"Just." Such a strange word, an alien one to a true devotee of chaos.... Perhaps, Warmaster Horus and his brothers had been "just" at one point, though once you delve into chaos, your true goal blurs and warps, just like any who are tainted by it's magnificent touch.

The hole that Magnus tore (albeit accidentally) in the new section of the Webway that the Emperor was using the Golden Throne to construct never actually closed. The Emperor was only able to leave the Imperial Dungeon to fight Horus because he had the second strongest psyker mankind had ever produced at hand. By the time the Emperor got back from his little trip to Horus' flagship, the strain of holding the hole in the Webway closed had killed Malcador. That is why the Emperor needed to be interred on the Golden Throne.

If some massively powerful psyker hadn't jumped on the Golden Throne immediately, daemons would have had permanent access to Terra directly from the Warp. Magnus probably would have done the trick if he'd been on Terra at the time, but any other psyker would be at best just a temporary solution.

I do know that and I thought about that, but between him being mortally wounded and getting to the golden throne took some time probably, or at least we don´t know how he got back, just that Dorn took him back. More than enough time to come back if being a perpetual. That´s why I don´t agree with you and I still don´t think he is a perpetual. Don´t start that it was simply timed perfectly

But we are drifting off topic here...

Magnus was on Terra during the fight, but not on the loyalist side anymore. Has something to do with, heck I don't know, some wolf-dick burning his home on behalf of the Emperor of Douche-kind because he tried to warn him that any of this would happen.

Dorn was supposed to have been with the Emperor, they just got separated during the fighting. Even if it took Dorn another ten minutes to reach the Emperor after the fight ended, they teleported directly back to the Throne. That's long enough for daemons to enter Terra, but not really enough for a perpetual to regenerate from catastrophic full body injuries.

It'd be weird and random if Vulcan were the only one of the primarch's to have an ability that the Emperor didn't share.

Again, impeccable timing then. Furthermore, perpetuals can "come back" quite quickly see John Grammaticus in The Unremembered Empire/Vulkan Lives. And a being like the Emperor is not as quick as a "lowly" perpetual? That rather proves that he isn´t a perpetual.

The whole issue with Vulcan being a perpetual is weird and one of the biggest WTF moments in my long history of reading 40k novels...

All in all I fear that GW is steering in that direction and establishing him as a perpetual. So further down the road, proof may come that he is actually one. Geez, even Lexicanum lists him as one

It seems to me that many were justified to a point. While the Emperor might have shown them motivation, it was the legions themselves who ultimately chose damnation/enlightenment/whatever-you-wish-to-name it. While the Emperor's treatment of Lorgar was certainly was drove him to following a very different path, it was Lorgar himself who sought out the dark gods and opted to follow what the considered to be their truth. In Perturabo's case he certainly had motivation and reasons for turning upon the Emperor, not those people commonly think, but it was the choice of the Iron Warriors to truly fall to Chaos rather than merely be traitors.
The same ultimately goes with Angron, with the Emperor pulling a perplexity daft act which would forever turn him into a loose cannon at best. Then never took the steps to prevent he and his legion easily falling to Khorne without devotion and faith to balance their bloodlust; or forcibly shut down and prevent further creation of the Nails.

Some had reasoning for turning upon the Emperor, but total justification? How justified can rebellion be when you're listening to the whispers of a daemon.

not every legion rebelled because of deamons ,death guard for example had a really good reason to rebel

You mentioned some cases yourself where daemons were not involved in the process. The same goes for Magnus who was forced to change sides because his attempt to warn the Emperor was met with violence, which surely goes hand in hand with what happened due to this attempt, but he tried to save the Imperium and was attacked in return. And somehow joining the only other side instead of fighting against the whole universe with no safe place was not appealing to any of them.


Also, somehow it sounds like you believe that rebellion cannot be just if there are daemons involved. Every reason someone had for rebellion is valid on it's own, no matter the involvement of daemons.

I've read both reasons, those from the old lore and the new novels, and i'm sorry but neither one was truly justified. Mortarion's dented pride and being on better terms with Horus pale in comparison to some of the others, and his new goal of a universe without psykers was by someone who apparently did not fully understand what he was fighting. In fact, the book which brings this up points out that, if anything, he only made things far worse in this regard with countless sorcerers and Chaos infused worshipers rising up.

Except that Magnus did listen to daemons and brokered deals with this personally long before any of that happened. In an effort to save his legion from genetic degeneration he made a deal with Tzeentch himself and ultimately became his plaything. Perhaps his motivations might have been right but he was being manipulated by others, and seemed to understand to a degree that he was damned a long time ago.

Well, having just reasons for a rebellion tends to be a little difficult when half your information comes from millennia old beings formed of extreme hatred, bloodlust, ecstasy or a warped perversion of hope. Especially when they have the nasty habit of only telling the truth when no one will believe them. Ultimately nearly everything here does come back to them. Lorgar listened to one, as did Kor Phaeron, both of who were instrumental in creating the heresy. The same goes with Horus, either through the information shown by Erebus or something in his guise if what later books suggest is true.

Again, many of them had reasoning for turning on the Emperor, and understandable motivations, but i'm not sure if they could be deemed truly justifiable given the methods they utilised.