The gods of Chaos are pretty much just lamer versions of Cthulhu mythos gods, they are evil but some of them represent cool shit blah blah. I mean really there are no good goys here, everyone wants to murderfuck everyone
pretty much Even Slaanesh is just Shub Niggurath but less powerful tho Tzeentch and Yog Sothoth both share lots of traits and messages too. Only thing is Yog Sothoth has a few leg ups in the sense that he represents existence both materiel and immaterial so in a weird way everything is a tiny shard of him. Or maybe Tzeentch is a really really big shard of him and we just don't know it. lol idk man. but like I was saying there are no good guys in 40k, everyone are a buncha assholes but at least Chaos is having fun whilst being an asshole, maybe not as much as orks but still
Conventional views of good and evil don't really have a place in the 40k universe, every faction is a shade of dark grey, except Dark Eldar who are just flat out evil. Chaos Space Marines are simply realists, they see the warp for what it is more or less, an inescapable and all encompassing entity that you must deal with. They've chosen to face it head on, whether that be serving it, harnessing its power for their own ends, or simply looking at it honestly. They've refused the Emperor's grand deception and thus are now free to pursue their goals however they see fit. Many of them are essentially nihilists, having been disillusioned with their prior cause they don't see a greater meaning or cause to fight for, so instead they fight for themselves, their ambitions, their goals, their beliefs. I would however argue that the brutality in which they pursue these often selfish ends is not markedly different than the ways in which they pursued the Emperor's goals prior to their fall, this is important because in 40k the closest gauge for good and evil is by comparison, that and what is most important to you. For Chaos, it's anarchic nature means that it represents absolute freedom, provided you are strong enough, and truth. It's just that the truth happens to be horrific and in order to maintain your freedom you'll often need to commit horrible acts of extreme violence. As for Chaos as an entity itself, well it certainly has a strong tinge of malevolence. However, it more over simply is. The warp is what sentient beings have made it, as it is a reflection of actions and emotions magnified over millennia. However there also seems to be streaks of more noble traits here and there, mostly alluded to. In one of the only stories where the Chaos Gods spoke it was to hold a Chaos Space Marine to his oath to them. He promised to hunt the progeny of an Imperial Fist he believed betrayed him for all time, after his thirst for vengeance was long sated he whished to end the cycle, but the gods showed him the price of forsaking his word was to be spawndom. This shows a sense of cruel justice. In the Ahriman series Tzeentch made a decree, that after Ahriman completed his goal of restoring his Legion he was to be destroyed. Once again this seems to be a malevolent act, unless you look closely at the plot and motivations. For one, Ahriman has committed many evils in the pursuit of his goals, of arguable necessity of course, and they seem to weigh heavily upon him, so there would be a bit of justice in this. Additionally, he doesn't want to be a pawn of Tzeentch's schemes, he rebels against his fate, despises the path it put him on. Though it is to be done in a way that I doubt he'd truly appreciate, this is the reward he wants, to be free of Tzeentch, and the only way he'll be free is by being annihilated(even Tzeentch's court was astounded that he'd willingly free a pawn from its strings). And lastly, Ahriman doesn't really have any desires for after he restores his Legion. It's really all that drives him, the prospect of fixing his mistake, after that he doesn't seem to want keep up the fight, so it may be actually what he wants after he succeeds, to be done with it all. As far back as before the Horus Heresy he'd wanted personal peace, as I recall his hope was that after the Crusade he could retire, open a vineyard, and get away from it all. This is of course essentially an impossibility by 40k. Lastly, Chaos isn't an entity like we would understand. It's energy, like fire or a nuclear explosion. Energy isn't intrinsically good or evil, even if it's highly destructive, how it's used is. This energy also happens to be sentient, but it operates on a level alien to biotic life. A daemon doesn't really understand the concept of mortality, when it kills you it's just taking your energy, like a predator eating its prey. Most of us don't say it's evil that the wolf eats the deer because that's just nature, but since in this allegory we are the deer, then it's evil from our perspective. TL : DR Its complicated and 40k doesn't follow conventional views on morality.
I know I might get in trouble for a double post but I couldn't resist that one Despite a strange movement to rehabilitate the Chaos Gods and associate them with positive things, in fact none of them are meant to be good in any way. They are all examples of extreme behaviour and what happens when things go too far. Except for the sometime, on again off again association of Khorne with honour, GW don't mean the Chaos Gods to be the good guys. Khorne, even when honourable, lives for slaughter. By way of example, each one is an archetype of extremes - Slaanesh, for example, isn't a lovey dovey fertility god without whom there would be no sex. (Sorry TTS, I love you, but no.) Slaanesh is a god of excess and unnatural perversion, things taken to such terrible extremes that they break all bonds of decency and depravity, of lusts that can never truly be slaked, the ultimate escalating fetishist. Tzeentch isn't the god of being a bit creative, he is the arch-politician, the corrupter of every scheme and the one who undermines everything because he doesn't want you to succeed and rise to the top and stay there - Tzeentch has no interest in your continued success, because all he wants is change. Everything is and must continue to be mutable. Etc. None of the Chaos Gods' favours have an off switch. In fact, there are only three ways to end up once you follow the Ruinous Powers - dead, a daemon of some kind (oh, you thought you'd become a Daemon Prince? too bad you're a Nurgling), and as a Chaos Spawn, because Chaos is the gift that keeps on giving. Nurgle is the only one that loves his followers, but since he does it by giving then cancebolaids, that's hardly a plus. Khorne cares not from where the blood flows. Tzeentch and Slaanesh only want to gratify their own desires.
