For those, like me, who are sissies and would like to play Black Crusade and still be the good guys (or at least less evil guys), I've decided to make this. It is based off of 1d4Chan's BrightHammer 40K, tweaked a bit, and unleashed upon the world! There are two ways the following fluff can be used: Either you go the traditional BrightHammer 40K route and make the Lords of Order allies of the Imperium, or you can do a Star Trek mirrorverse thing and make the Imperium evil(er). In any case I'd like to say right off the bat that this sort of thing will change the game play a fair bit; certain talents might need to be altered, certain rules changed a bit. This isn't just a re-fluffing it also changes the mechanics up. I'm doing this as much as a thought experiment as I am making a game mod so I'd appreciate any help or (CONSTRUCTIVE) criticism. In any case, I'll be listing the general differences, then each God. Please feel free to use pieces of this guide or use it wholesale.
In General:
Things are a lot more cordial between the 4 Gods; although they have their disagreements, occasionally violently, they are in general on the same team and are much less at each others throats than their Chaos counterparts.
Human sacrifice, "rap with an e" (censored for some stupid reason), indiscriminate slaughter are right out (the first one is the source of a fair bit of mechanics altering)
Certain mutations might need to be altered
Nurgle in particular is very different (more on that in his entry)
Things are less risky (Daemon weapons are a bit more willing to serve provided their loyalty is earned, for example) the GM might wish to lower the rewards so to speak to compensate.
Going Chaos Spawn is a punishment that is earned, rather than simply failing to "get gud"
The screaming Vortex is less of a hellhole to live in (Q'sal is based on warp power rather than souls, Furia is less "Water World" and more Fenris (harsh, but the people are born survivors and strong) etc.)
Khorne:
Lord of war, battle, rage, bloodshed, conflict, honor, duty, and protection, Khorne's followers are among the greatest warriors in the Galaxy, and value strength above all else. Some would see this as an excuse to slaughter and pillage, and this enrages Khorne, for there is more than mere strength of arms. To Khorne, what matters most is strength of character. Honor, courage, discipline are the highest or virtues. Weakness of arm can be overlooked. Cowardice, treachery or abuse of ones strength cannot. So as much as he and his followers may belittle the weak and helpless, they find themselves firmly planted in their defense. Khorne best helps those who help themselves: standing and fighting despite certain death may earn you a burst of strength. Running away will earn you scorn. Selling out your brothers for your own survival or killing the helpless will earn you a smiting. What matters most is that conflict is done, bloodshed and death are secondary. Not all of Khorne's followers are warriors. Some are athletes, and those who forge arms and armor often give him praise.
Slaanesh:
Lord of perfection, sensation, love, art, and "having a good time", Slaanesh can be a fickle God, but also an enjoyable one. Patron of artists, poets, perfectionists, lovers, gourmets, and those who seek to enjoy all life has to over, his/her followers can seem.... strange to those unfamiliar with them; They enjoy taking things to new levels, broadening their horizons and trying ever newer and wilder delights, although keeping things consensual is a hard and fast rule to be sure. Surprisingly, Slaanesh is often disliked by nobility and rulers for one simple reason: the most common of tenants of Slaanesh is "the more the merrier". To Slaanesh, pleasure, perfection and enjoyment are the rights of everyone, and denying others these things (or having pleasure at the expense of another's suffering) as nobility are wont to do is anathema to Slaanesh. In this way it is surprisingly common for his/her followers to take part in or even start revolts and uprisings if they feel the local rulers are being too "exclusive" or "restrictive". Some may laugh at the thought of the followers of a pleasure God fighting, but they rarely do so more than once; perfection in all things is their goal, and that includes combat skills. Slaanesh includes a large number of duelists among his/her number, and they are often quite good at speaking for the masses and being leaders of men.
Tzeentch:
Lord of knowledge, plans, magic, schemes, freedom, hope and change, Tzeentch is often an inscrutable God, his followers mysterious and hidden. Tzeentch is venerated by magi, scholars, revolutionaries, philosophers and inventors. They seek to create new things, discover and create, seek out and discover knowledge and lore, and further the strength of the arcane. Master plotters, they are among the greatest strategists and schemers alive, and the most powerful of psykers. They delight in shaking up old traditions and in bringing change and hope to the oppressed; Tzeentch's nature as a God of change and hope makes him a natural revolutionary. Oddly enough for a God of plots and schemes, Tzeentch is not the God of fate. Indeed, he is opposed to the very idea; as a God of freedom and evolution, the idea of everything following a scripted part is anathema to him, and those who seek to bind others in chains find themselves wrapped in chains of their own, made of the endless plots of their downfall.
Nurgle:
Lord of Nature, stability, health, life, and also of death, disease, decay, and rebirth, Nurgle is the God of duality. On one hand he is the god of nature, of the forest, of growth and life, but he with every summer must come a winter, with every birth must come a death, and every beginning has an end. Of course, every end also has a new beginning. Nurgle is venerated by those who work with nature, who seek to build things that last and endure. Construction workers, farmers, average citizens and law makers often pay him homage. Nurgle teaches that life is precious and fleeting, but ultimately worth living, and to enjoy what time you have. Jovial and kind, he is a caring God, but when the time comes he and his daemons take on the aspects of decay, disease, death and entropy, becoming grim and dispassionate as they do what must be done. In the end they become far more energized than before, taking on the aspect of rebirth as new life springs from the old. Birth, life, decay, death, rebirth. The cycle of life and all in entails, including permanence, fortitude and endurance are his dealings. Those who seek to upset this balance, to defile nature, and to make life not worth living find themselves facing an enemy who can endure anything they throw at it while slowly wearing them down and bringing them to heal.
Daemons
Khorne's daemons often have less of a "wild" look about them, being more humanoid, more armored and dignified. Tzeentch's Lords of Change have the aspects of hawks, eagles or owls, and his lesser daemons are more intelligent. Nurgle's daemons appear based on plant life or healthy animals/beings, taking on aspects of rot and decay (as they are in regular 40K) or of the more abstract entropy as needed. Daemons of Slaanesh are largely unchanged, albeit a bit more clothed.
Relationships between the Gods
Khorne is often venerated alongside Nurgle by survivalists, seeking from the latter the strength to endure and from the former the strength to overpower. He and Slaanesh find common ground in the perfection of swordplay, and with Tzeentch in the art of strategy and moral philosophy. Nurgle is venerated alongside Slaanesh at feasts and the like, praising the latter for the extravagant preparation and the former for the crops to make it and the sustenance it provides. He and Tzeentch are seen as the pillars of civilization, the former providing the bedrock of it and permanence and the latter its evolution into greater forms, with Khorne proving the means of protection/expansion with Slaanesh providing what makes it worthwhile. Tzeentch and Nurgle also play off each other, Tzeentch preventing Nurgle from getting bogged down or decaying too soon, and Nurgle slowing Tzeentch down enough that he can enjoy what he has and think before moving on to change it.
All for now, will edit later. Please give thoughts, feed back and suggestion and praise, but take any trolling elsewhere.
Edited by InquistiorCalinx