Grim Dark Lore is the name of several series of Warhammer 40,000 lore videos on YouTube created by video production company Raven Rock Entertainment in conjunction with the Warhammer 40,000 Wiki. The series debuted on Monday, April 20, 2020, and new episodes will air every week thereafter.
The series chronicles the entire history of the Warhammer 40,000 universe, from Humanity's first steps into the void, through the Horus Heresy, the long years of Imperial stagnation and finally the birth of the Great Rift and the glorious resurrection of Roboute Guilliman!
Warhammer 40,000 Overview Series
To see the entire series please see the Grim Dark Lore Playlist.
A short teaser trailer announcing the start of Raven Rock Entertainment's flagship lore video series, "Grim Dark Lore."
Grim Dark Lore 1: Exodus
In this first video in the series, the chronicle of the Warhammer 40,000 galaxy begins! From Humanity's first steps out into the void, through the settlement of Mars and other worlds using the Long March generation ships, to the discovery of the Immaterium and the development of Warp-Drive, explore the Age of Terra and the dawn of the Human golden age!
Grim Dark Lore 2: Golden Age
The Warhammer 40,000 galaxy's golden age! Explore the apex of the first Human interstellar civilization during the Age of Technology as it reaches extraordinary heights of science and technology and makes first contact with other alien species such as the Aeldari and the Orks.
But hints of the grim darkness to come appear on the horizon with the emergence of the first, true Human psykers.
Grim Dark Lore 3: Old Night
First to herald doom was the birth of Human psykers, whose inability to control their powers and avoid possession by Warp entities led to massive destruction across the galaxy. Then Humanity's thinking machines turned on their creators. Next was the complete disruption of Warp travel caused by growing instability in the Immaterium.
Cut off from one another, the worlds of Mankind soon descended into anarchy, ignorance and constant war. Even Old Earth, the jewel of Human civilization, was transformed into a post-apocalyptic wasteland. But one man, Malcador the Sigillite, was determined to find salvation for Humanity...
Grim Dark Lore 4: Rise of the Emperor
An unknown warlord known only as the Emperor emerges onto the stage of the Warhammer 40,000 galaxy. During his search for Human salvation on Terra, Malcador the Sigillite discovered the man known only as the Emperor, and that he had a plan for the salvation of Humanity from the horrors of the Age of Strife.
In pursuit of that hope, the Emperor took up residence in the Sigillites' old Himalayan fortress and began the production of his potent genetically-engineered honour guards, the Legio Custodes, and his future army generals, statesmen, and genetic sons, the Primarchs. But before his quest could even begin, the Great Enemy struck first...
Grim Dark Lore 5: Unity
The Unification Wars erupt across Terra as the Emperor of Mankind begins his quest to unite the Warhammer 40,000 galaxy. Despite the loss of the Primarchs, the Emperor is determined to save Humanity from the anarchy of the Age of Strife.
Despite their martial strength, the Thunder Warriors prove to be deeply flawed and ultimately turn on their creator. They are wiped away by their successors, the Emperor's ultimate gene-forged warriors and angels of death, the newborn Legiones Astartes, the Space Marines.
The Space Marines complete the Unification of Terra while the Emperor lays the foundations of a new civilization on Humanity's homeworld.
Grim Dark Lore 6: Lords of Mars
Mars had once been a jewel of the Human-settled galaxy, the heart of much of Humanity's technological innovation and scientific achievement during the Age of Technology. But the Age of Strife swept away the original Martian civilization in a post-apocalyptic tide of robotic rebellions, civil war, and ecological collapse.
From the ashes emerged a new civilization known as the Mechanicum, dedicated to an austere and strange religious faith in the deity they called the Machine God. Its leaders, the cybernetic tech-priests, reclaimed the Red Planet and built a new Martian culture dedicated to the pursuit and recovery of ancient knowledge...no matter the cost.
Grim Dark Lore 7: The Machine God
With the birth of the ancient Mechanicum, a new theocracy dedicated to the service of the Machine God arose from the post-apocalyptic ruins of Mars. But this deity demanded that its servants seek out knowledge wherever it could be found, and this necessitated the creation of tools to embody its will.
These were found in the various servants of the tech-priests, including the machine slaves called servitors, cybernetic Skitarii soldiers, Knight combat walkers and the great god-machines known as Titans. These creations not only served the will of the Machine God but also allowed its worshippers to come as close as they could in life to a spiritual union with the machine.
The Mechanicum next began to explore the galaxy despite the persistent Warp Storms, establishing by skill or luck new Forge Worlds dedicated to their faith across the galaxy. But the rise of the Emperor on Terra soon caught the tech-priests' attention, and many wondered if He would prove to be friend or foe...
Grim Dark Lore 8: Imperium
With Unity brought to Terra, and the Warp Storms of the Age of Strife finally clearing, the Emperor needed the resources and technical skills of the Mechanicum to make real His dream of a Great Crusade to restore the galaxy to Humanity.
He made the first move, going to Mars to propose a deal to the tech-priests. In return for their technology and manufacturing capabilities, he would restore to them Navigators, grant them autonomy and protection for their religion, and offer them the opportunity to search the galaxy for lost technology. It proved an offer too good to refuse.
