In the backstory of the Warhammer 40,000 universe is humanity's era of hope, only just starting to dawn after the long and terrible Dark Age before being brought to an end by the Horus Heresy, wherein fully half of the best warriors the human race had to offer turned to worshipping dark gods and nearly wiped out the other half. The God-Emperor was permanently injured in a lethal duel with their leader, Horus (his son, in a way), to the point that he is only kept alive by an extremely complex life support device.Long established in the background as being directly responsible for the shape the galaxy is in in the 41st millennium, it is the subject of the Horus Heresy series of novels and audio books, by various authors.While the concept of finally fleshing out a canon backstory for 40k originally excited many long-time fans, the series has been met with widely varied opinions from its fanbase. The series is however the Black Library's most popular, with new titles regularly appearing in the New York Times best seller list.The series consists of:
Tales of Heresy, a short story anthology set during the time period, edited by Nick Kyme and Lindsey Priestley
Fallen Angels by Mike Lee
A Thousand Sons by Graham McNeill
Nemesis by James Swallow.
The First Heretic by Aaron Dembski-Bowden
Prospero Burns by Dan Abnett
Age of Darkness, a second short story anthology, edited by Christian Dunn
Promethean Sun a novella by Nick Kyme (limited to 3000 copies)
Aurelian, a novella by Aaron Dembski-Bowden (limited to 6000 copies)
The Outcast Dead, by Graham McNeill
Deliverance Lost by Gav Thorpe
Know No Fear by Dan Abnett
The Primarchs, a collection of four novellas, edited by Christian Dunn
Fear To Tread by James Swallow
Shadows of Treachery, the third short story anthology, edited by Christian Dunn and Nick Kyme
Angel Exterminatus by Graham McNeill
Betrayer by Aaron Dembski-Bowden
Mark of Calth, the fourth short story anthology
Vulkan Lives by Nick Kyme
Scars by Chris Wraight
The Unremembered Empire by Dan Abnett
The Imperial Truth, a short story anthology exclusively available at Black Library events in 2013
Vengeful Spirit by Graham McNeill
Sedition's Gate, a second event-exclusive short story anthology, from 2014
The Damnation of Pythos by David Annandale
Upcoming titles are:
Death and Defiance (2014), the fifth short story anthology (not counting event-exclusives)
Legacies of Betrayal (2015), the sixth short story anthology
The Crimson King (2015) by Graham McNeill
Master of Mankind by Aaron Dembski-Bowden
The Dark King and The Lightning Tower, two short stories by Graham McNeill and Dan Abnett (September 2010)
Raven's Flight by Gav Thorpe (February 2010)
Garro: Oath of Moment by James Swallow (December 2010)
Garro: Legion of One by James Swallow (April, 2011)
Butcher's Nails by Aaron Dembski-Bowden (May 2012
Grey Angel by John French (August 2012)
Burden of Duty by James Swallow (October 2012)
Garro: Sword of Truth by James Swallow (November 2012)
Warmaster by John French (December 2012)
Strike and Fade by John French (December 2012)
Veritas Ferrum by David Annandale (December 2012)
The Sigillite by Chris Wraight (March 2013)
Censure by Nick Kyme (July 2013)
Thief of Revelations by Graham McNeill (November 2013)
Khârn: The Eightfold Path by Anthony Reynolds (December 2013)
Lucius: The Eternal Blademaster by Graham McNeill (December 2013)
Cypher: Guardian of Order by Gav Thorpe (December 2013)
Hunter's Moon by Guy Haley (2014)
Wolf's Claw by Chris Wraight (2014)
''Garro: Shield of Lies" by James Swallow (2015)
"Battle of the Fang" by Chris Wraight is technically not a part of the Horus Heresy series, but it is the culmination of "A Thousand Sons" and "Prospero Burns".
Angels of Darkness by Gav Thorpe was written a few years before the Horus Heresy books got started, but its B-plot revolves around Astelan, one of the "fallen" Dark Angels, and his recollections of the final schism of the Dark Angels. Astelan would later become one of the focus characters in Fallen Angels.
Titanicus by Dan Abnett, which wraps up some hanging plot threads from Mechanicum.
Macragge's Honour, A comic book by Dan Abnett and Niel Roberts, which follows the crew of the Ultramarines' flagship as they give chase to Kor Phaeron during the battle of Calth.
Provides Examples Of:
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Action Survivor - With all the citizens getting caught up in events, there are bound to be a few. One of the most notable is Euphrati Keeler, a photographer who survived two separate daemon attacks, and even looks to be shaping up even further to being the first Imperial Saint.
A Form You Are Comfortable With - The daemon in Prospero Burns says that its true form would drive Kasper Hawser mad, so it uses Horus, Amon of the Thousand Son, and Navid Murza's forms instead. Strangely, it had planned on killing Kasper anyway, but it wanted to give its favorite pawn a painless death.
After the End: The Warhammer 30k era is essentially humanity rebuilding itself after its first empire collapsed. Just in the backstory, Earth had been rendered all but utterly inhospitable to life due to centuries of nuclear/chemical/biological (with a little sorcerous) warfare during the isolation of the Age of Strife; if the Emperor hadn't shown up when he did, it most likely would have continued on and been left a burned-out lifeless rock (though he burned his share of places). Then we get into all the OTHER planets that went through cataclysmic eras during that time, never mind those that were completely obliterated on purpose.
A Good Way to Die - All Space Wolves want this and want to be remembered for it. It's not that they want to die, it's that they want to die fighting.
The daemon that possesses Kasper Howser basically tells him this about the Thousands Sons and the Space Wolves' conflict.
Averted, in a prime example of how Tzeentch's plans always "fail", yet end up benefiting his power-base anyway. It was supposed to be a Mutual Kill, yet he ended up recruiting the Thousand Sons (which it probably planned for also), and both Legions survived.
All of the Other Reindeer: Some Primarchs were this way before they were rediscovered by the Imperium, due to just how different they were from vanilla humans. Some of those who would turn traitor were still suffered from this because of how they were radically different to the ideal the Emperor had in mind for them, (e.g. the Night Haunter being a psychopathic terror tactician and Lorgar setting up churches to the Emperor).
Amazon Brigade: The Sisters of Silence, composed entirely of Blanks, are a prototypical form of the Sisters of Battle.
A Mech by Any Other Name - Dreadnoughts and Titans play a big role in the story. Martian Knights bridge the gap between the two.
A Million Is a Statistic - In Prospero Burns, the Space Wolves drop a Quietude graving dock onto the planet below. The Wolves' response: howl, shout, and shake their fists. The Imperial Army Leader's response: To chew out Leman Russ for destroying the electronic data and knowledge from the dock.
Anachronism Stew - Melee weapons are prevalent in the 40K universe, as backups and as preferred weapons by some forces. 30K is no different.
Astartes melee weapons include ye olde axes. The cover of Prospero Burns shows a Space Wolf with a freakin' wooden buckler.
The official explanation for this - you can decide if it is a hand-wave or not - is that in the 40k universe, unlike our own, the balance of warfare has swung back to favor armor over ranged weapons. So, while in the modern world armor has played second fiddle to range since the advent of the musket, in 40k armor is once again ascendant.
And I Must Scream - You can't help but feel a little sorry for Fulgrim. In the Reflection Crack'd Fulgrim turns the tables on the Daemon and regains his body, trapping the Daemon in the painting. By then he's become even worse than the Daemon.
In Prospero Burns, the Space Wolves drop a graving dock onto a planet, making a continent sized crater. Also, they later use plasma energy, las bombardments, kinetic munitions, gravity bombs, targeted missiles, magma bombs, and atomic bombs on Prospero. It is hinted at that the bombardment created NEW FAULT LINES!
During the Battle of Molech in Vengeful Spirit, orbital bombardment obliterates the upper half-kilometer of a mountain, annihilating the forces around it.
Played with a bit. Because most readers of the Horus Heresy books will already know what's going to happen and have an omniscient view of the storyline they will know that "I can't say" is the challenge/answer phrase for the secret Lodges. Every time it is used, it always refers to clandestine lodge business that is not for the ears of outsiders. In Legion, it is used in an odd context, as the Alpha Legion is not shown to have a lodge. Then in Nemesis Constantin Valdor utters, in a completely different but equally clandestine context, "I can't say", reinforcing the theme of shadow wars and intrigue occurring in the background.
Samus is watching. Samus is all around you. I am Samus.
In later stories the phrase "The Emperor Protects" takes on hidden meaning.
In A Thousand Sons and Prospero Burns we have "There are no wolves on Fenris."
"Let the galaxy burn." 10,000 years later, the Traitor Legions are still following Horus's orders.
"The Mark of Calth" is becoming one for the Ultramarines, essentially becoming their version of Never forget.
The Kinebrach Anathame is a magically-crafted weapon and the sword that wounded Horus and set him up for his fall to Chaos. It's not done doing horrible things yet.
The Laer Blade seemed to be a primitive sword, albeit perfectly made. Any reader who's familiar with it, will know that it was host to a Keeper of Secrets.
Artifact Title: While the Warhammer part of the title was already an artifact around the 2nd edition of the tabletop game, in the context of the Horus Heresy series, the 40,000 part of the title becomes one as well, as it takes place around 30,000 AD.
Artificial Limbs: In the thirtieth millenium, replacing weak or destroyed parts is a fairly common procedure, sometimes done voluntarily.
It is mentioned Bear will get one after Prospero Burns.
Throughout the series, Adeptus Mechanicus characters are shown wearing all sorts of extreme cyber-implants, as their faction sees this as a form of worship.
In the novella Feat of Iron from The Primarchs, the Iron Hands' predilection for artificial limbs becomes a key plot point when the Eldar use sorcery to control those limbs to attack their owners
Atop a Mountain of Corpses: The Blood Angels find the Cathedral of the Mark in Fear to Tread: A massive temple devoted to Slaanesh made entirely out of human bones.
