History Fanfic / TheImperialHeresy

** Most original loyalists remains loyal to the Emperor (now, they're called "imperialists"), and, thus, becomes evil and corrupt when he falls to Chaos. The only exception is Vulkan, who's too pro-human to stay with someone who uses them as [[HumanSacrifice sacrifice to Chaos]], so he sides with ([[AdaptationalHeroism now-good]]) Horus instead.

** As in canon, the World Eaters still used butcher's nails, with all the "nice" effects on their sanity. Unlike canon, they never fully embraced massacre for the sake of massacre, and, after the Heresy, ditched using the butcher's nails completely (and even managed to remove the ones already installed), [[DefiedTrope specifically]] to not repeat the fate of Blood Angels, in whom they saw their possible future if they would allow their wrath to overwhelm them. Those who never dealt with their rage (like Angron himself) have leaft to the Eye of Terror to continue fighting Chaos.

* TheCavalry: Due to successfully dealing with Space Wolves attack on Prospero, the Thousand Sons managesto assist in defending Mars, arriving just in time to stop the imperialists from releasing the monstrosities hidden deep below.

* TheCorruptor: Lorgar made the Emperor vulnerable to temptations of Chaos by telling him that he can better protect Mankind if he becomes a god.

* ForWantOfANail: After Nikaea (where usage of psychic powers was forbidden, as in canon), Magnus sees the Emperor's judgement as mistake, and gives an oath to himself to prove it. Thus, he remains on guard and, when Horus gets hit on Davin, in Lorgar's attempts to corrupt him, Magnus is able to save him and prevent his fall to Chaos. Horus now being his ally results in Magnus being warned about attack of Space Wolves, and repel it.

* HitAndRunTactics: The main forces of the Word Bearers get distracted from the Siege of Terra, being too busy fighting the Night Lords, who attack them from the shadows only to retreat before they can do anything.
* HufflepuffHouse: Not all Imperialist Legions receives as much attention as the others, but the Space Wolves gets it worst. The only two conflicts involving them which get mentioned are the battle for Prospero (which they lose) and the cleansing of their homeworld, both barely described; the only thing known about their current state is that they're Nurgle worshippers.

** Just before his defeat at the hands of Horus, the Emperor was enhanced with powers of the Warp, making him into something truly monstrous, both in terms of power and in terms of how ugly he'd became.

* LeeroyJenkins: Vulkan has to be persuaded to not rush to Terra to save its populace right now, before rebels gets ready to besiege it.
* MutualKill: After killing the Emperor, Horus succumbs to his wounds and dies. However, later it turns out that the Emperor wasn't ''truly'' killed yet, and instead sits on the Black Throne in the Eye of Terror, which prevents him from dying at the cost of blood which spills during the Black Crusades.

* ProHumanTranshuman: The Salamanders sides with Horus, remaining protectors of Humanity first and foremost. During the Siege of Terra, they specifically dedicate themselves to protecting civilians from the rampaging Emperor's Children, which costs them ''enormous'' casualties. Nowadays, they're often called "the Angels of Mercy".

* TheStarscream: Heavily {{implied|trope}} with Guilliman, who doesn't bother with assisting the Emperor during the Heresy, awaiting for results of the Siege of Terra and to see who will come out on top, while dedicating this time to reinforcing his own empire. After the Heresy, he manages to preserve Ultramar, instead of running away to the Eye of Terror, albeit Guilliman himself is mortally wounded by Angron, and the Ultramarines have pledged themselves to... Malal.

* TokenEvilTeammate: Angron and the World Eaters are mostly the same as their canon pre-Heresy counterparts. They only ditched their berserker ways after seeing what they can become in the Blood Angels, who turned to Khorne.

** Abaddon gets forced to take over as new leader of the Imperium after the Emperor's defeat. He eventually stepped down due to old age.

** Most original loyalists remains loyal to the Emperor (now, they're called "imperialists"), and, thus, becomes evil and corrupt. The only exception is Vulkan, who's too pro-human to stay with someone who uses them as [[HumanSacrifice sacrifice to Chaos]], so he sides with ([[AdaptationalHeroism now-good]]) Horus instead.

