I have dallied on writing fan fiction for both Warhammer settings. Anyone who has observed the recent kerfuffle should by now know my dissatisfaction with how the Horus Heresy is written and incorporated into the 40k mythos. Particularly is i find that conversations about the era is stagnated around the ubermänchen that the officially endorsed canon permits to dominate the stories set there. If i do end up posting fan fiction in the future then i think it pertinent to put up my own interpretation for anyone jumping in to consult.
So here is a list of the assumptions I thought to put out there if you stumble onto something i write, starting with the key out of story philosophy i run by:
1. The Imperium is wrong, no debate.
There is an irritating trend in 40k discussion where anyone who protests the Imperiums necessity is almost always answered to the tune of "it totally is" or "yes it is terrible, but you must understand, there is no better option". Both do not seem to understand that the "canon" they like to break out like an obnoxious bible thumper is already a largely incoherent mess of kludged together work by many different writers, all with different ideas on how basic concepts of the setting work. Any material supporting the Imperiums necessity therefore have about as much strength as back flipping terminators.
I therefore, as someone with free will and a dislike of the premise, completely reject that assumption and any arguments in favour of it. Before the rise of the Imperium, there were societies better able to resist Chaos and hostile aliens without resorting to atrocity, there existed aliens perfectly willing to coexist peacefully with humanity. And the Emperor ruined all that. If one of the themes of the setting is that the Imperium is a terrible polity to live under, then it should be emphasised that it did not need to exist in the first place.
That will extend to psykers as well. They are not inevitable ticking time bombs, one can live their whole life not knowing they are one, or knowing but choosing not to act on them for fear of social consequences. Before you say it, they are not by default beacons for demons. For the ruinous powers to find a psyker they need to actively be called to them by either the psyker themselves reaching out or cultists using a ritual.
With that out of the way, certain significant setting details will be altered as well. Particularly regarding the Imperiums founding, the Horus Heresy and how Chaos works. I don't have as much to say on the other factions, that might change latter, but I want to focus on what I have fully formed. Beginning with the Great Crusade:
1. The Emperor was not "perpetual" or whatever it is called now.
He was a guy born on Terra lived his pre-rulership days fighting for one of the warlords as a soldier, and later, a prominent commander. His ambition grew gradually after pushed out from Terra and the Sol system, gaining confidence and being egged on by those under him to claim all of humanity. Why did imperial institutions have a poor start with bad foundations leading to the Heresy? The guy in charge was a conqueror before all else. All the science stuff was by the brightest minds he collected like Pokemon.
2. Primarchs were not ubermänchen.
As the Emperor is not a super scientist, where does that leave his sons? The answer is that they are Not his sons. They were born on the worlds where they were found. Neither were they promoted to head of their respective legions once found, they took the long way via centuries long service and acclaim amounts legionnaires recruited from their home worlds. They are not unimportant or unskilled at all, but their overall strength at their height would measure at about above that of a 41st millennium Chapter Master due to better technology, with higher skill at the things they were known for.
So how does Chaos play into this? Well I think the problem with the Ruinous Powers as written is that they are to monolithic. If Chaos is supposed to be true to its namesake then why is the depictions of its influence so stale. Each of the four only have one type of Greater Demon, one type of Lesser Demon and two kinds of war beast, one which is mounted by demons or mortal champions.
The reason for this is the table top game, where the confines of selling figures and keeping a concise army list natural constrains the variety in the game. Not inherently objectionable. So why does the fiction outside the game feel the need to be constrained by those limitations.
1. Chaos demons are legion.
The types of demons you are familiar with are simply the best known to mortals. In reality there are potentially countless different types of demons, sometimes overlapping with others in the warp. When demonic armies are summoned onto the material plane they may include those you are familiar with, mixed in with a cacophonous, colourful riot of the different varieties of creatures. If the warp is suposed to be a space with no hard and fast rules then the entities serve the Dark Powers should display a far greater variety that the tabletop allowed in the written fiction.
2. Borders are non-material and fickle things.
If the Warp is to be a place where tha laws that hold real-space together are mere suggestions, then shouldn't an already illusionary human concept such as borders. So why should there only be demons of a single Ruinous Power. A demon types alignment should generally be on a gradient between the Big Four, with some being easier for a casual observer to place on the spectrum than others. That should enable a more nuanced variety of demons and make room for Chaos Undivided types, after all those kinds of Demon Princes have to go somewhere. Likewise on the border territory between the Big Four there also exists demons that represent amalgamations between the powers contesting the area. Their mixed nature and shaky allegiance makes them loose canons to demons from the core territories, but still useful to keep onside, for however long it lasts.