Attempted Rape: Invoked Trope. In Fulgrim, Serena D'Angelus makes this excuse to Lucius, lying that she murdered a remembrancer in self-defense because he was about to rape her. To really hammer in how the legion is falling in on itself, Lucius shrugs it off, telling her that he would send somebody in to clean up for her.
Authority Equals Asskicking: More or less a requirement for being the First Captain of a Space Marine Legion. Ezekyle Abaddon of the Luna Wolves/Sons of Horus, Sigismund of the Imperial Fists, Raldoron of the Blood Angels, Sevatar of the Night Lords, Jubal Khan of the White Scars, and Gabriel Santar of the Iron Hands are all considered the best warriors of their respective Legions. Even the more intellectually inclined Legions First Captains, such as Ahzek Ahriman of the Thousand Sons and Ingo Pech of the Alpha Legion, are noted for being formidable warriors. Kor Phaeron, as First Captain of the Word Bearers defeated Roboute Guilliman in single combat, and could have killed him had he not decided to try his hand at corrupting him. He is arguably the single most formidable combatant in the Legions that is not a Primarch.
Space Wolves wear hand-made leather clothing. They also drape tan wolf hides over their armor.
Simple robes are a staple of Imperial clothing.
Awesomeby Analysis: The Ultramarines have this as their hat, in addition to ruthless efficiency and peerless discipline. Sergeant Thiel recognises that bladed weapons and flames work better against Daemons because of their ritual significance, and also works out the ingress points on his ship that the Word Bearers would use.
Axe Crazy: Angron has "butcher's nails" implants in his skull that drive him with constant pain and aggressive urges. This coupled with his perpetual anguish over how the Emperor basically made him watch his best friends die, makes him utterly incapable of relating to (relatively) normal human beings. This coupled again with how the Nails keep him from any restive sleep further contributes to his insanity, and the combined exhaustion is slowly killing him. Nevertheless, the World Eaters willingly take the same horrible implants (a much, much less severe version, of course) in order to gain an insight to their Primarch's character and to better relate to him. In essence, they seek kinship with their father by breaking themselves on the same anvil upon which he was shattered. It's quite beautiful, in a twisted way...
Angron has made several master-crafted axes that have become Legion heirlooms. One was gifted to Lorgar, but lost on the Furious Abyss. Another two, the twin axes Gorefather and Gorechild were used, until he lost Gorefather and "gave" Gorechild to Kharn.
Awful Truth: In The First Heretic, Lorgar and the Word Bearers discover the "Primordial Truth" of Chaos, where Ingethel says that those who accept the Chaos Gods will be taken into their power, while those who reject them will be cast out and eaten by daemons, and that the Emperor created the Imperial Truth to deny Chaos and damn humanity to stagnation. There's just one problem: Ingethel was lying.In Deliverance Lost when a Word Bearers ship is pulled into the Warp by the Raven Guard, the crew, both human and Word Bearer, are eaten by daemons. The Chaos Gods don't care what happens to those who worship them.
I am the Storm's Blade, I am Justice, I am Defiance and I am the Oath Keeper! -Cerberus, Legion Of One
Now? Now Prospero falls. -Leman Russ, Prospero Burns
I will find you, I will kill you, and hurl your toxic corpse into Hell's mouth. -Roboute Guilliman, to Lorgar
Badass Bookworm: Kasper Hawser is remade by the Space Wolves. They give him super strength, youth, fast reflexes, and an eye that uses night vision. Without any training in fighting, he takes out several Imperial Army personnel without breaking a sweat.
Dinas Chayne, an elite Lucifer Black but still an standard human, manages to fight the Primarch Alpharius for a few moments. Maybe. It might have been a regular Alpha Legionnaire.
A mild example would be that of the Priest in the short story "The Last Church". He openly defies the Emperor, willingly choosing death rather than to personally walk off with him. This is an old man, alone in the last Church on Terra. He is surrounded by proto-astartes. After the Emperor has spent the last hour trying to destroy his faith via argument, he defies the Emp to his face. It's hilariously ironic given it was the Emperor who unintentionally inspired him to turn to faith in the first place and therefore not even the being he thought was God, telling him not to believe could break his faith.
Galaxy In Flames is a Foregone Conclusion since it details the events that happened at the beginning of the Horus Heresy.
Fulgrim, since it details Fulgrim's descent to Chaos, and he manages to become the badguy who won. He's the only Primarch that's flat out won in his every appearance. While every other Primarch is off fighting his own petty battles, Fulgrim gets the first Primarch kill of the Heresy, fights off the deamon who possessed him, and has the first legion to successfully convert to recognizable Chaos Marines.
Batman Can Breathe in Space: In Know no Fear Roboute Guilliman gets knocked off his flagship's bridge into space and without a helmet by a daemon attack. It's in low enough orbit that there's a very thin atmosphere, which is enough for the primarch to survive for several hours and then still have enough stamina to punch some Word Bearers to death.
Batman Gambit: Erebus exploited Horus's pride to convince him to lead the forces to Davin's moon (Kyril Sindermann describes Erebus's performance as the greatest acting job he's ever witnessed) and then exploited the Mournival's devotion to Horus to let him take Horus to the Serpent Lodge.
Battle Cry: The Space Wolves makes snarls, roars, and "leopard-growls".
Battle in the Center of the Mind: An unusual case where Kasper Hawser's mind was being altered by a daemon. He couldn't fight the beast and he could only regain his memories by altering his dreams. Space Wolf Rune Priests attempted to help him fight the being, but one of them was turned into a wolf. This priest claimed Horus turned evil. Later on, Kasper walks through a room in Tizca and into the room that he is in in his dreams. The daemon combined the two realities. Therefore, it was a battle in the center of the mind outside of the body (where Space Wolves could run into his mind and shoot it). It took the arrival of a Rune Priest, two dreadnoughts, and two dozen Silent Sisters to beat it back.
In Fear to Tread the Blood Angels find ships that tried to flee from Signus Prime that lacked warp-engines, meaning that the people knew they were going to die in space. Being Astartes, they're mystified as to why anyone would do that, until the Shipmistress of the Red Tear explains it: whatever was happening in the Signus Cluster was so terrifying that they willingly chose death in the void over being killed by the invaders.
Blatant Lies: "There are no wolves on Fenris". Fenrisian wolves are actually normal humans who succumbed to the same genetic engineering flaw that creates Wolfen from Space Wolf Marines when the planet was being colonized. There are no wolves, just mutant humans.
Blind Seer: Cyrene Valantion, aka "The Blessed Lady", in The First Heretic
Eada Haelfwulf and Ulvurul Heoroth, AKA, Longfang in Prospero Burns. Also, Thousand Son Astartes and the daemon bleed from the mouth, well as other orifices, when confronted with powerful marks of aversion and pariahs.
Anyone dumb or desperate enough to use Enuncia.
Blood Magic: Aside from the obvious Chaos-related nastiness, the Black Cube that the Nurth possess requires the deaths of hundreds, even thousands, of people to activate.
Brown Note: The word of banishing that Navid Murza and later Kasper Hawser used in Prospero Burns causes gums to bleed and teeth to loosen.
Brutal Honesty: Captain Amit of the Blood Angels Fifth Company has need for tact. It serves him well, though; his bluntness makes him the only one of the Blood Angels willing to draw the (correct) conclusion that Horus has turned traitor.
Cain and Abel: Rather than a single case, it's essentially half a fraternity of Physical Gods becoming the Cain to the other half's Abel. There are also specific cases between individual Primarchs. Most notably, Perturabo is the Cain to Dorn's Abel; then there's Russ, the loyalist Cain to Magnus's Abel.
Call Back: Throughout the series. For example in The First Heretic, Argel Tal, during his trip in the Immaterium with Ingethel, gets to visit the labs of Terra as the Primarchs are being grown. Which appears to be the same scene Horus will be subjected to on Davin, forty years later, in False Gods.
Calling the Old Man Out: Horus does this to The Emperor and he decides to drag the rest of the galaxy into it for fun.
The Cavalry: At the end of Know No Fear when Captain Ventanus and the 4th Company are on the verge of being overwhelmed by Hol Beloth when reinforcements show up, and by reinforcements, we mean the 19th company under Captain Aethon, the remnants of the 111th and 112th companies under Sergeant Anchise, three Titans under Tetrach Tauro Nicodemus, and Army forces under Tetrach Eikos Lamiad. They are pissed.
Cassandra Truth: At least three separate attempts are made to warn others about Horus's impending fall to Chaos. Magnus's attempt gets the Space Wolves unleashed on Prospero, Eldrad's attempt gets the Maiden Worlds in the Perdus Anomaly virus-bombed, and Leman Russ treats Eada Haelfwulf's dying words as Magnus's attempt to fabricate corroborating evidence.
Child Soldiers: The Lucifer Blacks had served as soldiers since kids, which is why they're all badass and nearly all gone when the Imperium rediscovers their world and puts an end to the matter.
The Emperor is sometimes cited as having been destined to rule humanity in the meta sources.
Then there's Horus as the Chosen One of the powers of Chaos, reminding us that this trope isn't always a good thing.
Combat Pragmatist: Loken, when challenged to a sparring match by Lucius, starts and finishes it by grabbing his sword arm and punching him in the face. He warned Lucius that the match wouldn't just be about the sword.
Combined with Trigger Phrase in Prospero Burns. A daemon could hurt a person with magic if it knew the person's name. These names were stolen from Kasper Hawser's mind.
As part of John Grammaticus's repertoire as a "logokine", he manages several flavors of this in Legion.
Conflicting Loyalty: A few marines suffer from this: who first, their Primarch or the Imperium?
Continuity Nod: The authors seem to have a contest as to who can put more of these per-book than the others.
