That Emperor Guy, what was his deal...

[Prathios]

Ok, so there is very little material available on the Emperor and as such he remains a very ambiguous and mysterious figure in the Warhammer universe. But there is enough out there now that I think a great deal can be pieced together about him and his motives. So here is what I have. Oh and please correct any mistakes I might have made and I'd love to hear your opinions on this.

 

About 38,000 years before the Horus Heresy a collection of Shaman from various cultures gathered together and bound their souls into a single entity. Some reports say this was a mass suicide but besides the next part most of this is at best speculation. Result is that the Emperor is born in Anatolia (Turkey) about 3000 years before the pyramids are built. Almost from his birth he dedicates his life to the singular goal of defeating the powers of Chaos due to the nature of their relationship with mankind and human souls.

 

Not much is mentioned about the Emperor's role in the early stages of the human race but he is supposed to have guided humanity from behind the scenes to some degree. But he is mentioned about the middle ages in Libya to have defeated the C'tan god the void dragon as it was recovering from its sleep. How he was to perform the next step is not elaborated on but needless to say he took its carcass and entombed it on mars and set forth the process that would lead to the Mechanicum worshiping a figure they would call the Omnisiah.

 

The Emperor was in fact a very capable farseer who likely could read the future better than the Eldar despite what they might say, mostly due to their arrogance and fear of what they do not understand. Not to tangent to much but an objective look at his actions versus the abilities of a farseer will reveal this. His lack of foresight on the HH is a direct result of the interference of the Chaos gods on his ability to read the future. The four of them actually went out of their way to stir the warp up to block his vision of the Heresy. So it bears repeating that all four of the great powers went out of their way to block the foresight of a single individual.

 

I brought this last part up because the Emperor foresaw the coming of the Old Night and engineered the creation of the Standard Template Construct so that too much technology would not be lost. This is also the reason why he did not choose to rise to power at this time but rather wait until its all over.

 

So once warp travel was capable again the Emperor started his conquest of Terra with his Custodes Guard who were the first Space Marines that even the primarchs were based upon. (though at this time they were not referred to as Custodes Guard.) It was also in this time he put forth the idea of the Imperial Truth which is a bit of a riddle. Here is my take though. In order to better prepare mankind to deal with the powers of the warp the Emperor decided to hide them from humanity. To keep their very existence a secret as best he could, and as such he set forth the Imperial Truth with the hopes that mankind would explain away warp related activity through logical scientific means. By this point in his life it would be difficult for the Emperor not to understand what he himself was so denying his own godhood was likely one more link in his chain to deny the forces of chaos. Though ironically the Emperor fully embraced godhood with his creating the prophecy of his return to Mars as the Omnisiah.

(A note on the story "the last church" from Tales of Heresy, the fresco on the ceiling of the church shows a silver dragon fighting a golden knight... which is very obviously the Void Dragon fighting the Emperor.)

 

 

The Emperor also was well aware of mankinds self destructive behavior which was why he did not unlock all the tech vaults on Terra and Mars. He understood the danger in advanced AI and some of the other more destructive human technology. This is why the fabricator general of Mars fell to chaos, because he did not understand why the Emperor was doing the things he did (a reoccurring theme to be sure.)

 

After the creation of the Primarchs and the start of the great crusade things get truly interesting. After fighting with his legions and recovering his lost sons the Emperor retired to his vaults on Terra and began work on the human webway. This of course would have been his ultimate triumph over the powers of Chaos as it would have removed humanities requirement to use the warp to travel between stars. However several of his policies began to backfire at this point and though a great figure he made some mistakes. He failed to prepare his primarchs to deal with Chaos and did not reveal its true nature to them fully. As such Horus was not prepared to fight against them when they targeted his soul. He also was clearly exhibiting certain aspects of his own divine nature at this time with people in the crusade able to tap into his spirit to fight the powers of the warp and perform "miracles." But again he took the approach that ignorance was the best method for dealing with the ruinous powers.

 

It was perhaps around this time he realized that the heresy was going to take place or at least he had some idea of a civil war. Else there would have been no reason for his sudden fortification of Terra. He still felt that his webway which was almost complete took priority over dealing with the civil war. Then Magnus due to his ignorance of the Emperors work cast a spell to warn him of Horus that shattered his webway portal momentarily and allowed the powers of the warp to invade the tunnel the Emperor had created with his mind from the eldar webway to Terra. This in the end was why Malcador was required to use the golden throne in the Emperors place.

 

Well during the conflict when the Emperor finally did engage Horus in battle aboard his flagship some have argued as to why he did not kill horus sooner but it was in his nature. The Emperor had acted in a fatherly manner for 50,000 years over the human race and Horus was the closest thing to a son he had ever allowed himself to have. He wanted desperately for Horus to be savable. Despite this when Horus flayed the Imperial Fist terminator alive with a glance the Emperor resolved himself to end it and destroyed the champion of the chaos gods with a single thought, erasing his soul entirely from the warp. But at this point he was already too wounded to survive without aid. Had Magnus not breached the webway the golden throne would have revived the Emperor to full but because his will was required to keep the daemons at bay the throne would simply prolong his suffering. But he was willing to do this to save mankind.