With the empires of Terra and Mars reunited, a new state took shape -- the Imperium of Man. The Emperor used the aid of the Martian priesthood to build the ships and armies that would retake the galaxy for Humanity while He constructed the Astronomican to guide His fleets out into the void. Then the first test for the new crusade came in the outer reaches of the Sol System...
Grim Dark Lore 9: Fall of the Aeldari
The end of the Age of Strife was marked by a great flash of light seen across the galaxy. Within days of this event, the Warp Storms which had isolated the worlds of the galaxy for thousands of years at last began to dissipate, allowing the Emperor to begin His Great Crusade.
But the cause of that flash was the birth within the Immaterium of a terrible new entity of amoral hedonism called Slaanesh, the Dark Prince of Chaos. The price for the birth of the youngest of the Chaos Gods was nothing less than the near-extinction of the once immortal race known as the Aeldari.
The Aeldari had ruled a vast empire that was the technologically most powerful of the starfaring peoples of the Milky Way Galaxy. But eons of excess and the uncontrolled pursuit of dark pleasures had slowly twisted their once great civilization into something horrific.
Such wanton ways had slowly gestated a dark new being within the Empyrean. In one brief moment almost the entirety of the Aeldari species was eradicated by the psychic birth scream of this entity, which also created the great Warp rift called the Eye of Terror.
Yet some of the Aeldari survived, slowly evolving into distinct new factions -- Exodites, Craftworld Asuryani, Drukhari and Harlequins -- whose lifestyles differed based on their own adaptations to avoid the pull of Slaanesh upon their souls.
The Aeldari would prove to be both great foes of the newborn Imperium of Man as well as the strongest allies Humanity would ever know in the war to come against Slaanesh and its corrupt kin, who hungered within the Warp for the souls of Mankind...
Grim Dark Lore 10: Gods and Daemons
The Chaos God Slaanesh was born of the Aeldari species' uncontrolled hedonism and amoral pursuit of every excess and pleasure. But Slaanesh was not alone in the Warp. Three other Ruinous Powers existed to plague Humanity and all of the other sentient races of the galaxy -- Khorne, Nurgle and Tzeentch.
Khorne is the Blood God, the deity of wrath and murder. Nurgle the Plague Lord is the patron of despair and disease. Tzeentch is the Lord of Change, the champion of change, sorcery and knowledge. Together with Slaanesh, the Dark Prince of Chaos, they represented the Great Enemy to the Emperor's plan to reunify Humanity.
The Chaos Gods, aided by their daemonic servants and mortal cultists, saw the birth of the Eye of Terror as their greatest window on a mortal world they had long hungered to add to their own dominions. They would break down the barriers between reality and the Warp, until all of Creation had been subsumed within the Immaterium, just like the worlds of the lost Aeldari Empire.
Among his fractious kin, Tzeentch was the first to see the true danger the Emperor represented, an attempt to cut Humanity off from the Warp and starve the Dark Gods of the psychic energy they needed to survive and thrive.
And so the Lord of Change united his brethren to steal away the Master of Mankind’s children, the Primarchs, and scatter them across the galaxy.
But the Emperor would not be deterred, and launched his Great Crusade without them, hoping against hope that he might yet meet his sons again among the stars...
Grim Dark Lore 11: Great Crusade Begins
As the Warp Storms of the Age of Strife cleared, and Terra and Mars were successfully united under the aegis of the Emperor's Imperium of Man, the Master of Mankind's Great Crusade to reunite the Human-settled galaxy could begin at last. But none knew what awaited the great fleets in the void beyond Sol.
The purpose of the Great Crusade was to first and foremost forever banish the horrors of Old Night. Civilization was to be restored to the galaxy as it had already been on Terra and Mars. Logic and reason would serve as the foundations of a new golden age.
To this end, the Emperor established a new bureaucracy for the Imperium, embodied in the War Council that directed the course of the crusade with the aid of the reestablished Navigator houses. Any newly conquered worlds were made compliant with the atheistic doctrine known as the Imperial Truth, while all psykers were collected to be returned to Terra on the Black Ships of the Astra Telepathica and any unfriendly xenos species were exterminated outright.
Among the greatest servants of the Great Crusade were the Rogue Traders Militant who served as outriders of the crusade's many expeditionary fleets. It was a Rogue Trader who rediscovered the Knight Worlds of Humanity's lost Age of Technology, and restored the power of their Knight walkers to the arsenals of both the Imperium and the Mechanicum.
The Mechanicum was also strengthened enormously by the reestablishment of contact between Mars and the many Forge Worlds it had settled blindly in the void during the millennia of Old Night.
Perhaps the greatest discovery of the Great Crusade's early decades came on the world of Pentacanaes when a plague of rogue psykers led to the discovery of a group of women with the ability to defeat even the worst entities vomited forth by the Warp – though the price of this power included their own souls.
Finally, the crusade came to the dying mining world of Cthonia, and there discovered an individual who would have a greater impact upon the course of the Great Crusade than even the Emperor. His name was Horus...
Grim Dark Lore 12: The Son of Strife
As the Great Crusade reached out into the void, the Emperor of Mankind unexpectedly discovered one of his lost sons, one of the primarchs, on the mining world of Cthonia only a few light years from Terra. This was Horus Lupercal, who had been raised among the vicious gangs of Cthonia .
After being taught Imperial ways and learning of his father the Emperor’s mission to reunite the scattered worlds of Mankind, Horus gladly made the cause his own. He became the master of the XVI Legion of Space Marines, the Luna Wolves, and for thirty years fought at the Emperor’s side.