Prospero Burns: We meet a Space Wolf called Bear. His arm is destroyed by a daemon during the scouring of Prospero and replaced with an augmetic. Shortly thereafter we learn that his name is actually Bjorn, indicating that this is actually Bjorn the Fell-Handed, who would go on to become the most famous Dreadnought and the oldest loyal Space Marine in the 41st millennium. Though becoming a Dreadnought is considered an honor, Bjorn was happy when he only lost an arm instead of being forced to become a Dreadnought. Obviously, his luck didn't hold out.
In the Age of Darkness story "Rules of Engagement", an Ultramarine Captain thinks it will take something far greater than traitor assault to destroy the beauty of Prandium. Ironic when you consider it gets eaten by Tyranids.
In Nemesis Siress Callidus wants to deploy a new Callidus assassin to kill Horus. The assassin's name? M'shen, the woman who assassinated Konrad Curze.
Virtually all the major Iron Warriors players in Storm of Iron appear in Angel Exterminatus. Only Honsou is missing. The last line of the book is a namedrop to him.
McNeil does one against himself. A third of the way through The Outcast Dead we see The Emperor receive the ill-fated psychic warning from Magnus, which leads to the Space Wolves going to Prospero for some smashy-smashy. The book says this takes place after the events of Galaxy in Flames and that Terra is already aware of Horus' treachery. However, both False Gods and A Thousand Sons (both written by Mc Neil!) explicitly say this happened before the Istvaan III massacre.
The Flight of the Eisenstein states that Saul Tarvitz was the First Captain of the Emperor's Children and that Garro could see the oceans of Terra from space. Previous books had established that Tarvitz was never one of Fulgrim's chosen elite, and that those oceans had long since been boiled away in nuclear war. The oceans are back again in Prospero Burns. The idea seems to be be that small seas remain, which is shown in Nemesis.
Early books in the series show Sanguinius as "raven haired", when in Fear to Tread, he's suddenly the blonde that he's shown as literally everywhere else. This one is explained away in The Unremembered Empire. Much like the Emperor, some Primarchs, such as Sanguinius, are seen by others in the way that the viewer subconsciously finds most pleasing or suitable (or possibly in the way that the Primarch wants to be seen).
Kharn's appearance in Galaxy in Flames has him as his 40k self, a frothing, insane, madman, whilst the later novels about the World Eaters such as Betrayer don't have them falling to Khorne until after Angron ascends to daemonhood during his duel with Roboute Guilliman on Nuceria.Later 40k novels portray Kharn similar to his 30k self, making this more of a Characterization Marches On.
Vulkan Lives is internally consistent, but makes absolutely no sense in the face of established Salamanders lore, especially regarding the Tome of Fire. In short, if Vulkan Lives is to be considered the true story, literally everything we know about Forgefather Vulkan He'stan and the Tome of Fire is a lie.
Fulgrim has a taste for these. He originally wielded Fireblade, a sword made by Ferrus Manus. He later used the Silver Blade of the Laer, which he took as a trophy, but that ended poorly, and in the end wend to Lucius. And during the Heresy itself, he used the Athame, which was a gift from Horus. At one point, he briefly owned all three of those swords at one time.
For the more mundane types, Thiel's Electro-magnetic longsword. Capable of shearing Word Bearer in two, cutting through star ship hulls and killing daemons more effectively than any ranged weapon
Cosmic Horror Story: Well into the Heresy, some people within the Loyalist factions begin to suspect that Horus is being manipulated by something, and a much bigger story than the galaxy at civil war is playing out behind the scenes.
Averted in The Last Church. It's strongly implied that the priest is the last Christian on Terra, who manages to face down the Emperor in a battle of words.
Averted also with the Catheric faith, which some Terran veterans somehow still follow.
Cultured Warrior: The Emperor's Children take this to the point of arrogance. The Thousand Sons as well—preserving libraries and knowledge (particularly of sorcery, but all subjects are considered important) is a primary goal to the point it brings them into conflict with the Space Wolves, and individual members have hobbies like philosophy and winemaking. Horus and his Mournival also fit the bill pre-corruption.
Dark Messiah: Horus (thanks to Chaotic manipulation) thinks that he is saving the galaxy by causing this Hersey..
Deadpan Snarker: Many examples. Lorgar is an excellent one, showing this trope when he is very angry with Erebus after Kor Phaeron and Erebus badly screw-up the invasion of Calth, turning what should have been the death of the Ultramarines into a stalemate and Ultramarine strategic victory. Even Angron starts laughing.
During Horus' time in the Temple of the Serpent Lodge, he speaks to one of his senior captains who had died in the events leading up to Horus Rising. Subverted, because it was Erebus disguised with sorcery, although the readers know this by the time it occurs.
Kasper Hawser has a twelve minute conversation with Longfang, in his mind, after the latter's death.
Ut is especially prevalent in Know No Fear. As a result of the Campanile hitting the Calth Veridian Yard causes the Antrodamicus to crash into Kalkas Fortalice. Then it goes to its Logical Extreme when an orbital depot is destroyed and parked vehicles start falling out into atmosphere—and right above the Ultramarines 6th Company.
In Prospero Burns, Kasper Hawser's actions and memories are altered by a daemon. It is More Than Mind Control.
Spear, in Nemesis? Not sure as he's not so much possessed as he's wearing a daemon as his skin.
Depending on the Writer: Carefully averted. So far it has had seven different authors who meet at least once a year to coordinate stories and fuel each others' ideas. The results of this intense collaboration have been impressive, to say the least.
Perturabo (who is either a tortured would-be democratic intellectual, artist, engineer, and diplomat forced into dirty, mud-splattered trench-fighting by his disdainful family until he snaps, even then retaining more of his humanity than the other traitors, or a cold-hearted pragmatist who ordered a tenth of his legion killed moments after meeting them for no discernible reason before developing a "numbers-game" style of calculated attrition that earned his brothers' well-deserved scorn).
Disproportionate Retribution: The Emperor's rebuke of Lorgar proclaiming him as a God was the cause of his fall to Chaos, but The First Heretic shows just what that rebuke entailed: ordering the Ultramarines to destroy the city of Monarchia, which exemplified the Word Bearers accomplishments, then ordering Lorgar and the entire Word Bearers legion to kneel before the Emperor, Roboute Guilliman, and Malcador the Sigillite in the city's ruins as they re-pledged themselves to the Great Crusade. Even the other Primarchs thought it was excessive. Is it any wonder that the Word Bearers betrayed the Imperium?
Distant Finale: Know No Fear has one 25 years later (or over 219,000 hours on the Mark of Calth), after the end of the Heresy, with Captain Ventanus participating in the Exterminatus of Colchis during the Great Scouring.
Divided We Fall: The Imperium of Man is fighting itself. In this corner, The Emperor and loyalist Primarchs and in the other corner, Horus and the traitor Primarchs.
Doomed by Canon: Don't get attached to the loyalist characters. Don't get too attached to the traitors, either. Some of their fates are indeed worse than death. The survivors of the books tend to be condemned for their heresy to spend eternity as expensive pieces of plastic.
There are many occasions in the first few books when the characters consider scenarios like Astartes fighting Astartes or Horus trying to take a fortress defended by Rogal Dorn before dismissing them as impossible.
The end of Fallen Angels shows Lion innocently handing over the engines, which he defended from Horus, to Perturabo.
Nathaniel Garro would have died on Isstvan Extremis if Fabius Bile hadn't administered emergency medical treatment. Doubtless he would have ignored Garro (or put a surreptitious bolt in his head) had he any inkling of how much trouble he would be.
Dramatis Personae: Every book has one or two pages listing the main and peripheral characters. Thankfully, they don't spoil much.
Space Wolves have a tradition of honoring those who died by passing down oral stories of warriors' lives. Well respected warriors receive a big "sending" or feast, in which a skjald or a good storyteller recites all the deeds of the fallen warrior.
Dying as Yourself: Temba in False Gods manages to overcome Nurgle's influence before his death.
Earth Is the Center of the Universe: Politically, and perhaps culturally. Most maps of the Imperium (based on the borders of the Astronomicon) are centered on Terra (which has the Astronomicon on it).
Eating the Eye Candy: Mersadie Oliton takes a good long look at a nearly-nude Garviel Loken in Horus Rising.
The Emperor: Shows up all over the place, although any given appearance is typically very limited.
Even Evil Has Standards - The Traitor Legions may have broken their oaths to the Emperor, but they still have standards.
In Nemesis, Horus Lupercal forbids Erebus from employing any further assassins against the Emperor, as he considers assassins tools of cowards and the Heresy must end with Horus killing the Emperor.
When the Night Lords discover that the extent of the Word Bearers corruption goes to making several of their members hosts to daemons, they refuse to let the Word Bearers anywhere near them.
In Angel Exterminatus, when the Iron Warriors realize just how depraved and insane the Emperor's Children have become, they're not just unnerved, they're outright disgusted. Then they find out what Fabius Bile has been up to in his spare time. Even people who spent their last pre-Heresy engagement committing genocide on their home planet consider Bile's horrific surgeries on Space Marines to be over the line.
Surprisingly, the Emperor's Children still have some standards when Lucius tells them that Fulgrim has been possessed by a daemon, and they resolve to free their Primarch. Granted, it was partly because they wanted to enjoy the sensation of fighting a Primarch, but it's pretty clear that Lucius, Mairus Vairosean, Julius Kaeseron, and Fabius Bile are motivated out of genuine loyalty to Fulgrim.
An ambiguous case with Fulgrim himself because of the daemon possessing him. It's implied that he engaged in necrophilia with the corpse of a female remembrancer at the end of Fulgrim.
Evil Chancellor: Cypher may have been this for Luther. As with everything regarding Cypher, it's ambiguous.
Erebus and Kor Phaeron are Lorgar's closest and most trusted advisors. Kor Phaeron, his adopted father on Colchis, secretly kept the old religion alive and taught it to the Davinites while Lorgar was spreading the cult of the God-Emperor. That religion was an interpretation of the Chaos Gods. Erebus, also a follower of the Ruinous Powers, spread their knowledge and promises of power to the other legions through the warrior-lodge system and set the Heresy in motion.