The "alternate Heresy" fic, written and published on [=4chan=] subforum /tg/. It can be accessed [[https://suptg.thisisnotatrueending.com/archive/2011/16830576/ here]], with epilogue available [[https://web.archive.org/web/20201112031152/https://1d4chan.org/wiki/The_Imperial_Heresy here]].

*** The Mortifactors are a Successor Chapter of the Death Eaters instead of the Ultramarines.

The "alternate Heresy" fic, written and published on [=4chan=] subforum /tg/. It can be accessed [[https://suptg.thisisnotatrueending.com/archive/2011/16830576/ here]], with epilogue available [[https://1d4chan.org/wiki/The_Imperial_Heresy here]].

* ApologeticAttacker: Horus, after killing Sanguinius, says "forgive me", as no matter what he had become, this is still his beloved brother.

** Raven Guard (who became Tzeentch worshippers on their own initiative) are now mortal enemies with Night Lords, and frequently clashes with them.
** Ten thousand years after the Heresy, Blood Angels are still after the Sons of Horus, whose Primarch had killed theirs.
* AnArmAndALeg: Abaddon had lost both hands, replacing them with bionics. One of them was cut by Jaghatai-Khan himself, who's now a Daemon Prince.
* TheAtoner: Luther has leaved after the Heresy, receiving way too much blame for failing to show up for Siege of Terra. It's believed that he's wandering around the galaxy, trying to redeem himself.
* BackFromTheBrink: There were 80 000 Salamanders before the Heresy. After the Heresy, remained around ''400''. They managed to rebuild and eventually even create successor Chapter (Black Hoods) only by M33 (though in this fic, Chapters are ten times bigger than in canon).

** The Imperial Fists have fractured after the Heresy. More sane ones followed Sigismund and turned Black Templars, while others turned Khorne worshippers and formed Crimson Fists.
** As in canon, World Eaters still used butcher nails, with all the "nice" effects on their sanity. Unlike canon, they never fully embraced massacre for the sake of massacre, and, after the Heresy, ditched using the butcher nails completely (and even managed to remove the ones already installed), [[DefiedTrope specifically]] to not repeat the fate of Blood Angels, in whom they saw their possible future if they would allow their wrath to overwhelm them. Those who never dealt with their rage (like Angron himself), have leaved to the Eye of Terror to continue fighting Chaos.

** Attempt to corrupt Horus on Davin still happens, but it fails due to intervention of Magnus, Curze and Alpharius, who are now aware of dangers of Chaos.

* TheCavalry: Due to successfully dealing with Space Wolves attack on Prospero, Thousand Sons manages to assist in defending Mars, arriving just in time to stop the imperialists from releasing the monstrosities hidden deep below.
* CavalryBetrayal: The first three Legions to attack Horus and his forces on Isstvan V (Sons of Horus, Death Guard and World Eaters) are Iron Hands, White Scars and Raven Guard. The rest of forces (Dark Angels, Night Lords, Iron Warriors, Alpha Legion) attacks next... and sides with Horus, resulting in imperialists being massacred, and only escaping due to help of traitors amongst rebel forces, who provided them with one of their ships.
* CavalryRefusal: Ultramarines don't bother with going to aid the Emperor on Terra, preferring to wait till both sides weakens each other, likely with intentions to finish off the survivors. It results in Alpha Legion and Thousand Sons attacking them first.

** Luther and his part of Dark Angels are now explicitly defecting ''from'' the bad guys, not the other way around.
** Some elements of imperialists Legions chose to turn loyalists. In particular, Space Wolves had enough of such turncoats to even make a successor Chapter, Solar Wolves, led by Bjorn the Purehanded. It had since vanished, however, and their fate is unknown.

** {{Averted|Trope}} with Prospero; unlike canon, Thousand Sons ''do'' manage to protect their homeworld against the Space Wolves, due to Horus warning them about attack, and them preparing adequate defence.
** Cthonia was destroyed during the Heresy; losing their homeworld, the Sons of Horus now bases on Cadia.
** While it's safe to assume that all homeworlds of Imperialists were purged during Long War, Purging of Fenris is mentioned specifically, as the event which led to scattering of Space Wolves and disappearance of Leman Russ.
* TheDragon: With Emperor embracing Chaos and [[GodhoodSeeker following Lorgar's temptation to start pursuing godhood]], Lorgar became not just the prophet of Chaos, but the prophet of Emperor specifically, whom he praises as the fifth Dark God, despite him being yet to ascend.

