The Horus Heresy is the pivotal event in the 40K Universe. Its catastrophic events ended a potential golden age for Mankind, and instead plunged it into one of the most dystopic dystopias ever. The Heresy has been written and rewritten several times, including the current iteration from Games Workshops’ subsidiary The Black Library. Their version seems on track to be completed some time in the 2020s, so what follows pieces together the various versions which have been released up until now, with the current novels worked in. I’ve tried to make it both funny and informative. If people enjoy it, maybe I’ll do more of these. Hope you enjoy:
About 28,000 years from now, Earth as we know it is now known as Terra (which is Latin for Earth. Clever). And it is ruled by a being known only as Nathan Exp- I mean, the Emperor, or colloquially: Brutal Space Jesus.
It is largely implied that the Emperor had existed for thousands of years, pulling strings from behind the scenes to push Humanity forward through a few different golden and dark ages. Apparently, after it went tits-up the last time, he decided to take a more hands-on approach and take over. With more gothic architecture and Scandinavian heavy metal.
But even immortal Space Jesi want a family. So, through a combination of science and wacky space magic, the Emperor created twenty superhuman sons for himself, calling them Primarchs. Two of these were defective. Well, several of them were defective, but these two were especially defective, and had to be recalled and disposed of through ambiguous means. Plenty of theories exist about what happened to them and why, but none of them have any more credence than any other because Games Workshop has steadfastly refused to say anything about them other than once they existed, and due to some kind of undisclosed tragedy, they subsequently didn’t exist.
However, evil gods of Chaos scattered the primarchs across the galaxy while they were still babies, so the Emperor had to go with Plan B and using the genes of the lost Primarchs, created legions of somewhat less superhuman grandsons he named the Space Marines, and set out across the galaxy to find his lost kids. They smashed everything they found along the way that wasn’t human, and intimidated all the humans into joining his Imperium. The math for this is a bit sketchy. The Imperium supposedly has about a million worlds, and the Great Crusade, as it was called, lasted approximately two hundred years. 1,000,000/200 = 5000 worlds conquered per year. Pretty efficient, to say the least. Though it’s probably fair to guess that a good number of human settled worlds were like “You’ve got seven foot tall superhumans and the ability to destroy us from orbit? Uh… Praise this Emperor of yours” and complied peacefully.
Over time, he found all of his sons, and gave them command of the Space Marine Legion built from their genetic material.
One of the Primarchs was named Lorgar. All Lorgar ever wanted was to be loved by his Daddy. So much so that he built churches on every world he conquered (one million divided by- nevermind). This made Lorgar’s legion, The Word Bearers, conquer worlds significantly more slowly, but also, the Emperor was an atheist, and that pissed him off. So the Emperor had one of his favorite sons, named Guilliman, break Lorgar’s favorite toy, which Guilliman did because Guilliman was the good son who always did what he was supposed to. And was probably student class president, on the debate team, and the football team’s captain, which meant Lorgar was very envious of him.
Because all Lorgar wanted was validation, and he didn’t get it from the Emperor, he went looking elsewhere. Cue the return of the Chaos Gods, who wanted a more tangible and permanent way to mess things up in the universe but didn’t have enough power to do so yet. Lorgar met a daemon named the Fateweaver, who admitted to his face that it would tell one lie and one truth, so naturally Lorgar took everything it said at face value. After their little talk, Lorgar went back to work for his dad, conquering planets the right way this time, and pretending everything was normal.
At some point, the Emperor got bored of conquering the galaxy and went back to Terra to perfect a better way to get around the galaxy he called the Webway. The Webway had originally been built by ancient Space Elves, before the Space Elves had had a massive orgy that broke the universe and woke up one of the Chaos Gods named Slaanesh. In his stead, the Emperor picked another one of his favorite sons, Horus, to be Warmaster and lead the armies of Humanity. Horus was a lot like Guilliman, but he apparently told better jokes and threw cooler parties, so he was more popular with his brothers. And for a while, everything went okay.
It’s important to understand a bit more about the Primarchs at this point. They’re fairly flat characters, but they come from a time when their only purpose in the game setting was to be ancient heroes and villains from the long-long ago. So being a bit two dimensional wasn’t a problem. But, they all represented either elements from the classic Eight Evil Thoughts (Seven Deadly Sins), or the classic Roman Virtues. Which ones each individually represented would be important later, when factoring in who would go rogue and who would remain loyal, and a handful of degrees in between.