During the Great Crusade, Horus and Sanguinius were closer than any other Primarch. Anyone familiar with 40K's backstory is well aware of how that turns out.
Fulgrim and Ferrus Manus are said to be two of the closest Primarchs - They forged each other's weapons and both sought perfection in their own way. When Ferrus refuses to turn traitor when Fulgrim reveals his treachery, it turns into a fight. When the Heresy begins, Ferrus becomes the first Primarch killed, and Fulgrim is holding the sword that did it.
Fake-Out Opening: The first line of the first book is, I was there, the day Horus slew the Emperor..
False Flag Operation: Lucius and Solomon Demeter kill a bunch of Emperor's Children on Isstvan III in Fulgrim. Lucius reveals that it was a feint and he got Demeter to kill his own men so Lucius could rejoin the legion.
Every primarch to their legion, both figuratively and literally, up until half of them go rogue, anyway. Then it gets a bit less pleasant.
Averted figuratively with Perturabo, as The Crimson Fist novella in Shadows of Treachery indicates that Perturabo was killing Iron Warriors who had failed him even before the Heresy began.
Even after the Heresy starts, Lorgar still valued the lives of his Word Bearers. He almost gets killed trying to save the Gal Vorbak from the Raven Guard.
The Federation: The Interex come off as this compared to the Imperium, which is already showing signs of being The Empire. They're a highly technologically advanced society similar to the Tau who cherish peace and are willing to extend the hand of friendship to aliens; not only is their society literally built on a centuries old alliance with a once-dying alien race called the Kinebrach, they defeated the disturbingly Tyranid-like Megarachnids and chose to simply strip them of space-faring capabilities and imprison them on an otherwise uninhabited world around which they posted warning beacons, as opposed to simply massacring them. One Interex character, when questioned about this, proclaims that they had no right to annihilate another species just because it was different. Furthermore, they are well aware of the dangers of Chaos and regard it rationally and openly as a threat that must be opposed by all sentient beings. In fact, they are hesitant to embrace the Imperium because they see its brutal, war-like ways and fear it is already tainted by Chaos. Naturally, they are plunged into war with the Imperium and utterly destroyed by it.
The Fettered: Because of the Edict of Nikaea, every loyalist Librarian (psychic Space Marine) is supposed to be this. Since some of Horus's worst weapons are psychic in nature, it's a nasty self-inflicted wound for the Imperium.
Fire-Forged Friends: The best way to get Astartes of different Legions to bond is to have them kill people together. Aww.
First Name Basis: The Astartes were friendly in Pre-Heresy times; some of them were, anyway.
Five Rounds Rapid: quoted as a Shout-Out in Fallen Angels, used in spirit in a number of other places, usually when a new Legion first faced Chaos-based nasties.
Flashback to Catchphrase: The series shows some of several iconic phrases of the 41st millennium being spoken for the first time:
In Galaxy in Flames, Horus orders the Vengeful Spirit to open fire on Isstvan III to start the firestorm phase of the virus bombing with the words that started the Horus Heresy, and which Abaddon would use to start the Black Crusades: "Let the galaxy burn!"
In The First Heretic First Captain Sevetar of the Night Lords become the first to utter the phrase "Death to the False Emperor!", a Battlecry that followers of Chaos have been using for ten thousand years.
Foregone Conclusion: Virtually every single major event in the entire series. We all know how Horus' Hersey is going to end. What makes it interesting is the few loyalists who remain in the Traitor legions, and the characterization of those characters who had previously been relatively one-dimensional villains.
Foreshadowing: Starts as early as the first chapter of Horus Rising, where a Terminator squad in the Luna Wolves is described as wearing black armor. Even more so because these particular Terminators are part of the First Company, commanded by none other than Abaddon. Yes. That Abaddon.
Four-Temperament Ensemble: The Mournival was designed with this idea to provide Horus with advice from a spectrum of temperaments.
Freudian Excuse: Ahriman was terrified of the legion being killed by mutations ever since his brother died from them.
Friendly Sniper: Tarkan and Pergellen, both Iron Hands, showing just how different things were before the Horus Heresy.
From Bad to Worse: A side-revelation in Mechanicum. Forget Chaos for a moment. Those puny bastards have only been around for a few tens of thousands of years. Sol, the heart of the Imperium and cradle of humanity, is home to the Void Dragon, a C'tan star god that could eat the Sun if it woke up on Mars. It gets worse- the Void Dragon is the Machine God that the Mechanicum, essentially humanity's technological backbone, unknowingly worships, and its primary aspect is complete control over technology. The God-Emperor who beat it up in the past is now on life support so even if he wasn't getting played all along by a nearly all-powerful, billions of years old God, he can't do a thing to stop it now. The method of keeping the Void Dragon sealed is probably lost forever because one of the party in Mechanicum stole the book needed to teach the Dragon's next keeper what he needs to know to do the job. Generally, people figure Zouche was the Deceiver in disguise. All of this is a back burner problem.
Genuine Human Hide: We are contractually obligated to remind you that Chief Apothecary Fabius of the Emperor's Children has in his possession a lab coat made of human skin. It makes its first appearance in The Reflection Crack'd, where it's revealed to be from the skin of loyalist Legionaries slain during the Drop Site Massacre.
God Emperor: Constantly talked about, rarely featured directly. When he makes an appearance, it's often a eerie yet awe inspiring experience for those involved.
The Good Chancellor: Malcador the Sigillite, mentioned in passing in game materials, finally appears here. The Emperor's right-hand man, he plots on a level that would make Lord Vetinari jealous, while holding everything together day-to-day.
Good Is Not Nice: Barthusa Narek. Word Bearer and loyal devotee of the God-Emperor. He still took part in the Drop Site Massacre at Istvaan V and only defected after seeing how far his Legion had fallen. Now his only goal is to kill Lorgar and save the soul of his once great Legion. However none of that makes him your friend if you are a loyalist. Get in his way and he will kill you as Vulkan found out in The Unremembered Empire.
In Horus Rising, Loken tells Karkasy to tell the truth, no matter how ugly and horrible it is. By False Gods, Karkasy is still telling the truth, as ugly and horrible as it is, by slandering the Imperium and supporting an outlawed cult. Horus has Karkasy killed for it.
In Fear to TreadThe Plan to turn the Blood Angels to the side of chaos by unleashing the Red Thirst in the middle of a battle with Chaos daemons ends with the Blood Angels unleashing a Curb-Stomp Battle on the daemons and giving Sanguinius time to recover from a Mind Rape and kill the Bloodthirster and Keeper of Secrets leading the daemons. Well thought out plan all round.
Green-Eyed Monster: Horus, and of course, Slaaneshi Daemons and Fulgrim. Those primarchs can be jealous of each other and their father.
Heroic BSOD: The Traitor Legions have this as part of their strategy, knowing that the shock of betrayal will leave the loyalists at less than 100%. It works spectacularly with a lot of rank and file Astartes and more than a few Captains. The Primarchs on the other hand...not so much.
Hero Killer: The Space Wolves are this as the Emperor's weapon of last resort: a Legion designed to kill another Legion.
It's been strongly implied that they were responsible for the "erasure" of the II and XI Legiones Astartes from Imperial history, and why the Emperor selected them to take Magnus the Red into custody for breaking the Edict of Nikea. When Horus changed the order from "arrest" to "kill", the Wolves didn't question the change in orders because it's what they were made for. They would do it all again without a moment's hesitation.]]
Kasper Hawser: The unprecedented. Like... Astartes fighting Astartes? Like the Rout being called to sanction another legion?
Leman Russ: That? Hjolda, no. That's not unprecedented.
The censure of the World Eaters that comes up in Betrayer could also qualify. Angron mentions that he never figured out why Leman Russ is considered to be the Emperor's executioner. Some of the material that has come out since Prospero Burns has implied that the Emperor did not bestow the title of "executioner" upon the Space Wolves, but that they took the title and job upon themselves to give their Legion a "role" in the future, after the galaxy was fully conquered.
Hidden Depths: Perturabo turns out to be surprisingly cultured and artistic for a guy who specialises in knocking down fortresses.
Hive Mind: One example in Tales of a a psyker using hive-mind possessed empaths as a time-travelling communication device. It's more impressive because said psyker is actually a Pariah and an apprentice Sister of Silence.
Humans Are the Real Monsters: Being Warhammer 40,000, some of the nastiest and most brual creatures out there are wearing the Imperium's colors. After conquering a galaxy of other species, they start fighting each other.
Humiliation Conga: Erebus in Betrayer. Forced to seek shelter with his primarch, belittled by him in front of Argel Tal, Lorgar, and Kharn, and then beaten to bloody scraps by Kharn after murdering Argel Tal. Then when he finally makes it back to Horus, the Watmaster peels off his face for blaming him for the failure to bring the Blood Angels to the side of chaos.
Hawser: The...the Vlka Fenryka are capable of cannibalism? Skarssi: We are capable of anything. That is the point of us.
I Am Spartacus: All the Alpha Legion are Alpharius. It makes the scheming and unconventional warfare easier when the non-Legion don't know who's who. Taken Up to Eleven by the fact that not even the Alpha Legionaries are aware who's Alpharius at times besides Alpharius.
Do you remember how in 40K knowing a daemon's true name can give you power over it? It turns out the reverse is true. Prospero Burns has a Tzeentchian daemon tearing through Space Wolves left and right because it knows their true names from Kasper Hawser. The only ones who are immune are Hawser, because he didn't know his own name, and Bear, because that's what Hawser called him and not his real name.
Damon Prytanis pulls this on a daemon near the beginning of The Unremembered Empire, after tricking it into thinking that it knows -his- True Name
Immortality Hurts: As the Night Haunter demonstrates to Vulkan in Vulkan Lives. Constant regeneration can be awful.
Implied Death Threat: Vulkan's response to the Night Haunter's speech is to remind him not to leave hammers in his reach.