** Lorgar became the most trusted servant of the Emperor, spreading the Word of Chaos in the Emperor's name. After Emperor's defeat, Lorgar continued leading the Black Crusades, with explicit purpose of spilling enough blood to fuel Emperor's ascension.
** With Rogal Dorn's whereabouts unknown, Sigismund had formed Black Templars to continue crusades against the New Imperium. Those who didn't follow him, formed Crimson Fists instead.

* DwindlingParty: Every five hundred years, the veterans of the Siege of Terra comes to honour the memory of heroes who died to put down the Imperial Heresy -- Horus, Mortarion and Malcador. Every time, their numbers dwindles; ten thousand years later, Abaddon is the last one still alive.
* TheEngineer: After the Heresy, Iron Warriors used their expertise to not only fortify both Terra and Cadia, but also reform Mechanicum.
* FaceHeelTurn: Emperor gets corrupted by Lorgar, and decides that there's no hope to defeat Chaos, so may as well join it and become the Chaos God yourself.
* ForWantOfANail: After Nikea (where usage of psychic powers was forbidden, as in canon), Magnus sees it as mistake, and gives an oath to himself to prove it. Thus, he remains on guard and, when Horus gets hit on Davin, in Lorgar's attempts to corrupt him, Magnus is able to save him and prevent his fall to Chaos. Horus now being his ally results in Magnus being warned about attack of Space Wolves, and repel it.
* GodhoodSeeker: Lorgar convinces the Emperor that he may become a fifth Chaos God. His attempt to do that -- and Horus to stop him -- replaces the original Horus Heresy; Lorgar still tries to achieve that result for him even long after the Heresy.
* GoodCounterpart: As Custodes went evil along with their master, they were replaced with new group, Golden Aquilias, who are tasked with protecting the rebuilt Palace.

** Robaute Guilliman kills Alpharius during conflict in Ultramar. [[NeverFoundTheBody Presumably]].
** The Emperor kills Mortarion and Horus during Siege of Terra.

* HeroWithBadPublicity: World Eaters have improved after the Heresy, and ditched usage of the butcher nails, but it did little to improve their reputation. Their successor Chapters seems to be more lucky in this regard.
* HitAndRunTactics: Main forces of Word Bearers gets distracted from the Siege of Terra, being too busy fighting Night Lords, who attacks them from the shadows, only to retreat before they can do anything.
* HufflepuffHouse: Not all Imperialists Legions receives as much attention as the others, but Space Wolves gets it worst. The only two conflicts involving them which gets mentioned are battle for Prospero (which they lose) and cleansing of their homeworld, both barely described; the only thing known about their current state is that they're Nurgle worshippers.

** Jagathai-Khan and Rogal Dorn both have ascended into Daemonhood, becoming Daemon-Princes.
* HumanSacrifice: Massacre of Terra population still happens, but now it's the Emperor who does that, as a sacrifice to Chaos to ascend as a Chaos God.

** The purge of rebels' homeworlds still happens (this time, specifically by Word Bearers), as Imperium's reaction to Horus' rebellion, before the Heresy even ends. In particular, they destroys Chthonia, homeworld of Horus.
** [[BigBookOfWar Codex Astartes]] analogue still gets written -- by Magnus; it's called Codex Secundus.
** Breaking the original Legions into Chapters still happens, albeit those Chapters are larger than in canon (ten thousands marines in each, instead of one thousand). In particular, Blood Ravens and Grey Knights are explicitly successor Chapters of the Thousand Sons.
* ItsAllMyFault: Vulkan blamed himself for his "weakness" due to doing "too little" to save the populace of Terra, and eventually disappeared to the places unknown after the Heresy.