During this time, the character and culture of the Luna Wolves Legion began to slowly change, as its ranks of Terran-born Astartes were slowly replaced with Cthonians modeled in Horus’ own image. Out among the stars, Horus and the Emperor saved each other’s lives countless times and forged a uniquely close emotional bond.
But Horus had learned many lessons on Cthonia, the most important of which that no matter how great you were, there was always someone who sought to claim what was yours. When Horus learned that his father had discovered yet another of his Primarchs, he was happy that he was no longer alone…and secretly feared the emergence of a new rival for the Emperor’s affection. And Horus Lupercal was determined that no one would ever claim his rightful place in the sun.
Grim Dark Lore 13: Lost and Found
After three decades spent reuniting the human-settled galaxy at the side of his gene-son Horus during the Great Crusade, the Emperor of Mankind discovered two more of his missing primarchs, Leman Russ and Ferrus Manus.
Leman Russ was discovered on the barbaric Death World of Fenris, the king of a barbaric culture. The Emperor was forced to engage in a series of contests of strength and skill to earn the Wolf King's trust.
Russ became the master of the Space Wolves Legion, who had evidenced a startling disregard for all military discipline before their primarch taught them a new way to wage war. The Space Wolves soon became the Emperor's most trusted executioners, the Space Marine force who most embodied the savage aspects of his iron will.
The Emperor came to Ferrus Manus on the geologically unstable world of Medusa. Ferrus was a hard man, who was dedicated to the elimination of all weakness in both himself and his people. Only after engaging the Emperor in a titanic duel in which he finally met someone else who was a match for his godlike abilities did Ferrus swear allegiance to the Imperial cause.
The Iron Hands were reshaped by Ferrus into a Legion that also sought to eliminate all weaknesses in themselves, even if this required the replacement of their own flesh with the purity of the machine. Ferrus and his X Legion became masters at the use of armored forces and advanced technology in crushing the foe. They ultimately formed an unusually close bond with the tech-priests of the Mechanicum.
Ferrus joined Horus and the Emperor in helping to command the fleets of the Great Crusade, whose forces had now grown large enough to split into three major fleets. More primarchs were subsequently discovered and the Great Crusade continued to reach ever deeper into the galaxy.
Grim Dark Lore 14: A Thousand Sons
The XV Legion of Space Marines, the Thousand Sons, had been raised by the Emperor to serve as the Imperium's psychic weapon. But the Thousand Sons' demonstrated psychic abilities often made the other Legions uneasy, as they disliked psykers as much as the rest of Humanity.
On the world of Bezant, the Thousand Sons encountered a powerful psychic enemy that forced them to push their psychic powers to the limit. The result was a sudden and unexpected rampant mutation known as the "flesh-change" that afflicted one of the Thousand Sons. Soon, this mutation was spreading like wildfire through the XV Legion. Unless a cure could be found, the Thousand Sons might go extinct.
It was at this time that the Emperor came to Prospero and discovered Magnus the Red, one of his missing sons. Magnus had come centuries before to Prospero, a world that had recovered from a vicious infestation of psychic psychneuein parasites to create a new society based in the Tizca, the City of Light. The Prosperines were dedicated to the pursuit of psychic powers and knowledge about the Warp.
Reunited with his Legion, Magnus looked to the Warp to find a solution to his genetic sons' affliction. He found it, though the price of the bargain was high. Joining the Great Crusade with his Legion, Magnus and the Thousand Sons were determined to prove that the power of the Warp could be used as a potent tool in pursuit of human unity.
But across the galaxy, another of the Emperor's sons was afflicted by visions of salvation brought by a golden god and his one-eyed angel...
Grim Dark Lore 15: Bearer of the Word
Lorgar came to rest on the world of Colchis, a planet ruled by a theocracy known as the Covenant which believed in a pantheon of gods called the Old Faith. Tutored by his mentor Kor Phaeron, an exiled priest of the Old Faith, Lorgar was consistently troubled by visions of the coming of a golden, armored god and his one-eyed angel.
Lorgar grew to become a charismatic religious leader who led a civil war on Colchis to take over the Covenant and replace its faith with that of belief in Lorgar’s golden-armored savior.
After the arrival of the Emperor of Mankind and the Primarch Magnus the Red fulfilled his prophecy, Lorgar proudly took up the mantle of leadership of the Imperial Heralds Legion. He transformed them into the Word Bearers and proceeded to use the Great Crusade to spread worship of the Emperor as a god across the galaxy.
This directly contradicted the Imperial Truth and led to countless atrocities in the name of the Word Bearers' God-Emperor. As news reached the Emperor that His genetic son was spreading superstition and intolerance in his name, the Master of Mankind determined that Lorgar and the Word Bearers needed to be taught a hard lesson about the true nature of their mission...
Grim Dark Lore 16: The Perfect City
After taking command of the Word Bearers Legion, the Primarch Lorgar Aurelian had reshaped his warriors into a force dedicated to spreading his belief across the galaxy that the Emperor of Mankind was a god.
Horrified by this violation of the atheistic Imperial Truth, the Emperor brought Roboute Guilliman, the primarch of the Ultramarines Legion, to the city of Monarchia on the world of Khur. There the Master of Mankind harshly rebuked the Word Bearers for their failure by forcing them to watch as the Ultramarines destroyed the "perfect city" they had created in dedication to the divine Emperor.
