass from Baal and its moons, absorbing even the radiation-poisoned deserts of Baal Secundus. With their defences in ruin and Baal's moons stripped and broken, the remaining Space Marines retreated back to the rubble of the Blood Angels' sprawling fortress-monastery. There, they prepared for a last stand as the next wave swept downwards. Doom, it seemed, had at last come to the Sons of Sanguinius. It was then that the Great Rift cracked open the galaxy in the wake of the fall of Cadia to the 13th Black Crusade, and the withered Baal System was blasted by the aetheric storms. Although no further attack waves came from the Leviathan Hive Fleet, not a single Imperial defender remained alive upon the last moon, Baal Prime. On Baal itself there were already enough Tyranids there to destroy the Imperial troops many times over. Even with no chance of victory, Commander Dante led his troops, each fighting retreat seemingly more hopeless than the last. As the final perimeter was broken, the stars reappeared. Looking skywards, the Tyranids on the surface of Baal sought contact with their Hive Fleet, but it was gone, replaced by a newly arrived Imperial fleet. Like an angel of vengeance came Roboute Guilliman and his Indomitus Crusade. After many more battles, Baal was finally cleared of the xenos threat. A great rebuilding of both world and Chapter was undertaken, for the Blood Angels and their Successors were sorely needed elsewhere in the beleaguered Imperium. What became of the Leviathan is a mystery, although a clue was found upon the now-barren moon of Baal Prime. Xenos skulls were piled impossibly high in the much-reviled, eight-pillared symbol of one of the Blood Angels' most terrible and ancient nemeses: the Bloodthirster Ka'Bandha and his army of Khornate daemons.
  • Unknown Date.M42 Into Shadow - Upon the direct orders of Captain-General Trajann Valoris, a small, fast-moving force of Custodians makes haste for the ruined remains of Cadia. Details of their mission are suppressed, even amongst their comrades, but they are accompanied by a number of warriors drawn from the ranks of the Shield Host known as the Shadowkeepers.
  • 001-025.M42 War of Beasts - The strategically located Hive World of Vigilus linked the Imperium Nihilus with the Imperium Sanctus through the Nachmund Gauntlet, one of the only known stable passes through the Great Rift. Realising the importance of this planet to the survival of the Imperium, it was assaulted by multiple xenos and Chaos forces, including the Black Legion under the command of Abaddon the Despoiler. Though the Despoiler's invasion was ultimately defeated by warriors drawn from multiple Space Marine Chapters under the command of the Ultramarines Chapter Master Marneus Calgar, Vigilus remained a world largely under siege from Ork, Drukhari and Genestealer Cult factions.
  • Unknown Date.M42 The Beast Hunters - Hive Fleet Leviathan and the remaining splinter fleets from the earlier invasions of the Milky Way Galaxy by Hive Fleet Behemoth and Hive Fleet Kraken, continue to assault myriad worlds of the Imperium, slowly making their inexorable way towards Terra and the gleaming psychic beacon calling them like moths to a flame that is the Astronomican.
  • Unknown Date.M42 The Fourth Sphere Expansion is Lost - The T'au Empire's Fourth Sphere Expansion is lost in the Imperium's Eastern Fringes soon after its inception due to the effects of the Noctis Aeterna and the spiraling Warp Storms that afflict the galaxy following the birth of the Great Rift.
  • Unknown Date.M42 Rise of the Undying Legions - The Necrons continue to awaken at a rapidly increasing pace on their Tomb Worlds across the galaxy, ready to rebuild their ancient interstellar empire, and wipe away all the "lesser races" that stand in their way.