* KillTheOnesYouLove: It's told that slaying Sanguinius (turned Daemon-Prince of Khorne) broke Horus' heart. He whispers "forgive me" while doing this.
* LeeroyJenkins: Vulkan has to be persuaded to not rush to Terra to save its populace right now, before rebels gets ready to siege it.

** No one knows what has happened to Alpha Legion after Second Black Crusade; it's presumed that it was wiped out by either Ultramarines or Word Bearers, and Alpharius is presumed to be killed by Guilliman, but as with anything that has to do with Alpha Legion, the truth is uncertain. Abaddon still refers to finding ''twins'', plural, meaning that he didn't lose hope, and the legends about indigo-plated marines who appears in the time of need [[TheCavalry to help Imperials]] are persistent.
** Perturabo vanished during Sixth Black Crusades, believed to be killed by Rogal Dorn (by then, already a Daemon Prince). But no one knows for sure what has happened to him (or Dorn, for that matter).

* ProHumanTranshuman: The Salamanders sides with Horus, remaining protectors of Humanity first and foremost. During Siege of Terra, they specifically dedicates themselves to protecting civilians from rampaging Emperor's Children, which costs them ''enormous'' casualties. Nowadays, they're often called "Angels of Mercy".

*** Leman Russ vanished after Cleansing of Fenris; this was the last straw for Space Wolves, who have fractured afterwards.

*** Konrad Curze has leaved to the places unknown after the Heresy.
*** Angron leaved to the Eye of Terror, to hunt down fallen Primarchs.
*** At some point after the Heresy, Vulkan had disappeared; Abaddon mentions that people are still searching for him.
*** Alpharius and/or Omegon (one of them [[NeverFoundTheBody was or wasn't killed]] by Guilliman) have disappeared after the Second Black Crusade; Abaddon still believes that they're alive and need to be found.
* RapePillageAndBurn: Emperor's Children have degenerated into hedonism, only leaving the Eye of Terror in seek of slaves or just the blood to spill, for their sick pleasure.
* RoaringRampageOfRevenge: The major motivation for Blood Angels' attacks is to avenge Sanguinius, their Primarch who was killed by Horus.
* RoleSwapAU: It's not just the Heresy being done by different Primarchs; the Emperor himself turns evil, so Horus (who never goes evil) has to pull a rebellion to stop him. As result, the key events like Dropsite Massacre and Siege of Terra are portrayed positively, rather than as atrocities. Additionally, it's Lion El'Johnson who stays on Caliban, and Luther who attacks him, with Luther coming as a victor.
* SealedEvilInACan: Guilliman gets mortally wounded by Angron, and put into stasis.
* ShockingDefeatLegacy: Death of Mortarion deeply affected the Death Guard, leaving a "curse" on their entire Legion, though details aren't explained.
* SocialDarwinist: Iron Hands "justifies" their murderous campaigns as "purging those too weak to live".

* TheStarscream: Heavily {{implied|trope}} with Guilliman, who doesn't bother with assisting the Emperor during the Heresy, awaiting for results of Siege of Terra and who would come out on top, while dedicating this time to reinforcing his own empire. After the Heresy, he managed to preserve Ultramar, instead of running away to the Eye of Terror, albeit Guilliman himself got mortally wounded by Angron, and Ultramarines have pledged themselves to... Malal.
* TalkingToTheDead: Years after the Heresy, Abaddon has a habit of talking with coffins installed on Terra -- Horus, Mortarion and Malcador, retelling them what's going on without them. He doesn't know why he's doing so, but feels that he has to.

* TokenEvilTeammate: Angron and World Eaters are mostly the same as their canon pre-Heresy counterparts. They only ditched their berserker ways after seeing what they can become in Blood Angels, who turned to Khorne.

** No one knows what has happened to Leman Russ after Purging of Fenris; he just vanished..
** No mention of what has happened to Lion's half of Dark Angels after the battle for Caliban and the planet's destruction by Lion.
* WhatHappenedToTheMouse: No mention of Fulgrim's or Ferrus Manus' fate during or after the Heresy.
* WingedHumanoid: Raven Guard aligned with Tzeentch, which resulted in them growing actual wings (and, knowing their patron deity's speciality in wild mutations, likely the other raven-like features).