In the wake of this event, Lorgar found his faith in the Emperor shattered but remained desperate to find some form of divinity to worship. His mentor Kor Phaeron and First Chaplain Erebus had long been secret devotees of the Chaos Gods and used this opportunity to push Lorgar to seek them out so he could learn the truth of Chaos' existence.
This quest led Lorgar on a pilgrimage into the depths of the Eye of Terror from which he emerged as the chosen instrument of Chaos Undivided. Determined to spread Chaos to Humanity to secure his species' future, Lorgar decided that only one man could truly serve the cause of the Dark Gods. And that was Horus Lupercal, his brother primarch, the best-loved son of the Emperor...
Grim Dark Lore 17: Triumph at Ullanor
At the great Imperial triumph held in that victory's aftermath, the Emperor announces his retreat back to Terra to pursue a secret project and the establishment of the new governing Council of Terra. Horus is made the Imperial Warmaster and supreme commander of the Imperium's military forces -- including his brother primarchs.
These actions set off tremendous acrimony among the primarchs. Many did not believe Horus should have been chosen to serve in that role and others were angered that mortals rather than primarchs would direct the future governance of the Imperium.
But for Lorgar Aurelian, this discord provided the perfect opening to put into motion the plans of the Chaos Gods that had been developing for almost 40 years. And the target of the Dark Gods' plot would be the new Imperial Warmaster himself...
Grim Dark Lore 18: Return to Terra
The Primarch Rogal Dorn of the Imperial Fists Legion joins the Great Crusade and becomes one of the staunchest servants of the Emperor. He is ordered to return to Terra with the Emperor so that the Master of Mankind can begin His great work.
Rogal Dorn was already an emperor in his own right when he met the Emperor of Mankind, having become the lord of the stellar empire created by the people of the frozen world of Inwit. Presenting the Emperor with the great star fortress Phalanx, command of the great starship was returned to him alongside mastery of the Imperial Fists Legion.
A master of the strategic defence, Dorn would become one of the Emperor's most trusted servants, nearly as beloved of his father as Horus. He was ordered to return from the Great Crusade to Terra to take over the defences of the Imperial Palace.
After the Ullanor Crusade, the Emperor returned to Terra to begin the next phase of His plan to restore Humanity's lost golden age. Among the initiatives He undertook were the creation of a new ruling bureaucracy for the Imperium, the Council of Terra, and the construction of new technologies in the Imperial Dungeons beneath the Imperial Palace.
But only a short time later, the Emperor was called away to deal with the momentous question of what place psykers should have in the Space Marine Legions and the Imperium itself...
Grim Dark Lore 19: Council of Nikaea
Facing increasing strife among His primarchs, the Emperor was forced to call a full meeting of the Imperial War Council on the specially terraformed world of Nikaea to deal with the issue of psykers in the Space Marine Legions and the wider Imperium.
But Magnus the Red, the primarch of the Thousand Sons, argued vehemently that no knowledge as inherently evil, and that true Human enlightenment could only be achieved through the use of the powers offered by harnessing the Immaterium.
Despite a last minute compromise offered by a band of Space Marine Librarians, the Emperor takes a hard line, and bans the use of psychic abilities among the Space Marine Legions. He orders the Space Marine Legions to disband their Librarius departments and remand their Librarians back to the battleline.
But Magnus the Red, incensed at the outcome on Nikaea, remained determined to show his father that the power of the Warp could still be used to further the goals of the Great Crusade...
Grim Dark Lore 20: Serpent in the Garden
Lorgar Aurelian and his servant First Chaplain Erebus of the Word Bearers Legion lay the groundwork of their grand conspiracy to turn the Warmaster Horus and half of the Space Marine Legions to the service of Chaos.
Lorgar Aurelian moved over the four decades after swearing his allegiance to Chaos to bring his fellow Space Marines into the service of the Dark Gods. He knew that their chosen instrument of enlightenment for humanity must be the Warmaster Horus.
The Word Bearers had found the means of that corruption on the Feral World of Davin, a world deep in the grip of Chaos whose primitive warriors were organized into lodges. From there Lorgar worked to spread the use of similar warrior lodges through all of the Space Marine Legions to serve as the vector of Chaos corruption.
And the opportunity to set the conspiracy into motion came during the XVI Legion's first contact with a people called the Interex. Erebus stole a Chaos artefact called the Anathame, which initiated an unexpected war between the Imperium and the Interex and laid the foundation of Horus' fall to darkness...
Grim Dark Lore 21: Horus Falling
Injured in battle with former Planetary Governor Eugen Temba on Davin's plague moon, the Warmaster Horus is taken to the Temple of the Serpent Lodge to heal, where he is corrupted into the service of Chaos.
The Warmaster Horus returned to Davin's moon to put down the rebellion of Eugen Temba, the Davin planetary governor who was a former friend of the Warmaster who was corrupted by Chaos. Temba had rebelled against the Imperium, and so First Chaplain Erebus manipulated the Sons of Horus and their commander into battle against the undead hordes of Nurgle.
Horus penetrated Temba's grounded flagship and faced his former friend, who had become a bloated monstrosity in service to the Plague God Nurgle. Though Horus defeated the former governor in battle, he was mortally wounded by the Chaos artefact called the Anathame that had been secretly given to Temba by Erebus.