 

So my impressions after having read pretty well everything regarding the Emperor is this; he was a very noble individual who constantly gave of himself to ensure mankind's survival. He had all the flaws and talents that made up mankind and used them all to walk the thin line required between compassion and unforgiving violence to ensure mankind could survive in the galaxy. In mechanicum it reveals to what lengths the Emperor went and how difficult it was to keep humanity from falling off into the void. His single greatest flaw could have been the Imperial Truth. Mankind's misunderstanding the warp led to its downfall to it. Horus would likely have laughed in their faces had he truly known what he was dealing with. Not even Magnus knew what the ruinous powers were or were capable of.

 

Due to the manner of his creation and the powers he wielded he was almost without a doubt a god. The ability of other people even non-psycher's to channel his power is a pretty solid hint that his divinity was no mistake. Had Magnus not played with the warp (and again by proxy had the Emperor explained the warp to Magnus) the powers of Chaos would likely have been destroyed by the 41st millennium and a golden age would reign. But hey, that's no fun right?

 

So now the only question left is, will he ascend to true godhood when he dies or be reborn? Or perhaps simply die?

 

Well what do you think?

 

 

*edited to correct birthplace and dates* Thank you Tyrak, Anaraxes, and Sons of Horus.

[Logain the Ranger]

You defiantly put a lot of time into this. I agree that the Imperial Truth was his down fall. I believe he would only need to inform the Primarchs about the nature of chaos. I beleive had the Emperor done that than I think it would of cut down on the traitor Primarchs. I believe that Lorgar, Angron, and Curze would of still betrayed.

[Prathios]

You defiantly put a lot of time into this. I agree that the Imperial Truth was his down fall. I believe he would only need to inform the Primarchs about the nature of chaos. I beleive had the Emperor done that than I think it would of cut down on the traitor Primarchs. I believe that Lorgar, Angron, and Curze would of still betrayed.

 

Don't forget without the Imperial Truth the Emperor would likely have embraced Lorgar rather than shun him. This would have nipped the whole thing in the bud. Lorgar had good intentions. He was simply manipulated by the ruinous powers.

[Grand Master Tyrak]

Result is that the Emperor is born in Argentina about 15,000 years before the pyramids are built.

 

I think it was Anatolia (Turkey).

[Sons of Horus]

he was born in 8,000 B.C. in Anatolia.

[Castlerook]

Which would put it about 38,000 years before the Heresy, rather the 20,000 years you have noted.

 

And the reason for the Shamen of Earth killing themselves was that they found they couldn't reincarnate as they had done generations beforehand, due to some of the Chaos Gods starting to coalecse (sp?) in the Warp. As they knew that less and less would come back over successive generations, meaning less and less Shamen to guide Humanity, they decided to create one being to help and guide Humanity, and this one individual would have the powers of the Shamen. In order to do this, the Shamen committed mass suicide. One year later, that individual was born.

 

And that little boy grew up to be the Emperor of Mankind :P

 

Just some more info for you.

[Prathios]

Which would put it about 38,000 years before the Heresy, rather the 20,000 years you have noted.

 

And the reason for the Shamen of Earth killing themselves was that they found they couldn't reincarnate as they had done generations beforehand, due to some of the Chaos Gods starting to coalecse (sp?) in the Warp. As they knew that less and less would come back over successive generations, meaning less and less Shamen to guide Humanity, they decided to create one being to help and guide Humanity, and this one individual would have the powers of the Shamen. In order to do this, the Shamen committed mass suicide. One year later, that individual was born.

 

And that little boy grew up to be the Emperor of Mankind :P

 

Just some more info for you.

 

Yeah I knew this but I could do little to verify it. This was from rogue trader was it not? It hasn't been mentioned at all in the current HH books so I thought perhaps best for now to leave it out. Here's to hoping they bring it up at some point.

[Prathios]

accidental post, ignore.

[Brother Captain Andrecus]

Very interesting. :)

 

I agree with your conclusion, and you seem to have most of your facts straight. I hadn't thought about the "human webway" thing before now, though. Very interesting indeed.

[Captain Mike]

Wow.

 

You really have put a lot of thought into this, and scraped the barrel for every last scrap of info. Such a project is worthy of the Emperor himself! The only thing I find odd is that the primarchs knew a little about the warp, and did understand the dangers ( Horus talks to Loken about it in Horus Rising). And so did normal humans, otherwise psykers (who were allowed for a short time, and navigators always) would run contrary to the Imperial truth. I agree, he did rationalise it with science but not complete ignorance.

 

Human webway... that would have been awesome. Eldar appear on a world, go to ravage it only to find humans beam down on them!