** Abaddon gets forced to take over as new leader of Imperium after defeat of the Emperor. He eventually stepped down due to old age.

** Unlike canon, here, Grey Knights are Successor Chapter for Thousands Sons. While they're indeed related to Thousands Sons in canon (as a former member of the Legion became the key figure in creating the Grey Knights), they never were a Successor Chapter to any Legion.
** Several canon Successor Chapters still gets created, but with other Primarch as their progenitor.
*** Nova Legion and Star Phantoms both were created from gene-seed of Sons of Horus, instead of Ultramarines and Dark Angels, respectively.
*** Doom Legion and Silver Skulls (both from Ultramarines) are now related to Death Guard.
*** In canon, Blood Ravens don't know their Primarch, though there're many hints towards Thousands Sons. Here, they are explicitly Thousands Sons' Successor Chapter.
*** Mortifactors are Death Eaters' Successor Chapter instead of Ultramarines'.

** Most original loyalists remains loyal to the Emperor (now, they're called "imperialists"), and thus, becomes evil and corrupt. The only exception is Vulkan, who's too pro-human to stay with someone who uses them as [[HumanSacrifice sacrifice to Chaos]], so he sides with ([[AdaptationalHeroism now-good]]) Horus instead.

* AdaptationalHeroism: Horus' rebellion still happens, but this time, it happens because it's Horus who tries to stop his father who went evil. Most original rebels becomes (relatively) good, with exceptions of Lorgar (who's still a prophet of Chaos) and Fulgrim (who's still a Slaanesh worshipper), both of which now sides with Emperor. Luther and his followers are also now explicitly defecting ''from'' bad guys, not the other way around.

* ArchEnemy: Raven Guard (who became Tzeentch worshippers on their own initiative) are now mortal enemies with Night Lords, and frequently clashes with them.

** No one knows what has happened to Alpha Legion after Second Black Crusade; it's presumed that it was wiped out by either Ultramarines or Word Bearers, and Alpharius is presumed to be killed by Guilliman, but as with anything that has to do with Alpha Legion, the truth is uncertain. Abaddon still refers to finding ''twins'', plural, meaning that he didn't lose hope, and the legends about indigo-plated marines who appears in time of need [[TheCavalry to help Imperials]] are persistent.

* TheStarscream: Heavily {{implied|trope}} with Guilliman, who doesn't bother with assisting the Emperor during the Heresy, awaiting for results of Siege of Terra and who would come out on top, while dedicating this time to reinforce his own empire. After the Heresy, he managed to preserve Ultramar, instead of running away to the Eye of Terror, albeit Guilliman himself got mortally wounded by Angron, and Ultramarines have pledged themselves to... Malal.

** Most original loyalists remains loyal to the Emperor (now, they're called "imperialists"), and thus, becomes evil and corrupted. The only exception is Vulkan, who's too pro-human to stay with someone who uses them as [[HumanSacrifice sacrifice to Chaos]], so he sides with ([[AdaptationalHeroism now-good Horus]] instead.

** Some elements of imperialists Legions chose to turn loyalists. In particular, Space Wolves had enough of such turncoats to even make a successor Chapter, Solar Wolves, led by Bjorn the Purehanded. It had since vanished, however, and their fait is unknown.

* KilledOffForReal: Sanguinius is the only Chaos Primarch confirmed to be dead; he didn't return even after Heresy, and his own legion believes that he's dead, and seeks to avenge him.
* KillTheOnesYouLove: It's told that slaying Sanguinius (turned Dameon-Prince of Khorne) broke Horus' heart. He whispers "forgive me" while doing this.

*** Angron leaves to the Eye of Terror, to hunt down fallen Primarchs.

* TheStarscream: Heavily {{implied|trope}} with Guilliman, who doesn't bother with assisting the Emperor during the Heresy, awaiting for results of Siege of Terra and who would come out on top, while dedicating this time to reinforce his own empire. After the Heresy, he managed to preserve Ultramar, instead of running away to the Eye of Chaos, albeit Guilliman himself got mortally wounded by Angron, and Ultramarines have pledged themselves to... Malal.