Fearing for the life of their beloved Warmaster, the Sons of Horus in desperation turned their primarch over to the Chaos priests of the Temple of the Serpent Lodge for healing. His spirit cast into the Warp by a foul ritual conducted at the behest of Erebus, the Word Bearers first chaplain sought to corrupt Horus to the service of the Dark Gods of Chaos by playing on his insecurities and his desire for power.
Erebus' deception is unmasked by Horus' brother Primarch Magnus the Red, but the Warmaster trusts neither of his companions. Ultimately, the Chaos Gods make an offer that Horus, blinded by jealousy, pride and the constant need for adulation, just can't refuse...
Grim Dark Lore 22: Traitors
The Warmaster Horus uses a combination of charisma and psychological manipulation to bring the Primarchs of the World Eaters, Emperor's Children and Death Guard Legions over to his cause to rebel against the Emperor.
Needing allies to carry out his rebellion, Horus chose three other Primarchs as likely targets who could be persuaded to join the Traitor cause.
Angron of the World Eaters had always held a grudge against the Emperor since he had been rescued from his homeworld of Nuceria. Angron had been raised as a slave gladiator who fought for the entertainment of the masses of the city of Desh'ea. He led a slave uprising against the masters of Desh'ea that was ultimately crushed by the masters' armies.
The Emperor "rescued" Angron against his will by teleporting him up to an orbiting starship just before the final battle. He watched his adopted brothers and sisters slaughtered by the masters' armies and never forgave the Emperor this slight.
Fulgrim of the Emperor's Children had long been haunted by an obsessive need for perfection driven by his fear that his own imperfection had nearly wiped out his Legion soon after its birth due to an infection of its gene-seed.
This left him open to corruption by Slaanesh which was facilitated after Fulgrim came into the possession of a Chaos relic, a sentient silver daemonsword, on the world of Laeran. Manipulated by the daemon within the blade, Fulgrim agreed all too easily to Horus' tale that the Emperor had betrayed His sons and sought to become a god.
Mortarion of the Death Guard proved the most difficult to turn. But his hatred of sorcery due to his own experiences on his homeworld of Barbarus proved the key, as Horus convinced him that the Emperor was no different from the Chaos sorcerer who had raised and abused him in his youth.
That Mortarion also held a grudge against the Emperor for killing his adopted father when he could not made the betrayal all the easier.
Finally, Horus was informed that Magnus and the Thousand Sons had long been walking the path of corruption and would have little choice but to join the Traitors if he sent a specific message to Leman Russ of the Space Wolves at the right time.
Grim Dark Lore 23: Folly of Magnus
The Thousand Sons Primarch Magnus the Red discovers Horus' betrayal of the Emperor and attempts to warn his father of the civil war to come. This results in disaster for the Emperor's greatest project.
Magus the Red violated the edicts of the Council of Nikaea and used the power of psychic sorcery to contact the Emperor who toiled in the dungeons of the Imperial Palace. Aided from an unknown and unexpected source, most likely the Chaos God Tzeentch, Magnus managed to puncture the wards the Emperor had placed around the Imperial Palace to protect his Imperial Webway Project.
The Emperor's greatest secret was to connect all the worlds of Humanity to the Aeldari Webway so that Mankind would no longer need to rely upon the Immaterium to hold its interstellar civilization together. This would also starve the Chaos Gods of the psychic energies that made them a constant threat to all life.
But Magnus' sending inadvertently ripped a hole through the psychic wards the Emperor had erected to protect the Human extension into the Webway from assault by daemons. The Master of Mankind became a prisoner on the artefact known as the Golden Throne, a potent psychic amplifier He had used to create the Imperial extension into the Webway.
If the Emperor released His grip even for a moment, Terra would fall to a massive invasion from the Warp. And so a great war began in the Webway between the forces of Chaos and the Emperor's servants among the Legio Custodes and the Sisters of Silence.
Enraged at Magnus' violation of his oath, and unaware of the content of Magnus' message, the Emperor ordered Leman Russ and the Space Wolves to travel to Prospero and bring Magnus back to Terra for punishment. But Horus intervened and manipulated Russ so that he would seek to become Magnus' executioner rather than his jailer.
Grim Dark Lore 24: Dark Gambits
Horus prepares for his rebellion by manipulating his brother Primarchs into conflicts where they will be bogged down to protect his supply lines and open the way for his direct assault on the Throneworld of Terra.
Even after gaining the allegiance of three other Space Marine Legions as well as his own, the Warmaster Horus knew that many of his fellow Primarchs would never join his rebellion against the Emperor. So before he made his betrayal public he moved to bog down those Primarchs and Space Marine Legions he knew would stand against him in intractable conflicts.
Horus ordered the Word Bearers to launch a surprise assault against the Ultramarines of Roboute Guilliman who had mustered on the world of Calth under false pretenses. The result was the terrible Battle of Calth, which succeeded in dramatically reducing the strength of the largest of the legions and unleashing the Warp Storm known as the Ruinstorm to further isolate whole swathes of the galaxy from Terra.
Lion El'Jonson and his Dark Angels were ordered to undertake a long and difficult campaign against the Gordian League. After the Lion became aware of Horus' rebellion his Legion was assaulted by the Night Lords during the conflict remembered as the Thramas Crusade.