Infodump: The prologue of Descent of Angels is eight pages/twenty minutes of telling the reader about Caliban, its knightly orders, Lion El'Jonson, and his crusade to exterminate the great beasts.
It's All About Me: Horus, again. It's his Hersey. The Primarchs seem to have this as a trait generally.
When Angron's attack throws off his plans in Galaxy in Flames.
Horus was like this a lot in Horus Rising but when things go to hell, he claims that it wasn't his fault (which it wasn't). Then he decided he'd had enough and killed everything.
It Was a Gift: Every plot important Space Marine has one or two of these. Primarchs have them up the wazoo. They vary in importance from "offhand mention" to "will be referenced in another book" to "major overarching plot point".
Kick Them While They Are Down: The traitors do this a lot. Eidolon's attack in Galaxy in Flames intentionally starts with the wounded and The Medic. Lucius does it to Solomon Demeter in Fulgrim.
Knights and Knaves: Lorgar's encounter with Fateweaver in the Eye of Terror. While Fateweaver's two heads do speak a few lines of dialogue in unison telling the truth, which causes him some visible strain, one head does tell Lorgar about killing Guilliman and establishing himself as an equal to his brothers, the other tells him that that act would cost him his ultimate victory in The Long Game. In the events that follow throughout the millenia, it's never established which head was the one telling the truth.
Life or Limb Decision: Kapser Hawser is forced to cut off Bear's arm to save him from the daemon's magic fire.
Lighter and Softer: As amazing as this trope may seem, the earlier books in the Horus Heresy are much less Grimdark than the books later in the series and much, much lighter than the books taking place in the 41st millenium.
Mad Doctor: Apothecary Fabius of the Emperor's Children doesn't believe that his brother legionaries can achieve their primarch's ideal of perfection through strength of will and arm alone, so he tinkers with their biology, modifying organs and adding new ones when he thinks they can help, no matter the source. His alterations to Marius Vairosean made him the first Noise Marine.
Magic Music: The music on Isstvan III and in the Laeran temple (later adapted into the Maraviglia). They both make people go insane. The latter summons Slaaneshi daemonettes.
Meaningful Rename: Legions were renamed by their primarchs in the Back Story; the betrayed Sons of Horus (briefly) call themselves the Luna Wolves again; and Abaddon renames the Sons of Horus, to the Black Legion, at the end.
In Prospero Burns Amon Tauromachian was controlled by a daemon who claimed to be Amon of the Fifteenth Astartes, Captain of the Ninth Fellowship . He couldn't move and he was forced to speak the words put into his mouth. Supposedly, he was controlled so thoroughly because Puppeteer had the same name as him.
Kasper Hawser. Everything he saw and experienced was relayed to the daemon. His actions and memories were also subtly influenced.
More Than Mind Control: Kasper Hawser's life was subtly influenced by a Chaos daemon instead of the Thousand Sons like was first thought. The daemon could see and experience everything he did and influence his actions and memories.
Motive Decay: Horus suffers a bad case of "This is your motive on Chaos". He starts off with "prevent The Emperor from being worshipped as a god in line with the Great Crusade" to "burn the galaxy ".
My Eyes Are Up Here: Euphrati Keeler says this trope almost word-for-word to Ignace Karkasy in "False Gods"
Fulgrim suffers this at the very end when he kills Ferrus Manus.
Horus had one during his climactic duel with the Emperor during the Siege of Terra. In the brief moments before he was completely obliterated by the Emperor's psychic onslaught, the man Horus once was came back and he basically had time for this trope, followed by "I'm sorry"... and then he dies.
Downplayed and averted in Ages of Darkness. A loyalist Thousand Son attempts to "heal" (using his psychic powers to show him how wrong his actions were, and offering to remove the Butcher's Nails in his skull) Equerry Kharn of the World Eaters. He fails, but his last revenge before Kharn kills him is the knowing that Kharn will forever live with the knowledge that his betrayal was wrong (and that he could willingly have turned back). He then wonders what effect this will have on Kharn in the future. He then wonders what effect this will have on Kharn in the future...
A small side note; In the Great Crusade and Horus Heresy, Kharn was the comparative voice of reason and calm to his primarch. He only gained his reputation for being a tad touchy AFTER the heresy was over...
Not so much in the Heresy. Right after the Betrayal at Istvaan he's seen as a slavering lunatic, roaring about the Eightfold Path. This madness-on-the-edge-of-control continues into Age of Darkness' "Rebirth" where he's acknowledged as being changed into an utter madman, consumed by bloodlust. Although (presumably) in between these two stories he's seen as back to being rational in The Butcher's Nails, so it's anyone's guess how stable he is at any time.
This is presumably Khorne's little joke: the Blood God would probably be amused by the idea of turning the Legion's most restrained, stable and level-headed individual into a raving lunatic, if he wasn't so bloody furious all the time.
Kharn's team killing tendencies could be partly the result of being unable to mentally reconcile a berserker mentality with genuine guilt.
Naïve Newcomer: The Imperium, of all people. Most of the other civilizations they meet are flabbergasted when they learn the Imperials have no knowledge of Chaos or the dangers of the Warp.
Lion's extermination of monsters in Descent of Angels is revealed to have nasty consequences in Fallen Angels
The Emperor causes many messes. It's enough to think that he is either a idiot or wanted to end up on the Golden Throne.
His 'rebuke' of the Word Bearers and Lorgar. As pointed out in Novel its not like their religious aspect was anything new, So why wait so long to bring them to task, and why in such a public humiliating way to? Hell the fact that Magnus AND RUSS agreed that the rebuke was a bad idea smakes this all the clearer.
The Emperor made sorcery and psykers illegal, which Magnus the Red and his Thousand Sons legion reluctantly accepted. However, when Magnus foresaw Horus' betrayal, he broke his promise and contacted the Emperor directly via sorcery. The result? The Emperor sends Leman 'I Hate Written Knowledge' Russ to apprehend Magnus on Prospero, better known as the greatest library in the universe after the Black Library. Russ and company believe that the warning was an attempt by Magnus to scare the Emperor into allowing sorcery again, and proceed to destroy Prospero and force Magnus to turn to Tzeentch to save what remained of his legion.note the Emperor had only ordered Leman Russ to apprehend Magnus and the Thousand Sons. The reason why the Space Wolves fought the Thousand Sons was because Horus (already worshipping Chaos, but still "loyal" to the emperor) told Russ that the orders had changed from apprehend to kill.
The Emperor's plan for dealing with Chaos is to lie to and woefully underinform all of his sons, and his entire population, about what Chaos *is* (telling Horus, for example, that chaos "demons" are just random collections of emotions that have no real intelligence or guiding force), apparently forgetting that one of the major powers of Chaos is to literally plays chess with mortals. He didn't once think that the chaos gods would try to tempt the primarchs? Or that his lack of instruction on them would leave them largely defenseless?
In Angel Exterminatus, we find out the Emperor gave Perturabo some very specific advice. Rather then helping Perturabo avoid a mistake the Emperor almost certainly had foreseen, it ends up pushing him into Horus's camp after making the mistake. Perturabo was also more than a little annoyed that an arena he built for contests of strength and skill was used solely to humiliate Magnus, one of the few Primarchs he got along with. By direct order of the Emperor.
Ironically, Magnus broke it in the exact same situation as the Emperor. His warning obliterated The Emperor's work to open a gateway into the Webway, which would have allowed humanity to never have to use the Warp again. For that matter, it's heavily implied that it was Magnus's earlier pact with Tzeentch to save his Legion that was the deciding factor in the Emperor outlawing psykers.
Nice Job Fixing It, Villain: The assault on Calth and the Shadow Crusade was planned to wipe out the Ultramarines and trap the survivors in the ruinstorm. Instead, the Ultramarines earned a hard-won victory at Calth, withstood the Shadow Crusade and stayed safe while the galaxy went to hell, emerging as the strongest post-heresy power and led the counterattack after the Battle of Terra.
Nice to the Waiter: Horus was popular with the support crews, then he went off the deep end. Otherwise, a good sign between the good guys vs. the bad.
No Hero to His Valet: Averted- Every heroic figure is held in high esteem by all, except for the main characters. This is exemplified when a Legion's Space Marines generally have such a lofty opinion of their Primarchs that it borders (and crosses into) fanaticism.
Noble Demon: Perturabo has shades of this. During the events of Angel Exterminatus its stated that he does not hate the Loyalist Legions, just sees them as being used and abused by the Emperor as much as the Traitor Legions were. He also allows the crew of the Sisypheum to escape after they destroy Fulgrim`s flagship.
Not As You Knew Them: In 40K the Space Wolves are one of the nicer chapters in their relations with normal humans, especially civilians. During the Crusade, their reputation for ruthlessness, superstition and savagery against their foes made the Vlka Fenryka the most feared force in the galaxy, with some Imperial Army units considering defeat preferable to calling the Rout for help.
Maloghurst and Horus both turn up alive after their deaths seemed apparent.
As of the Audio Book 'Legion of One', it is confirmed that Garviel Loken is this too, as the Warrior Cerberus
Not So Different: Oddly enough, the Space Wolves and the Thousand Sons. Both suffer from a flaw that reshapes their bodies and minds into crazed killing machines, and both defied the Emperor's edict about psychic powers, although the Rune Priests justified it with their belief that their powers came from Fenris itself. Ahriman even drives Wyrdmake insane by demonstrating their commonality as psykers.
Not So Stoic: Roboute Guilliman is ordinarily the most level-headed, intellectual primarch, but when he learns the depth of the Word Bearers' treachery at the Battle of Calth he swears to kill Lorgar personally, even after admitting that it's not the best move tactically.
Obfuscating Stupidity: Space Wolves: Brutal, brain-dead Proto-Vikings in Space who do nothing but destroy in an uncontrollable fury? Nope - highly trained, ruthless, utterly unfettered battlefield analysts designed to kill another Legion, as The Emperor's Executioners
Old Retainer: Every Legion has at least one. They vary in plot importance and even background from book to book. Malcador is this to the Emperor.