Lorgar and the Chaos Gods plotted for a while. Because Lorgar was perceived by his brothers to be weak and a follower, he was looked at more like a little brother and non-threatening. This allowed him to insinuate himself with Horus more closely. Horus was more or less the embodiment of Hubris and Avarice. Whereas Guilliman wanted to do great things and be the best because that’s what he thought the Emperor wanted, Horus wanted to do great things and be the best… so that he could be the best and be admired. Eventually, Horus was felled on a planet by a daemonic weapon, which sent him into a coma. While in the coma, one of Lorgar’s priests assumed the form of one of Horus’s favorite Space Marine generals and preyed upon Horus’s doubts and insecurities, convincing him that the Emperor had abandoned the Great Crusade and was planning to get rid of all the Space Marines as soon as the galaxy had been conquered. There’s no evidence either way in the setting what the Emperor’s true intentions were, but this becomes Horus’s chief motivation/obsession at this point.
Horus began secretly gathering the brothers he thought he could turn against their Father. Most of them were disaffected for a variety of reasons, or they were simply arrogant and foolish. These are, of course, the Deadly Sins guys, and not the Classical Virtues guys. And they plotted to overthrow the Emperor.
But first, they needed to get rid of their own internal loyalists, so they sent all these loyal Space Marines to invade one planet called Istvaan III (or spelled Isstvan, depending). Nobody stopped to ask why it would take elements from four Legions to kill one planet (one million divided by two hun- nevermind). And when they got down there, they were murdered from orbit by Virus Bombs and stuff. A small group of loyal Space Marines escape on the frigate Eisenstein and went to warn the Emperor.
Horus took his four traitorous Legions and camped out on a different planet in that system and waited. Unsurprisingly, their treachery didn’t go over well, and the Imperium sent seven Legions to go put the kibosh on them. The self-appointed leader of the impromptu task force, a Primarch named Ferrus Manus (Iron Hands in Latin) of the Iron Hands Legion (yeah, it was the 80s, what do you want?) decided that waiting was for suckers, and he took the first three Legions balls out into the defensive positions of Horus and his traitors. It went well at first. The problem was, Horus had also corrupted the four other legions who were part of the second wave. The first three loyal legions to land were slaughtered between the two groups of traitors, and Ferrus Manus got his head chopped off. The other two loyal Primarchs disappeared during the battle and only a handful of the Space Marines escaped the planet alive.
Meanwhile, Horus sent half of Lorgar’s Word Bearers to attack Guilliman’s Legion, the Ultramarines (who wear blue, of course). Horus knew that Guilliman was the good son, and would never turn against the Emperor. The problem was, Guilliman was also really good at being a general, and his Legion was much bigger than any of the others. Horus needed a way to distract him, and some expendable troops to do it. So Horus used his status as the Warmaster to send Guilliman on a mission to wipe out an alien empire that was as far from Terra as possible. Guilliman assembled a large chunk of his Legion on a planet called Calth. Then Horus told Guilliman that he was sending Lorgar to help out because Lorgar’s Legion kinda sucked, and needed the practice. Lorgar was still angry at Guilliman because, well, Lorgar was a little emo, and not really prone to rational decision-making. Lorgar didn’t go to attack the Ultramarines personally because the Fateweaver told him it wouldn’t end well. Whether that was one of the truths or one of the lies, eh… Either way, Lorgar didn’t go, and it didn’t go well. Despite having the strategic advantages of complete surprise, and daemons, the Word Bearers who went to Calth were slaughtered except for a handful that escaped in their few spaceships that weren’t destroyed. However, the Word Bearers had managed to destroy the bulk of the Ultramarines’ space fleet and created a massive supernatural storm in space that disrupted travel, stranding the Ultramarines too far away from Terra to intervene.
Another really loyal son was Leman Russ, Primarch of the Space Wolves. Leman Russ was like the Emperor’s good dog. He would do anything the Emperor told him and wouldn’t ask any questions as to why. And occasionally do stuff he thought the Emperor wanted him to do, too. Cut him some slack, he’s only a dog. The Emperor’s least reliable son was Magnus, Primarch of the Thousand Sons. Unlike Russ, Magnus liked to ask questions and learn stuff. The problem was, he wanted to learn stuff the Emperor had told him specifically not to, like wacky space magic. Magnus learned about the betrayal at Istvaan and tried to go warn the Emperor by using his wacky space magic powers. In the process, Magnus accidentally broke the Emperor’s Webway, ruining his space maze and unleashing daemons. Which, as you can imagine, displeased the Emperor greatly. The Space Wolves were sent (by Horus in some versions, by the Emperor in others) to punish Magnus. If Horus planned it, it makes a bit more sense. The Space Wolves don’t thrive on subtlety, and they attacked Magnus’s planet in a frontal assault. The result was the Thousand Sons were mostly destroyed, and the Space Wolves were pretty badly depleted, making them less of a threat to Horus. Magnus saved the last of the Thousand Sons by teleporting them off the planet to another part of the galaxy known as the Eye of Terror. More on that later.