Sanguinius and his Blood Angels were sent into a trap prepared for them in the Signus Cluster. Determined to face the alien Nephilim, in fact the system had been consumed by Daemons in the hope of using the Blood Angels' secret genetic flaw to turn them to the service of the Blood God Khorne.
Finally, Horus intervened in the Emperor's attempt to bring Magnus the Red to justice for his violation of the Edicts of Nikaea, unleashing the terrible bloodletting forever remembered as the Burning of Prospero.
Grim Dark Lore 25: Heresy
Horus unleashes the first act of his rebellion on the world of ]]Isstvan III\\ by killing all of the Loyalists in his own Sons of Horus, World Eaters, Emperor's Children and Death Guard Legions so they will not oppose his treachery.
Having gathered four of the Legions whose primarchs had secretly sworn themselves to his rebellion in the Isstvan System to put down an uprising by Isstvan III's Imperial Governor Vardus Praal, Horus dispatched to the Isstvan III's capital of Choral City all the members of the four gathered Legions who had been identified as unlikely to betray the Emperor.
After they completed a successful operation destroying the rebellion of Praal and his Slaanesh-worshiping troops, Horus unleashed a planetary bombardment on his own warriors using virus bombs filled with the flesh-destroying Life Eater virus. But thanks to the heroic efforts of a few Loyalists, most of the betrayed Space Marines survived the bombardment, forcing Horus to engage in a months-long planetary assault to bring them to heel.
This bought time for the frigate Eisenstein and its Loyalist crew commanded by Battle-Captain Nathaniel Garro of the Death Guard to escape from the system and carry a warning about Horus' betrayal to Terra.
When the fires of Isstvan III had at last died down and the Loyalists in his own Legions had been dealt with, Horus prepared for the next part of his plan. He intended to lure several Loyalist Space Marine Legions to the neighboring world of Isstvan V...
Grim Dark Lore 26: Flight of the Eisenstein
Loyalists under the command of Battle-Captain Nathaniel Garro flee in the Death Guard frigate Eisenstein from the Isstvan III Atrocity to bring word of Horus' betrayal to Terra, which prepares to meet the Traitors on the world of Isstvan V.
In the wake of the slaughter of the Loyalist Space Marines of the first four Traitor Legions on Isstvan III, a group of Loyalists from the Warmaster Horus' flagship Vengeful Spirit managed to reach the Death Guard frigate Eisenstein under the command of Battle-Captain Nathaniel Garro.
Garro made the decision to believe the dissenters' tale of betrayal and then faced treachery from within his own ranks that convinced him to undertake an enormously fraught blind jump into the Warp to escape Isstvan III while being pursued by the Traitors within his own Legion.
Through a number of trials and tribulations, the Eisenstein's crew eventually managed to reach Terra and make their report of the Warmaster's treachery to the Primarch Rogal Dorn and Malcador the Sigillite, the Regent of Terra.
Taking their concerns to the Emperor, Dorn was placed in charge of assembling a massive response of seven Space Marine Legions to put down Horus' newborn rebellion on the world of Isstvan V. But the Sigillite was worried that perhaps the Loyalists were walking into a trap...
Grim Dark Lore 27: Massacre
Three of the Loyalist Legions, Ferrus Manus' Iron Hands, Vulkan's Salamanders and Corvus Corax's Raven Guard, are shattered at the Drop Site Massacre on Isstvan V when they are betrayed by four other Space Marine Legions that had secretly joined the Traitors' cause.
After the destruction of the Loyalists in the four original Traitor Legions (Sons of Horus, Death Guard, World Eaters and Emperor's Children) on Isstvan III, Horus established a new base on the neighboring world of Isstvan V. It was there that Ferrus Manus of the Iron Hands led two other Loyalist Legions, the Salamanders and Raven Guard, in the first wave of an assault seeking to put down Horus' rebellion once and for all.
But Horus' treachery ran deeper than anyone expected, as the four Legions of the second wave had already been turned to his cause, with disastrous results for the Loyalists. Ferrus Manus in particular would pay a high price when he at last confronted his once beloved brother Fulgrim for the final time...
Grim Dark Lore 28: Requiem for a Dream
Grim Dark Lore 29: The Siege
At last, the forces of the Warmaster Horus launch their great Siege of Terra, determined to draw the Emperor out of the Imperial Palace so that Horus can defeat him and take his place on the throne of the Imperium of Man.
The Loyalists, including the Imperial Fists, the Blood Angels and the White Scars, man the defences of the Imperial Palace erected and overseen by Rogal Dorn of the Imperial Fists. Their only chance is to delay the assault of the Traitors long enough for the Loyalist Legions of the Ultramarines, the Dark Angels and the Space Wolves to reach Terra and turn Horus' rapid assault into a war of attrition that he cannot win.
But despite all the efforts of his primarch sons, the Emperor knows that His time has come to face His wayward son once and for all. But to do so, he will ask Malcador the Sigillite to make the ultimate sacrifice...
Grim Dark Lore 30: Imperium Invictus
Pushed into a rash action by approaching Loyalist reinforcements, the Warmaster Horus invites the Emperor of Mankind to launch a personal assault on his flagship the Vengeful Spirit, where father and son meet in their final confrontation.