  • Unknown Date.M42 Talledus War - The Talledus War was a War of Faith fought in the Era Indomitus between the forces of Chaos and the Imperium of Man to defend the Shrine World of Benediction in the Talledus System of the Veritus Sub-sector. Though Benediction was the Chaos forces' primary target, all the inhabited worlds of the system faced a large-scale assault led by the Dark Apostle Kor Phaeron of the Word Bearers Traitor Legion. The Word Bearers, as always, sought to convert the bulk of Humanity to the service and worship of the Chaos Gods. They took great pleasure in furthering this agenda by attacking a world and system that was of such importance to the Imperial state religion that they deemed a fraud. The fall of Talledus and Benediction to Chaos, and the conversion of its people to the true faith of Chaos, were deemed a potentially major milestone in the Word Bearers' plan to throw down the Corpse God of the Imperium and claim Mankind for the Dark Gods. The war proceeded on three fronts, on Benediction, on the Astra Militarum Fortress World of Ghreddask and in the void surrounding the asteroid belt called the Tears of the Emperor at the very edge of the system. On Benediction, the Word Bearers forces commanded by Kor Phaeron nearly seized control of the Grand Honorificum cathedral-city complex. The Loyalists were saved by an unusual phenomenon that was part of the Psychic Awakening when the faith of those gathered in the cathedral summoned forth from the Warp the protective spirits of the sacred Imperial dead. This supernatural force, later remembered as the "Saints' Wall," surrounded the Grand Honorificum in a protective psychic shield and extinguished the grip on reality held by many of the daemons making up Kor Phaeron's attacking army. This miracle allowed a demi-company of Salamanders Astartes to cut the remaining force of Chaos troops in two and establish a new defensive perimeter for the cathedral complex. On Ghreddask, the intervention of a Black Templars strike force destroyed the Soul Harvester mobile fortress-factory that had left the Imperial defenders at a loss, though the suicidal counterassault cost the life of the Astartes commander, Castellan Dramos. In the void, within the Tears of the Emperor, a piratical Night Lords fleet commanded by the battleship Nightmare of Celyx sought to draw in Imperial military and commercial shipping translating into the system from the Warp by using captured Imperial astropaths to throw off their Navigators' abilities. The Night Lords then took the spoils and reaped with great pleasure the terror of their victims. The arrival of Vanguard Marines from the White Scars' 10th Brotherhood turned the tables on the Heretic Astartes pirates. Their hit-and-run strikes soon transformed into a vicious, void-based guerilla war as each side tried to lure the other into ambushes. The White Scars succeeded in blunting the Night Lords' attacks on incoming Imperial shipping, but were unable to annihilate the Chaos raiding force entirely. Though the Imperium has so far managed to blunt the Chaos assault on the Talledus System on every front, the conflict is far from over.
  • ca. 005.M42 Ciaphas Cain Publishes Personal Memoirs - The famous Imperial hero, Commissar Ciaphas Cain publishes his personal memoris, To Serve the Emperor: A Commissar's Life. In his later years, Cain wished to gather and write a full accounting of his long and distinguished career. However, his more personal and candid memoir never sees the light of day and is put under Inquisitorial seal by the order of Inquisitor Amberley Vail. His personal archives contain far too many sensitive and restricted information. Undertaking the monumental task of organising Cain's files into a vast archive, she names it the Cain Archive, and publishes it for Inquisitors only. Many Inquisitors read Cain's candid accounts. Inquisitor Amberley is later persuaded to expand it considerably, making it somewhat of a bestseller amongst the agents of the Inquisition.
  • ca. 012.M42 Battle of Herodian IV - The Mantis Warriors, augmented by an Imperial Navy taskforce, comes to the aid of the beleaguered world of Herodian IV that is under attack by a large Tyranid Splinter Fleet. Despite taking a high number of casualties, the Imperials begin to turn the tide of the battle against the horde of bioform horrors, when Inquisitor Lord Brutius Parthon orders the Mantis Warriors to undertake an Exterminatus of the fallen world. This was carried out only after a Deathwatch Kill-team was extracted from a hidden Ordo Xenos weapons laboratory on the surface of the doomed planet.
  • ca. 037.M42 Cain Archive First Expanded - Orten Bassit publishes The Return of the Liberator: Ciaphas Cain and the Second Siege of Perlia. This book is later incorporated by Inquisitor Amberly Vail and used as an extract within the Cain Archive.
  • ca. 085.M42 Cain Archive Second Expansion - Stententious Logar publishes Purge the Guilty! An Imperial Account of the Liberation of Gravalax. It is later utilised by Inquisitor Amberly Vail and incorporated as an extract within the Cain Archive.
  • ca. 087.M42 Cain Archive Third Expansion - Nelson Lawford publishes Just Visitin': The Life of a Naval Hero, a biography of retired Imperial Navy Commodore Hubert Visiter. It is later utilised by Inquisitor Amberly Vail and incorporated as an extract within the Cain Archive.
  • ca. 095.M42 Cain Archive Fourth Expansion - Arten Burrar publishes The Abominable Chitin: A Concise History of the Tyrannic Wars. It is later utilised by Inquisitor Amberly Vail and incorporated as an extract within the Cain Archive.
  • ca. 097.M42 Cain Archive Fifth Expansion - Retired Lady General Jenit Sulla publishes Like a Phoenix From the Flames: The Founding of the Valhallan 597th. It is later utilised by Inquisitor Amberly Vail and incorporated as an extract within the Cain Archive.