With the Ultramarines neutralized, the Space Wolves distracted/depleted, and three other Legions effectively destroyed, Horus attacked Terra. He had eight Legions, and only three could be mustered at Terra in time to defend it. Realistically, Horus probably had far less than eight full Legions considering how much fighting and internal purging they’d done, but still likely had a significant numerical advantage. Which is a good thing to have when you are attacking the most heavily fortified planet in the galaxy. Why was it so heavily fortified? Well, one of the Emperor’s sons, Rogal Dorn, had been withdrawn to Terra years earlier to build it into a giant fort. Nobody really knows why. Was the Emperor afraid of the Webway? Did he have foreknowledge of Horus’s betrayal and just didn’t do anything about it? Was Rogal Dorn just incompetent and this was a way to get him off the front lines but let him still think he was important? Again, theories abound.
Horus showed up and the traitors proceeded to bomb the heck out of Terra for fifty five days (one million divided by two hun- nevermind). The traitor legions, many of which were now thoroughly corrupted by daemons, went apeshit on the planet. One of which, the ironically named Emperor’s Children, going on a continent-wide rape-fest, disregarding any tactical or strategic objectives. This… err… chaos, was unsurprising, since Horus himself had lamented that his nine Traitor legions were not the best of the eighteen. Angron however, Primarch of the World Eaters, who had unironically turned into a Daemon Prince of the Chaos God of Being Really Angry, was all about that action, boss. Daemon Prince Angron attempted to smash his legion against the walls of the Imperial Palace until they broke, hoping it would happen before he ran out of Space Marines to smash with.
At this point, the versions vary. The one thing that is consistent is that Horus lowered his shields on his command ship, and the Emperor, along with Rogal Dorn and another primarch named Sanguinius (of the Blood Angels. Sanguine-ius, Blood, yeah. Should I mention he also has angel wings?), and some other loyal troops teleported up there. Some versions suggest it was an accident the Emperor took advantage of, some say that reinforcements for the Loyalists were close and Horus was desperate, some versions say Horus was baiting the Emperor out of his palace-fortress. Either way, they get up there, and Horus’s flagship is a mess of Chaos mutation and corruption and they are attacked immediately by daemons. The loyalists get split up in the… err… chaos, and eventually Sanguinius encounters Horus.
Sanguinius plays an important, and oft-misunderstood role in the story. He gets criticized a lot for being “perfect” and “not having any flaws”. The thing is, that’s his part in the story. In introductory writing classes, it gets repeated a lot that good characters have flaws. It’s partly true, and good advice for aspiring writers, but usually has more to do with protagonists so they will be able to complete a character arc: grow, overcome obstacles, and change. Sanguinius’s place in the story is to be the perfect warrior of Humanity who is murdered by his own brother who has fallen to the most vile of temptations. Contrast and all that. Think of Sanguinius like Brad Pitt. Some people are just funny, and smart, and talented, and good looking. And so maybe Brad Pitt wouldn’t make an interesting protagonist for a story. It doesn’t make him an unrealistic person.
Anyway, Horus kills Brad Pit-
I mean Sanguinius. The Emperor shows up shortly after, seeing his angelic son broken and dead, and realizes he can’t save Horus and it’s go time. They fight. Except Horus is mega-powered by Chaos. At the end, the Emperor has to expend almost all his power to destroy Horus utterly (blasting his soul to bits and everything). The Emperor is mortally wounded, and has to be interred in a special Life Support Coffin called The Golden Throne so he can power a giant Space Lighthouse (which is how spaceships still have to get around since Magnus borked the Webway). And he’s been there ever since.
The Traitor Legions, now leaderless, rereat from Terra, being followed by what’s left of the Loyalists. Fortunately there’s a bunch of Ultramarines still, and Guilliman’s giant logistical nework lets him make more at a faster rate than anybody else. Not to mention the Traitors have lost all their homeworlds and other infrastructure, and a massive chunk of their leadership and Marines in the meatgrinder at Terra. Unable to reinforce themselves or regroup, they get hounded all the way back to the Eye of Terror, a region of space that is heavily borked by Chaos. Remember the Space Elf orgy from earlier that woke up an ancient and evil god? Yeah, this one’s their fault too. But since the Traitors are already corrupted, they go in anyway and the Loyalists can’t follow. The Traitors spend the next ten thousand years fighting eachother, and occasionally fighting the Imperium, who station a giant pile of troops and spaceships outside the front door to the Eye of Terror to keep it closed. Most of the remaining Traitor Primarchs eventually go insane and turn into daemons; all of the Loyalist ones eventually die or go missing (or both).
With the Traitors having been (mostly) driven off, and the Emperor confined to the Golden Throne, Guilliman decides that his duty is to make sure something like the Heresy never happens again. So he publishes a big book of rules for how to Space Marine, and then divides the Legions into smaller units called Chapters. This is both good and bad. On the plus side, the Space Marines become much more reliable and of better quality. A little more than half the Space Marine Legions were corrupted and turned to Chaos. The failure rate for Space Marines after the Heresy is closer to 2%. The downside is that the smaller-sized Chapters are much less powerful than the Legions, and mankind never manages to reconquer all of the galaxy.