Despite Horus' attempt to seize the Imperial Palace rapidly and force the Emperor of Mankind to leave the Golden Throne and face him in a final battle to the death, Horus eventually just ran out of time. Informed that multiple Loyalist Space Marine Legion fleets were only hours away from entering the Sol System and transforming the Siege of Terra into an unwinnable war of attrition, the Warmaster made an impulsive decision.
Horus ordered his crew to drop the protective void shields surrounding the Vengeful Spirit, which would allow the Emperor and the Loyalists who accompanied Him to teleport up to the Chaos flagship. The Emperor took this as His cue, and launched an assault on the interior of the great ship aided by Sanguinius, Rogal Dorn, elements of their Legions and his ever-loyal Legio Custodes.
The result was the final conflict of the Horus Heresy as the Master of Mankind faced the Archtraitor in single combat. Only one would emerge alive -- and the fate of the galaxy would be changed forever...
Grim Dark Lore 31: The Age of Rebirth
With the end of the Horus Heresy, Roboute Guilliman takes command of the Imperium as its new Lord Commander and reshapes its institutions with an eye on preventing any further opportunities for civil war.
The Second Founding of the Space Marines is decreed, splitting all of the remaining nine Loyalist Legions into many different Chapters, while the Imperial Army is divided up between the Astra Militarum and the Imperial Navy.
The Astra Militarum is reshaped to serve as the Imperium’s primary military force while the Space Marines take on the role of planetary assault. Guilliman's Codex Astartes becomes the cornerstone of the culture and military tactics of the newborn Adeptus Astartes.
Guilliman establishes the Senatorum Imperialis at the Imperium's head, while new institutions such as the Inquisition and the Grey Knights become the Imperium's most potent and most secret weapons against the forces of Chaos.
The era ends with the disappearance or death of most of the remaining Loyalist primarchs and the near-mortal wounding of Guilliman by the Daemon Primarch Fulgrim of the Emperor's Children at the Battle of Thessala. For the next 10,000 years, Humanity would truly face the darkness of the galaxy without the aid of any of its legendary heroes...
Grim Dark Lore 32: Rise of Abaddon
The death of Horus at the Siege of Terra destroyed the unity of the Traitor Legions. Driven into the Eye of Terror by the Imperium during the campaigns of the Great Scouring, the Sons of Horus Legion soon found itself heading toward extinction without the unity brought by its lost leader.
But those who sought to save the XVI Legion knew that one man could save them -- Ezekyle Abaddon, the first captain of the Legion and Horus' rightful successor.
Driven into action by the theft of Horus' corpse by Fabius Bile and the Emperor's Children during the Legion War within the Eye, Abaddon was convinced by his brethren to take over leadership of the Sons of Horus, which he renamed the Black Legion.
After punishing the Emperor's Children for their affront, Abaddon launched a major incursion into Imperial space remembered as the 1st Black Crusade. During this campaign, he claimed the Daemon Sword Drach'nyen and the mantle of the new Warmaster of Chaos.
Grim Dark Lore 33: Saints and Beasts
In the wake of the 1st Black Crusade, the Imperium found itself enjoying a rare period of peace and prosperity. The growth of belief in the divinity of the Emperor of Mankind became explosive at this time, as the horrors of the Horus Heresy led many to seek comfort and reassurance in the growing cult of Emperor worship.
So rapidly did faith in the Emperor grow through the cult known as the Temple of the Saviour Emperor that by the mid-32nd Millennium it was recognized by the ruling Senatorum Imperialis as the state church of the Imperium and an arm of the Imperial government called the Adeptus Ministorum.
But this brief era of peace is brought to an end by the War of the Beast, a terrible conflict against the Orks that nearly sees the Imperium destroyed. In response to its hard-won victory over the greenskins, the Imperium establishes several new institutions, including the Ordo Malleus and Ordo Xenos of the Inquisition and the Space Marines of the Deathwatch.
Grim Dark Lore 34: Interregnum
The Imperium faces increasing strife between the growing political dominance of its state church, the Adeptus Ministorum, and the other organs of Imperial power even as the Imperium tears itself in half for over 800 standard years during the Nova Terra Interregnum.
In the wake of the War of the Beast, the new peace is soon challenged by the growing political strife on the Senatorum Imperialis between the Ecclesiarchy, the state church, and the other, more secular organisations of the Imperium such as the Adeptus Astartes and the Adeptus Mechanicus.
This conflict culminates in the Nova Terra Interregnum in the 35th Millennium when the entire Segmentum Pacificus, ruled from the world of Nova Terra, essentially secedes from the wider Imperium as a protest against the growing political dominance of the state church.
However, this schism was also propagated by the agents of Chaos, particularly the Renegade Dark Angels known as the Fallen. Additionally, the Mechanicus is also torn apart by religious dissension in the related Moirae Schism.
The Dark Angels take the lead in dealing with their Fallen brethren while the Mechanicus deals with its rebels internally. The result is the end of the Interregnum and the reunification of the Imperium at the end of the 35th Millennium. But a dark new era, an Age of Apostasy, now looms on the horizon...
Grim Dark Lore 35: Age of Apostasy
The growing conflict between the Administratum and the Ecclesiarchy ultimately results in the era known as the Age of Apostasy when the tyrant Goge Vandire gains control of both the Imperial state church and the Administratum. His eventual overthrow also leads to the birth of the Adepta Sororitas and the Ordo Hereticus.