  • ca. 101.M42 Cain Archive Sixth Expansion - Retired Lady General Jenit Sulla publishes Like a Phoenix On The Wing: The Early Campaigns and Victories of the Valhallan 597th. It is later utilised by Inquisitor Amberly Vail and incorporated as an extract within the Cain Archive.
  • ca. 111.M42 End of the Indomitus Crusade - Roboute Guilliman calls for an end to the Indomitus Crusade following the epic final battle for the Pit of Raukos. The Battle of Raukos is a two-pronged assault upon the world of 108/Beta-Kalapus-9.2 and the Warp rift known as the Pit of Raukos in Wilderness Space. The Loyalist forces quickly overwhelmed the allied Traitor Legions -- including the Word Bearers, the Iron Warriors and the Black Legion -- using the strategic location of the Warp rift to carry out assaults upon the surrounding Imperial worlds. This victory marked the end of the Indomitus Crusade and the start of Guilliman's involvement in the Plague Wars.
  • ca. 111.M42 The Plague Wars - The Plague Wars are a series of battles that occurred within the Realm of Ultramar between the forces of Nurgle, led by the Daemon Primarch Mortarion, and his Death Guard Traitor Legion against the Ultramarines, their Successor Chapters and other Imperial forces. This conflict began following the events of the 13th Black Crusade and the opening of the massive Warp rift known as the Cicatrix Maledictum. By ca. 111.M42, over a hundred standard years after the start of the Indomitus Crusade, the Imperial defenders all across Ultramar were depleted in dozens of ground campaigns, while a Plague Fleet systematically destroyed the realm's Ultramar Defence Fleet and star fortresses. Guilliman returned from the Indomitus Crusade after over a standard century of campaigning to stabilise the Imperium, and his deft and defensive manoeuvres bought time to launch what became known as the "Spear of Espandor" counterattack. The combined plague armies were eventually fought to a standstill amongst the ruins of Iax, before the Daemon Primarch Mortarion escaped with his forces back to the Scourge Stars under cover of a Virus Bomb attack, both because of his brother's staunch defence and because Nurgle's realm in realspace had come under assault by the forces of the Blood God Khorne. In a brief respite from the work of safeguarding the Emperor's realm after Mortarion's defeat, Guilliman ordered the rebuilding and decontamination of Ultramar, as well as the establishing of new procedures for creating further Primaris Ultramarines. It was not long before new Imperial Crusades called the Lord Commander of the Imperium away from Ultramar and back out into the dark galaxy. The Ultramarines then began the work of preparing their vengeance against the servants of the Dark Gods.
  • ca. 127.M42 Cain Archive Seventh Expansion - Ayjaepi Clothier publishes In Blackest Night: The Millennial Wars Appraised. It is later utilised by Inquisitor Amberly Vail and incorporated as an extract within the Cain Archive.


  • Codex Adeptus Astartes - Space Marines (8th Edition), "A Brotherhood at War," "Chronicles of Ultramar," pp. 18-19, 29
  • Codex: Adeptus Custodes (8th Edition), "The Tale of the Ten Thousand," pp. 32-33
  • Codex Heretic Astartes - Chaos Space Marines (8th Edition), "A Legacy of Hate," pg. 25
  • Gathering Storm - Part II - Fracture of Biel-Tan (7th Edition), "Addenda Inquisitoria", pg. 18
  • Warhammer 40,000: Rulebook (8th Edition), pp. 50-53
  • Warhammer 40,000: Rulebook (7th Edition)
  • The Fall of Medusa V (2006 booklet)
  • Medusa V Archive
  • Warrior Brood (Novel) by C.S. Goto
  • Kill Squad - A Deathwatch Omnibus (Omnibus) by Various Authors
  • Ciaphas Cain Series:
    • For The Emperor (Novel) by Sandy Mitchell
    • Cain's Last Stand (Novel) by Sandy Mitchell
    • Duty Calls (Novel) by Sandy Mitchell
    • The Traitor's Hand (Novel) by Sandy Mitchell
  • Dark Imperium (Novel) by Guy Haley
  • Devastation of Baal (Novel) by Guy Haley
  • Imperium Nihilus - Vigilus Defiant (8th Edition), pp. 5-20
  • Psychic Awakening: Faith & Fury (8th Edition), pp. 8-19

M41 Timeline Finis
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