One-Man Army: If normal Space Marines are this to humans, the Primarchs are this to Space Marines. We don't get to see it that often, but when the Primarchs let loose, they can be terrifying indeed.
Horus Lupercal in Horus Rising. When negotiations break down with the Interex, Horus picks up a fallen Luna Wolf's power sword and combi-bolter and says that if the Interex fears them, then the Luna Wolves are going to give the Interex a reason to fear them.
Angron in Galaxy In Flames: After virus bombing Isstvan III fails to kill the Space Marines who would have stayed loyal, Angron leads an assault force of the World Eaters and starts by tearing up his own former Legionarries. The assault is so violent that Saul Tarvitz, a Space Marine, actually runs away.
Then in Betrayer, he holds up a Titan's descending foot with his bare hands.
In A Thousand Sons, when Azhek Ahriman meets Leman Russ for the first time, the sheer amount of aggression emanating from Russ's aura is so strong it causes Ahriman a minor Brown Note and he has to cut himself off from the warp for a moment to keep from going nuts. The book also showed that Magnus the Red was quite happily able to go toe to toe with enemy titans when he wanted to.
Corvus Corax in The First Heretic: He takes on a small army of Word Bearers who have been possessed by daemons and cuts through them like they're paper. This is repeated later on in Raven's Flight when he takes on an armoured division of Iron Warriors and manages to kill most of them before what's left of his legion becomes involved. Notably he effectively beats a Predator tank to death with his fists then uses what's left of it to kill an enemy tactical squad.
Roboute Guilliman in Know No Fear: Fights for several hours on the hull of his flagship while in orbit low enough to have an atmosphere so thin only another Primarch could survive unhelmeted. All the while, he's killing Word Bearers on the hull with only his power fists.
Lion El'Jonson in Descent of Angels: He battles dozens of xenos which are actually daemons on Sarosh by himself without breaking a stride. Then in The Lion short story, he fights his way through dozens of daemons and concludes the incursion by stabbing Kairos Fateweaver, the most powerful Lord of Change in existence, in the heart.
Fulgrim in Fulgrim: He manages to cut through the Laer so fast that his own Terminator First Company cannot keep up with his kills. In the same novel, Ferrus Manus manages to cut through the Diasporex soldiers and get to their captain before Fulgrim can.
Mortarion in The Flight of the Eisenstein. When mowing down the Jorgall he decides that they're unworthy of being killed by his Manreaper, instead using the Lantern to kill them at will.
During the battle of Prospero Magnus uses his sorcery to inflict horrific deaths on hundreds of rock-hard Space Wolves. Then he uses them on Russ, which only makes Russ angry. You'd be angry too if a gigantic Cyclops broke your armor to pieces with cold fire, punched his fist through one of your hearts, stabbed a psychic blade through your chest and out your back, killed the wolves that you likely grew up with, and were blinded by a painful ray of black light. Magnus didn't go down like a chump against Leman Russ, that's for sure.
Sanguinius is finally unleashed in Fear To Tread: He takes out two Greater Daemons of Chaos within moments of each other: Ka'Bandha, a Bloodthirster of Khorne, by tearing off one of his wings and throwing him back into a Warp portal, and Kyriss, a Keeper of Secrets of Slaanesh, by cutting off his/her head.
Jaghatai Khan in Brotherhood of the Storm: During the final battle on Chondax, he is cutting through Orks like they are paper.
Perturabo does this several times in Angel Exterminatus. Every time he picks his hammer up, everyone in his general vicinity dies very, very quickly. He is considered such a threat that the crew of the Sisypheum were willing to self-destruct their ship if it would take him out as well.
Lorgar Aurelian in Betrayer. When Angron is buried under several tons of debris, Lorgar uses his psychic powers to kill several Ultramarines while trying to find Angron. Lorgar is barely looking at the Ultramarines while he does this.
Vulkan in Vulkan Lives. During the battle at the Urgall Depression of Isstvan V, he takes on whole squads of traitor Legionaries and even Dreadnoughts. Angron actually appeared during this time, and Vulkan was ready to charge the Red Angel by himself. Only an aerial bombardment forced Vulkan to retreat.
Konrad Curze in The Unremembered Empire: After spending three months evading the Dark Angels on their own flagship, Curze is able to escape to the surface of Macragge by orchestrating a drop pod assault. Once he gets inside the Fortress of Hera, he goes on a rampage, killing whole squads of Ultramarines and Dark Angels seemingly everywhere at once. The attacks are in such quick succession that the Ultramarines are half convinced that Curze brought several squads of Night Lords with him. When Roboute Guilliman and Lion El'Jonson finally corner him, he is moving so fast that two Primarchs cannot keep up with him.
Only Sane Man: The protagonists of each novel get to watch as things go to hell around them.
Tirin Maas believes he's this while the rest of Eisenstein's crew appears to turn against the fleet's orders at Isstvan III.
Our Dragons Are Different: The Void Dragon, locked under Mars by the Emperor after he found it weakened on Earth. Being C'tan, the only reason it's even called a "dragon" is that it chose that form on Earth.
Outgrown Such Silly Superstitions: "The Imperial Truth". It would be great if those pesky daemons didn't keep popping up. The Emperor has a really good reason to try and quash knowledge of Chaos but unfortunately, Chaos isn't strengthened only by active worship. It is the collective embodiment and manifestation of the emotional output of every sentient being in the material universe, so the Imperial Truth wasn't starving Chaos as it was intended so much as reducing its servings slightly. It turns out that the only real way to counter it is with an alternative object of worship.
Horus, the Primarch and favored son of the Emperor is now a traitor that took a huge chunk of the Imperium with him.
Ironically, Horus thinks The Paragon is really Sanguinius. It's why Horus tells Ka'Bandha to kill Sanguinius in Fear To Tread, both because Horus knew, deep down, that the Chaos Gods couldn't corrupt Sanguinius, and also because turning Sanguinius would result in a possible rival to Horus's leadership of the Traitor Legions.
Erebus opines that it's Guilliman, predicting he would be the one to take over if something happened to the Emperor. He's right.
Averted by Lord Commander Vespasian of the Emperor's Children, who pre-heresy was considered a model Astartes and had no vices or desires the Slaaneshi daemon could use to corrupt him.
Parental Favoritism: The Primarchs all have their rivalries, their favorites, and the Emperor does as well.
Pay Evil unto Evil: Multiple times the Horus Heresy paints the Emperor as, bluntly, an arrogant prick who held a great deal of responsibility for his sons falling and the heresy occurring in the first place. He waits a century before censuring Lorgar for establishing the Imperial Cult on conquered worlds, while simultaneously humiliating the Primarch and the entire Legion and destroying the innocent inhabitants of a world to make a point. He refuses to explain to Horus why he is leaving the Great Crusade, despite their closeness and the obvious damage the lack of trust did to his most favoured son. Magnus the Red arguably fared worst of all, as the Emperor specifically sends Russ and the Space Wolves, a Primarch and Legion who loathe Magnus and the Thousand Sons to their core to bring Magnus back to Terra, making it child's play for Horus to change the order to one of extermination.
People Puppets: Prospero Burns. The daemon controls people with their names.
Personal Effects Reveal: Horus Rising when Captain Loken finds a lodge badge; The Flight of the Eisenstein, when Garro goes through Kaleb's possessions.
All of the Primarchs are superhuman warriors of peerless might, capable of cutting through hundreds of times their number in Space Marines.
Magnus, as the most powerful psyker in the galaxy short of his father, can kill a hundred Marines with a glance, destroy Titans with a hurricane of Psyflame, and even raze the surface of a planet by bringing the Immaterium into realspace.
This is sort of the hat of the Thousand Sons in general, captains of the Thousand Sons could easily kill Space Wolves and even Custodians with their potent sorcery (Phosis T'kar remarking on how unimpressed he was with the prowess of the Custodians), and at one point a Thousand Son channels so much of the Warp into him that he goes off like a miniature supernova, annihilating everything within a ten kilometer radius.
Lorgar Aurelian, post Istvaan V, also becomes a very powerful psyker, capable of crushing Titans with his telekinesis and bringing down Thunderhawks with a glance.
Place Beyond Time: The Immaterium and Horus' visions during his time in the Temple of the Serpent Lodge.
The only immediate conclusion that can be drawn about primarchs 2 and 11. They are mentioned several times, but characters talking about them are either interrupted by other characters or stop conveniently short of revealing something important about why they are not around any more. The series is also sprinkled with hints about what may have happened to them and their legions. Leman Russ implied that the Space Wolves had been ordered on to fight another legion before the burning of Prospero and an operative of the Vanus temple has been called on to eliminate at least one "Brother Captain". There are theories given in universe. The most popular one is that the two spare legions were subtly dispersed into the Ultramarines, explaining why there were so many of them.
In The First Heretic temporally displaced Word Bearers witnessing the creation of the primarchs contemplate pre-emptively killing the XI primarch to avoid the (implied) bloodshed that will happen when the legion is purged.
Hastur Sejanus has strong elements of this in Horus Rising and False Gods.
The Power of Friendship: A few friendships made cross-legion prove to be stronger than the marines infamous loyalty to their Primarch.
Power of Trust: A running theme through the series, and a big part of the opening trilogy is just who the loyalist marines can trust.
Praetorian Guard: It seems most of the Primarchs (though by no means all, Horus doesn't, for instance) have some form of Honour/Praetorian Guard. Horus does officially have one in the Justaerin terminators, but they're mostly battlefield elite.
The Custodes are this to the Emperor, and sometimes serve in special assignments to the emperor.
Mortarion's Deathshroud Terminators, who first appear in the series in Flight of the Eisenstein.
Fulgrim's Phoenix Guard, and Ferrus Manus's Morlocks, who have something of a malignant rivalry after Fulgrim's failed attempt to convert Ferrus Mannus to Horus side (before the heresy began in earnest), and the cadre of Pheonix Guard quite literally murdered their counterparts in the Morlocks to escape.