This also means that the distinction between Greater and Lesser Demons is rarely a clear cut thing. A demons influence can not always be measured by the size of their form in the physical realm. That human sized suit of crimson animated armor might just be one of the most respected smiths from the Slayer Forge, who is bowed to by even Khorne's Heralds and smaller Bloodthirsters. It's a toss up weather a first impression is correct, especially anything that has some Tzeench in it.
3. The Big Four are not the real masterminds, sort of.
This might be a bit tricky to explain. The entities known as Khorne, Slaneesh, Nurgle and Tzeench are not really the ones in charge of the show. They are more like geographical features, built from the base emption that provide their core. Think of them like Azathoth of Lovecraft lore, large blind idiots who's existence regardless effects the universe around them.
The true movers and shakers of the Ruinous Powers are the demons that generally occupy the step above the Greater Demons. There is no single name for this category of demons, variously known as Eidolons, Grand Princes, Supreme Demons and others, these are the most powerful beings that are capable of fully sentient thought and awareness to interact with the Materium. These are the leaders of each of the four "factions" as any mortal knowledgeable enough may know them, with those not fully aligned with one reigning in the border territories between the four.
Any gifts granted that are attributed to one of the four was most likely given by one of the Grand Princes. Gifts of Chaos and other phenomena that benefit the mortal followers of Chaos are caused by individual or multiple demons working in concert. Most mortal followers are unaware of the internal workings of the Realm of Chaos, the theology of the four gods is essentially simplification to quickly explain Chaos to mortals and a convenient fiction to make Chaos appear more omniscient then it really is. It is also an expedient fiction for the Arch-Fiends of the four to spin. Even in hell you can't escape politics.
The problem of canons Chaos Gods is that one of the main threats of the setting are four one dimensional super beings, which fail to be interesting on their own or individually as they frequently dominate plots when handled poorly. Likewise having to constantly resort to capriciousness to resolve the question to why the forces of chaos often seem to self-sabotage becomes worn out quickly.
The way Chaos works here is largely lifted from
this post by Ganonso, who has also done other interesting wold building of the divine side of things for their Warhammer quests.
The final big alterations are ones that have hefty consequences for the 41st millennium:
1. Sorry Jim, the Primarchs are dead.
As far as I am concerned that Primarchs served their narrative purpose after the Heresy's immediate aftermath. The ones who canonically became Demon Princes have noting really narratively to do, and mostly did not seem to really deserve their Demonhod, being how arduous it is supposed to be to obtain. Likewise for those that would disappear wandering into the void, makes for good mythology that their Chapters to tell over the course of millennia, but best left as stories. They to died long ago. The Imperium of the present can not depend on old legends of the past to save them, not can the Arch-Enemy rely on its early champions to drive its forces to its final victory.
2. Abbadon died in one of the early Black Crusades.
I hear that he has been better written recently, but I don't like that for all of 10,000 years only one person is allowed to lead 13 Black Crusades. Why make it the same guy over and over again when you can have multiple diffrent individuals leading the diffrent Crusades. One of the supposed tenets of Chaos worship is that those most capable make it to the top. That would mean that the position of Warmaster should be up for grabs to whoever can convince most the forces in the Eye of Terror to back them, most importantly the Traitor Legions and the big demons in the warp.
It could to possibles such as a magos of the Dark Mechanicus taking the reigns, leading to a Crusade that is particularly targeted toward the loyalist Mechanicus. It could be highly successful Chaos Reaver who leads the Crusade more as if it was a large plunder expedition. With multible types of Warmaster it can make each Crusade have its own character, it's overal goals and execution differing according to each Warmaster motivation and personality. It would also lead to tales of politicking, of both the diplomatic and violent kind leading up to a Crusades launch. It can also mean wacky shenanigans such as major contingents disapproving of a winning candidate, but without sufficient power to contest the choice resort to to boycotting the Black Crusade, starting their own not-Black Crusade in protest.
Conceiving of this has been inspired by open-scetch's quest
Suffer Not. Thought I have regretfully negligent in reading for a while, it is and excellent read with great world building for the setting. The parts where Space Marines get focus are ones that I will take inspiration from in writing them outside of combat.