Goge Vandire, the Master of the Administratum, launches a coup d'etat against his hand-picked ecclesiarch to also seize control of the Adeptus Minsitorum. With both state church and Imperial bureaucracy under his control he soon becomes the most powerful man in the Imperium. He proceeds to unleash a period of tyrannical terror remembered in later ages as the Reign of Blood.
Among the servants he gains during his tenure is a religious order of women-warriors known as the Daughters of the Emperor. Though his tyranny ultimately incites a revolt led by the reforming priest Sebastian Thor and his Confederation of Light, Vandire is ultimately brought down from within.
Seeking to end his tyranny, the Adeptus Custodes brings one of the leaders of the Daughters of the Emperor, Alicia Dominica, before the Golden Throne itself. After her meeting with the Emperor of Mankind, she returns to Vandire and executes him herself.
In the wake of the Reign of Blood, the Inqusition establishes the Ordo Hereticus and to protect the Imperium from its enemies within and the Ecclesiarchy creates the Adepta Sororitas, the Sisters of Battle, from the Daughters of the Emperor to serve as its new military arm.
Grim Dark Lore 36: The Great Devourer
A horrific new threat to the Imperium is discovered on the world of Ghosar Quintus in the form of the Genestealers and the Tyranid hive fleets whose arrival they herald. At the same time, an ancient alien species, the Necrons, begins to awaken at the behest of its long-missing ruler, the Silent King Szarekh.
In the last years of the 41st Millennium two new xenos threats to the Imperium were discovered. On the mining world of Ghosar Quintus, a Deathwatch Kill-team led by the Ultramarines Chaplain Ortan Cassius confronted the existence of the first Genestealer Cult.
At the same time, the Inquisitor Fidus Kryptman learned on the world of Tyran that a horrific alien species, the Tyranids of Hive Fleet Behemoth, had arrived in the Milky Way Galaxy from extragalactic space.
And in the deep void, the Silent King of the Necrons, Szarekh, moved to return to his slumbering people's Tomb Worlds and begin the Great Awakening to meet the coming threat of the Great Devourer.
Grim Dark Lore 37: The Time of Ending
As the era known as the Time of Ending begins, the Imperium confronts two new alien threats, the growing T'au Empire in the Eastern Fringe and the assault of Hive Fleet Behemoth in the Battle of Macragge.
A new alien threat arose in the late 41st Millennium in the Eastern Fringe of the galaxy – the T'au Empire. The T'au were a highly advanced if young humanoid species whose society was divided into four functional castes led by a fifth, ruling caste known as the Ethereals. The T'au subscribed to a philosophy called the Greater Good and created a multispecies empire which included some former Imperial worlds which chose to betray Imperial doctrine and join with the xenos.
Led by the Ultramarines Chapter Master Marneus Calgar, the Ultramarines and the Imperial Navy defeated the Behemoth at their homeworld in the Battle of Macragge. But the price proved incredibly high...
Grim Dark Lore 38: The 13th Black Crusade
Ezekyle Abaddon, determined to win the victory against the Imperium of Man that eluded Horus brought 10,000 years of planning and conflict to its climax when his forces emerged out of the Eye of Terror to conquer the world of Cadia.
Though the defenders offered up a valiant effort led by the new Lord Castellan Ursarkar E. Creed, the forces of Chaos proved overwhelming. With aid from the Necron Overlord Trazyn the Infinite and the Living Saint Celestine the Imperial defenders managed to keep Cadia standing despite an overwhelming Chaos assault.
Grim Dark Lore 39: Resurrection
Despite the best efforts of the Imperium of Man, Cadia falls to the 13th Black Crusade of Abaddon the Despoiler, but not before the survivors escape to the Ultramarines homeworld of Macragge and resurrect the Primarch Roboute Guilliman with the aid of the Aeldari Ynnari.
After a direct ground assault by Abaddon comes up short, the Despoiler grows tired of his sport and rams the remains of the Blackstone Fortress Will of Eternity into the Fortress World of Cadia, casting it into the Warp and destroying it.
Despite the loss of the Fortress World, Cadia's survivors led by Belisarius Cawl, Katarinya Greyfax and Saint Celestine forge an uneasy alliance with the Aeldari Ynnari and make their way to Macragge through the Webway on the moon of Klaisus. There they succeed in resurrecting Roboute Guilliman from his ten-thousand-year stasis so that he can face down the Black Legion.
Grim Dark Lore 40: Indomitus
After his resurrection, Roboute Guilliman undertakes the Terran Crusade to return to the Imperial Throneworld and meet with his father the Emperor, ultimately resulting in the birth of the Primaris Space Marines and the start of the Indomitus Crusade.
After clearing Macragge and Ultramar of the forces of the Black Legion, Roboute Guilliman led a great expedition of Imperial forces through the growing tumult in the Warp to Terra. Trapped by Kairos Fateweaver and the Red Corsairs in another Blackstone Fortress in the Maelstrom, the Imperials escaped into the Webway with the help of the Harlequins and the Fallen Angel Cypher.
After defeating Magnus the Red and his Thousand Sons following their arrival on Luna, Guilliman and his entourage headed to Terra where he met with the Emperor. After the meeting, Guilliman proclaimed himself the lord commander of the Imperium and the Imperial Regent.
With the aid of Belisarius Cawl he revealed the Primaris Space Marines and launched the Indomitus Crusade, determined to help the Imperium survive the opening of the Great Rift and the newborn Era Indomitus.