Rogal Dorn's Templars.
Lorgar created one, the Gal Vorbak, fairly late, roughly 50 years before the start of the Heresy. They were formed from the surviving Astartes "expidition force" that returned from their excursion into the Eye of Terror, and came back...[Demonic Possession changed]].
Rejected by Lorgar in Betrayer, who has seen visions of Sanguinius dying at Signus, falling to Chaos, and fighting at Terra. While Erebus is convinced that they can either kill or convert Sanguinius, Lorgar rejects the visions they have both seen of the first two and says that the third is what will come to pass, because he knows his brother better than Erebus. However, one of the great ironies of Betrayer is that Lorgar actually doesn't know his brothers as well as he thinks he does.
Embraced by the Cabal with "the Acuity", a form of divination based on Eldar farseeing. In Legion, they reveal to Alpharius and Omegon that if the Emperor wins the Horus Heresy, the Imperium will stagnate and collapse after ten or twenty thousand years, where humanity will fall to the Chaos Gods. However, if Horus wins, a remnant of his original personality will emerge at the grief he experiences and basically wipe out the humans in a self-destructive crusade, taking the Chaos Gods with humanity, which convinces the Twin Primarchs to ally the Alpha Legion with Horus. The Cabal maintains that the Acuity is flawlessly accurate, but in Vulkan Lives, Eldrad Ulthran, a real Eldar Farseer, indicates that it may be wrong, and that a military victory for the Imperium may be the best outcome.
Purple Prose: The writers really cut loose when called upon to describe the Primarchs or the Emperor Himself.
At the end of Galaxy in Flames, Loken and company make damn sure Horus's victory costs him.
n Know No Fear, Calth is technically a victory for the Ultramarines because they survived, but they had to really bleed for it.
Reasonable Authority Figure: Jaghatai Khan, full stop. Cut off from communications with the rest of the Imperium. Suddenly gets two diametrically opposing messages, one from Horus stating that his best friend Magnus just had his legion wiped by the Space Wolves, another from Dorn stating that Horus (the only other Primarch Jaghatai ever got along with) has turned traitor. What does Jaghatai do? Take a Third Option by visiting Prospero and seeing for himself what happened before deciding on a course of action.
Rebellious Rebel: Cutting this off was the reason for the Isstvan V attack — and fomented it among the survivors. Also Garro, and the crew of the Eisenstein.
Subverted with Sigismund in Mechanicum. While he really, really wants to lead the Imperial Fists on a revenge spree against the Dark Mechanicum and kill everything standing between him and Kelbor-Hal, Sigismund ultimately realizes that Rogal Dorn's orders to secure Space Marine arms and armor from Mars is more important. He's really displeased about it.
Played straight with Roboute Guilliman in Know No Fear. When learns that Lorgar deliberately orchestrated the Campanile crash, Guilliman informs his subordinates that the Macragge's Honour is going straight for the Fidelitas Lex. When he's called on it, Guilliman tells Gage that he knows that it's tactically dangerous to try and board the enemy's flagship this early, he just doesn't care.
Right Makes Might: The original Imperial Truth, as explained and invoked by name by the senior iterator (indoctrination/political officer and teacher of such) Kyril Sindermann in Horus Rising.
Royal Brat: The Emperor's sons leave much to be desired in terms of maturity. See all that resentment and pride etc.
Roaring Rampage of Revenge: The Loyalist Primarchs are down right terrifying when they start letting out the anger the Heresy is causing them on Traitor Space Marines.
Ferrus Manus in Fulgrim. When the traitor legions begin their false retreat during the Drop Site Massacre, he refuses Corax and Vulkan's advice to fall back to rejoin the other four Legions, and instead orders the Iron Hands to advance while the Raven Guard and Salamanders fall back to resupply, all while grabbing any traitor Legionary who tries to run away and takes them apart with his hands.
Corvus Corax in The First Heretic. His Legionaries being cut down by the thousands, he tears through dozens of daemon possessed Word Bearers like a hot knife through butter, and would have killed Lorgar if not for Konrad Curze. All while shrieking—literally, shrieking like a bird of prey—in rage. Lorgar is utterly horrified to see Corax so enraged.
Roboute Guilliman in Know No Fear. The stoic master of warfare as a science goes absolutely wild on Word Bearers trying to board his flagship, beating them to death with nothing but his bare fists. That's right, no Gauntlets of Ultramar! He does all this while on the hull of the ship without wearing a helmet.
Sanguinius in Fear To Tread. With Ka'Bandha and Kyriss responsible for the deaths of hundreds of his sons, he throws Ka'Bandha through a warp portal and decapitates Kyriss, both of them with ease.
Vulkan in Vulkan Lives. When the four Legions turn on the Loyalists, Vulkan charges ahead of the Salamanders and uses his hammer to send Rhinos and Land Raiders flying through the air.
Self Fulfilling Prophecy - Horus rebelled because he had a vision where the Emperor became the God Emperor and wanted to prevent such a thing. His actions lead to Emperor in his Golden Throne as an object of worship.
Serial Escalation — It's Warhammer 40,000, which has been using this for decades, so it's only natural it starts happening. Specifically, this is the pre-heresy hat of the World Eaters Legion: to be willing to go one step further than the enemy will go.
Serrated Blade of Pain — The signature weapon of the Blood Angels Fifth Company are serrated combat knives used for flaying. They end up being the first Space Marines of the Flesh Tearers chapter.
Present among the Primarchs. When Horus was appointed Warmaster, he believed that only Sangiunius, Rogal Dorn, Fulgrim, Mortarion, and Lorgar geniunely supported the decision, with the other doing so reluctantly. Petronella Vivar was shocked when Horus told her this, but he responded that they may be family, but they're still siblings, and all siblings try to outdo the other to impress their parents.
The Lion and the Wolf had a particularly violent spat over engagement procedure. Dorn and Perturabo had a...disagreement about the defensibility of the Imperial Palace (oh irony). Roboute Guillman, Paragon of the Standard Procedure, outright denounced Alpharious, Master of the Unorthodox and Decentralised leadership.
Sinister Minister - In the backstory, Cardinal Tang, who is Hitler in the distant past/far future of the 29th Millennium.
Smug Super: The Night Lords Legion with regards to their human "allies". In flashback to the Great Crusade in Vulkan Lives after pacifying a planet with the Salamanders Legion where Konrad Curze went behind Vulkan's back and wiped out the population of the the planet's capital, the Night Lords take time to intimidate the Imperial Army officers and the Administratum adepts. Half of the Salamanders Pyre Guard want to drag the Night Lords into the practice cages and see how they would do on even ground. The other half of the Pyre Guard just want to turn their flamers on the Night Lords.
A Storm Is Coming - Before the occurrences of Isstvan III's destruction, the warp is turbulent and heralds a great turbulence in reality.
The Strategist - Besides the Primarchs being peerless generals, this is part of the hat of the Ultramarines Legion: go into every battle with a theoretical (a sound understanding of what the situation is) and a practical (a solid plan of attack).
Stuff Blowing Up: All over the place - this is Warhammer 40,000 after all - but special mention goes to Know No Fear. The initial phase of the Battle of Calth has Dan Abnett channeling Michael Bay, with a commandeered ship utterly destroying Calth's space dock, a twelve-kilometer grand cruiser crashing into a city and demolishing it, and the destruction of a low-orbit depot causing a group of Ultramarines to experience a rain of main battle tanks.It's all described in loving detail, and it is awesome.
Super Soldier - Considering that this is the age of the Space Marine Legions, this is emphasised a lot. However, the Primarchs exceed all expectations and then some. Even more scary are the Proto-Astartes. Not a lot is known about them, but the two that survived up to the Horus Heresy were considered badass even by Space Marine standards. Whilst the Space Marines were created with the idea of being an elite fighting brotherhood united in arms for the good of mankind, the Proto-Astartes were brutal borderline psychopaths with loyalty solely to the Emperor. He repaid them with a bloody post victory program after the conquest of Terra.
Swiss Army Superpower - John Grammaticus in Legion, among other things, a high-functioning logokine, which is apparently psyker who's powers have an emphasis on spoken language. While he has shown several of the standard psychic powers such as sensing psychic phenomena and a mild telepathic ability, he can tell when someone's lying, tell precisely where someone is from based on their accent, understand languages he's never heard before, use his voice to trick people into something they aren't seeing. Amongst other things.
Teeth-Clenched Teamwork - Sometimes, it seems like the only thing keeping the Traitor Legions together is the Primarchs and the only thing keeping the Traitor Primarchs together is Horus. Corax forms part of his strategy around it, believing that if the Raven Guard attack behind enemies lines and slow the Traitors advance, they can delay the inevitable attack on Terra, causing cracks to form between the Traitor Legions and they'll turn on each other. It happens, just after the Siege of Terra.
Tele-Frag: Happens to several Ultramarines when they board an orbital platform to kill Kor Phaeron and restore Calth's orbital grid.
Age of Darkness reveals that Guilliman is training his forces to fight all legions, both loyal and traitor, and is formulating some sort of plan known as "Imperium Secundus". Whether this is to preserve something of the Emperor's dream or replace the Emperor is up for debate, as we still don't know what Guilliman's ultimate intentions are.
As of The Primarchs, Omegon is plotting behind Alpharius's back.
To Be Lawful or Good - The Emperor's Children had to decide whether to follow their orders and colonize some exceptionally beautiful planets, ruining their beauty, or to pass them by. After its revealed that the planets are Eldar Maiden Worlds and Eldrad accuses Horus of treason, Fulgrim takes a third option and virus bombs the planets into nothing.
Took a Level in Jerkass: While generally considered a moral paragon by the standards of Warhammer 40,000, the novels show that the Emperor was a bigger prick than anyone realized. Emps really did not stop to think too much about how ordering people to do things and never telling them why might turn out in the long run.
In The First Heretic. It was established that the Emperor chastized Lorgar for his religious zeal, but what wasn't established was how he made his point before doing so. He ordered the Ultramarines to completely wipe out a complacent city that the Word Bearers had converted to his worship. These people had done nothing else, but were destroyed solely to provide an example of what would happen to those who engaged in religious practices.
Horus' sorrow and growing insecurity are over the Emperor up and leaving, going home to Terra and telling him, his favoured son, absolutely nothing about why.
In Mechanicum, he appears on Mars, demands the planet's allegiance, seals a tomb of ancient technology and erases the Fabricator-General's memory of where it is - but not, for some baffling reason, his memory of Emps being a giant dick to him. Guess who led over half of Mars into rebellion a couple hundred years later?
Too Dumb to Live - The people on Horus's ship when he was brought back from Davin, critically wounded. Yes, the entire point of the scene was to point out that the Mournival and the Luna Wolves as a whole were starting to lose their grip on reason, and there was some well-deserved My God, What Have I Done?, but the slaughter that was supposed to be the edge of the Moral Event Horizon for the legion wouldn't have happened if hundreds of worried people hadn't flooded the clearly demarcated path between the docking bay and the hospital and continued to push in to try to see Horus's wounded body themselves, even as the raging Marines went from shoving people to punching them, stepping on them, and assaulting them with weapons.
Tranquil Fury - Inverted by Angron, who drives himself into such huge fits of rage that it turns him insensate to the point that it's almost a trance, which are the only times he gets Zenlike periods of peace.
Konrad Curze is also like this, as well as Alpharius to an extent, due to their sneaky, secretive natures. Although to his credit, Alpharius doesn't give a damn in the slightest.
Angron is also unpopular among his brothers.
A rare loyalist example with the Khan. Apart from Horus and Magnus, none of the other Primarchs especially like him due to his distant nature and isolationist behaviour. Even the Emperor admits (a little regretfully) that this is case, although it was intentional.
The Unfettered - It doesn't matter what the Emperor asks, the Rout will carry it out; that's what they do. Angron calls Russ out on this.
Unfriendly Fire: False Gods has a particularly nasty example which is only revealed after the act due to the chaos of battle, when Horus has the army leader killed.
The Unmasqued World: The "Imperial Truth" couldn't hold up against all the demons and chaotic gods running around and messing with people.
Unstoppable Rage: The Blood Angels go into the Red Thirst en masse when Ka'Bandha kills five hundred legionaries and the psychic backlash sends Sanguinius into a coma. Unfortunately, it works too well, to the point that Daemons of Khorne are unable to fight off the Blood Angels.
Unusually Uninteresting Sight - In Know No Fear, Captain Ventanus notes that Sergeant Anchise's efforts to rally and redirect the remnants of the Ultramarines' 111th and 112th companies would normally become the stuff of legend. On Calth, it's simply another man's struggle before his death. It becomes much more interesting when those two companies become the backbone of the group that ends up reinforcing Ventanus in the end of the book.
The Uriah Gambit: False Gods sees Horus use the comotion of battle to kill an army leader.
Utopia - The Great Crusade and in general the Imperium of Man seek to achieve this. Alpha Legion Astartes have a heyday philosophically playing around with this concept.
Kyriss goes absolutely insane when Meros takes the ragefire into himself so that Sanguinius doesn't. He (she?) begins screaming in tongues and begins shouting that the Blood Angels are merely pieces on the board with no right to rebel. Sanguinius ends up decapitating it in the midst of its breakdown.
After spending the entire series as the most calm, collected, and unemotional of Chessmasters, Erebus goes off his rocker and verbally rips into Horus for interfering with the trap for the Blood Angels and courting the displeasure of the Chaos Gods, only realizing his mistake after he had let loose verbally on the Warmaster. Horus's response is actually pretty tame for a Chaos corrupted Primarch: he skins Erebus's face off and reminds him that he is commanding the rebellion, not the Chaos Gods.
Betrayer reveals that Erebus's breakdown started even earlier. After screwing up the attack on Calth (earning a mocking dismissal by Lorgar), Erebus gets back up to his old manipulations again. His ego as "Destiny's Hand" is shattered when Lorgar tells Khârn that Erebus was responsible for murdering his best friend. Khârn then utterly curbstomps Erebus in a duel to the death. Erebus cannot actually mentally comprehend that this is happening to him before he escapes.
Ingethel has one in Aurelian during Logar's trip into the Eye of Terror when Khorne decides to test Logar in hand-to-hand combat with a Bloodthirster. To give an example of how bad this is, Ingethel, who is a Daemon Princess, is reduced to a sobbing wreck, repeatedly saying "Kharnath has violated the accord, Kharnath has violated the accord".
Vision Quest - The Temple of the Serpent Lodge sends one to Horus that radically alters his motivation and then him on a quest of conquest.
Voice with an Internet Connection - Revealed to be the specialty of the Vanus Templenote This was originally an in-joke on the part of the developers, as "vanus" is latin for "empty", meaning that in the 41st millennium, there was no 6th temple.
Was It Really Worth It? - Usually, if asked this, most traitor marines reply with "Yes" and a bolter to the face. Implied by the Eldar that, were he to win, Horus's grief and remorse would overcome him, causing him to declare war on.. everyone left, in shame. Perhaps most disturbingly of all is that Horus going mad with grief and slaughtering the ENTIRE Imperium of Man... might be the best possible outcome of the Heresy!
We Hardly Knew Ye: Ferrus Manus, who appears as a major character in a total of one novel and two short stories set before that. Fairly justified since his biggest role in the heresy was dying during the first major battle between loyalist and traitor forces (or the second battle, depending on who you ask).
"Well Done, Son" Guy - At least half the Primarch are like this, notably Konrad Curze, who became evil for the Emperor. Too bad the Emperor is kind of a dick.
Wham Chapter: When The Emperor makes an appearance, it usually has huge repercussions for the greater narrative.
Kai Zulane: But you're going to die. The Emperor: I know.
A Wizard Did It - An in universe example in Prospero Burns. Kasper's mind is altered by an alien force. When a Rune Priest enters his mind and finds details of Horus's betrayal, Leman Russ assumes that the prophecy was just implanted by the Thousand Sons as a ploy. He doesn't understand how that would work.
Wicked Cultured - Horus is a nice guy. Fulgrim is a patron of the arts. Magnus really likes books and libraries. Lorgar is said to be at heart more visionary and philosopher than warrior, as much as a guy with a giant spiked mace can be. Surprisingly, Perturabo has a solid grounding in Olympian classical myth and is capable of incredible feats of civilian architecture such as theatres and arenas.
With Great Power Comes Great Insanity - None of the traitor Primarchs are all quite there before selling out to the Ruinous Powers. Some, like Fulgrim and Horus, are given brief moments of lucidity to be horrified at what they've become, before the veil falls back down.
Woobie, Destroyer of Worlds: Seeing Angron reminisce about his comrades who had just recently died, punctuated by groans of despair, is pretty heart-wrenching.
Warsingers use their (heavily implied to be Slaaneshi-given) powers to create deadly magical effects through their singing. Also, Eidolon and the Noise Marines.
Invoked in Prospero Burns, where in a flashback we are re-introduced to Abnett's reality warping proto-language, Enuncia. Using it murders someone and causes the invoker to bleed from the mouth This becomes a Chekhov's Gun when Kasper Hawser uses the word he heard Murza say to to blow up a daemon's head.
World With A Dark Secret: The Emperor locked the Void Dragon on Mars sometime in the 10th or 11th century (of the second millennium) because he knew that technologically inclined humans would one day settle it, and proximity to the Dragon would inspire them to design things for humanity's betterment.
The Butcher's Nails leave those who suffer them mentally unstable, twitching, and unable to properly sleep. However, it gives Angron a type of serenity that he values.
In Know No Fear Lorgar says that the entire Battle of Calth was worth it just to see Roboute Guilliman lose his temper.
World Gone Mad: After being told about the Horus Heresy, Roboute Guilliman says that either Lorgar is insane, or the universe has gone mad. The sad thing is that since this is Warhammer 40,000', the first part of Guilliman's statement is true. The scary thing is that since this is Warhammer 40,000, the second part of Guilliman's statement might be true.
Initially played straight, but as the books go on, things change like during the virus bombing of Isstvan III. They ARE Space Marines, after all.
Most commonly averted by the World Eater/War Hounds Legion; Angron is depicted pretty consistently as undiscriminating when choosing targets.
Wound That Will Not Heal: Possibly the most major plot point in False Gods, referred to in most other works. A stab wound with a primitive blade shouldn't even slow down a legionary, let alone a primarch, and such a wound should heal rapidly, yet when Eugan Temba stabs Horus in the shoulder with the anathame in False Gods, his superhuman metabolism refuses to repair the damage or successfully fight the plague in the wound. Erebus tells the Mournival that the Serpent Lodge on Davin knows how to save his life and they take him there.
Year Inside, Hour Outside: Time does not flow at the same pace in the Warp as it does in realspace. Argel Tal experienced six months in the Eye of Terror in The First Heretic while less than a minute passes outside.
You Can't Fight Fate: Ultimately the revelation Magnus the Red comes to near the end of A Thousand Sons. All that has happened and will happened was preordained by the Architect of Fate, Tzeentch, every aspect of his life since he bargained with the Chaos God to save his Legion. The only thing he can do is try and be content with the part he has to play.
You Have Failed Me: Retroactively: When Perturabo took command of the IV Legion, he found it wanting and ordered it decimated.
You No Take Candle - Scars and Brotherhood of the Storm establishes that Korchin (the language of Chogoris) and Imperial Gothic are incompatible. As a result, White Scars from Chogoris will speak in rather fractured Low Gothic. When speaking in Korchin, they are eloquent.
0% Approval Rating - The Imperial forces aren't happy to see the Space Wolves in Prospero Burns.