[Marshall Riese]

Which would put it about 38,000 years before the Heresy, rather the 20,000 years you have noted.

 

And the reason for the Shamen of Earth killing themselves was that they found they couldn't reincarnate as they had done generations beforehand, due to some of the Chaos Gods starting to coalecse (sp?) in the Warp. As they knew that less and less would come back over successive generations, meaning less and less Shamen to guide Humanity, they decided to create one being to help and guide Humanity, and this one individual would have the powers of the Shamen. In order to do this, the Shamen committed mass suicide. One year later, that individual was born.

 

And that little boy grew up to be the Emperor of Mankind :)

 

Just some more info for you.

 

Yeah I knew this but I could do little to verify it. This was from rogue trader was it not? It hasn't been mentioned at all in the current HH books so I thought perhaps best for now to leave it out. Here's to hoping they bring it up at some point.

 

Not Rogue Trader but from the Realms of Chaos duology. Where it also discusses the Sensei and Starchild.

[yergerjo]

It was perhaps around this time he realized that the heresy was going to take place or at least he had some idea of a civil war. Else there would have been no reason for his sudden fortification of Terra. He still felt that his webway which was almost complete took priority over dealing with the civil war. Then Magnus due to his ignorance of the Emperors work cast a spell to warn him of Horus that shattered his webway portal momentarily and allowed the powers of the warp to invade the tunnel the Emperor had created with his mind from the eldar webway to Terra. This in the end was why Malcador was required to use the golden throne in the Emperors place.

 

It also makes sense that he'd fortify Terra while he was preparing the human Webway in order to guard against a massive Eldar Assault when they realized what he was doing.

 

Not only would his creation of a human webway limit the power of Chaos but would be the death stroke of the Eldar, especially if his linked into theirs...then the Marines could just walk onto every Craftworld and maiden planet and obliterate the Eldar.

[Prathios]

Which would put it about 38,000 years before the Heresy, rather the 20,000 years you have noted.

 

And the reason for the Shamen of Earth killing themselves was that they found they couldn't reincarnate as they had done generations beforehand, due to some of the Chaos Gods starting to coalecse (sp?) in the Warp. As they knew that less and less would come back over successive generations, meaning less and less Shamen to guide Humanity, they decided to create one being to help and guide Humanity, and this one individual would have the powers of the Shamen. In order to do this, the Shamen committed mass suicide. One year later, that individual was born.

 

And that little boy grew up to be the Emperor of Mankind :)

 

Just some more info for you.

 

Yeah I knew this but I could do little to verify it. This was from rogue trader was it not? It hasn't been mentioned at all in the current HH books so I thought perhaps best for now to leave it out. Here's to hoping they bring it up at some point.

 

Not Rogue Trader but from the Realms of Chaos duology. Where it also discusses the Sensei and Starchild.

 

Ah good then I'm actually glad to have skipped it. Thats a whole bag of tricks I'd rather not open. I did find the Sensei a very very strange idea. I also remember several people talked about Sigmar being the Starchild. Either way this stuff is a bit off the wall in some respects and I wouldn't be surprised if it never really gets touched on again. Save perhaps the starchild due to its obviousness.

[Wulfkry]

Well from what ive read thats about as complete a picture of the big E that we got great job on that btw. GW already has already said in 5th ed that the GT is failing so my hopes are him being reborn and trying to fix what his imperium has become.

[Sons of Horus]

if there's one thing i can't agree with, it's the emperor being reborn. he's not a god. he's just 1,000 shamans plus a bit more. he's the most powerful human psyker/warrior ever but in the end he's still just a human.

[lee265]

Personal thoughts is that he is one of the missing primarchs I forget where this comes from but when he walked out of the ship to find i believe it was Fulgrim when he was with mangus his armour had a silver eagle and bronze Emperor Bob wheres gold? Also we know that the primarchs had some of his abilities meaning this one must have got some of his more coolo ones to fight chaos Horus and live, and if your going to say astronomican well apparently Primarchs are like giant Psychic batteries that is why Emperor Bob wanted Leman Russ to get Magnus so its possible that any of them could have done that. Finally also lacks reference but when that one group was permitted enterence to the golden throne they were sworn to secrecy, Why? anyway my theory Goes like this he he is just waiting for certain events to occure and then he steps out of the shadows and leads humanity again possible to a new golden age.

 

Or I'm bored and just into all sorts of crazy conspiracy theories :)

also its not established anatolia is Turky and the custodius is seperate from the marines period they were created seperat.

[_Caesar_]

also its not established anatolia is Turky and the custodius is seperate from the marines period they were created seperat.

 

Anatolia (also called Asia Minor) is the region where Turkey now exists. The name Anatolia originates from the ancient Greek name for the region, Αnatolí.

 

The Custodes were, indeed, created separately from the Emperor's first thunderbolt and lightning clad warriors. Based on what I recall, I believe the Custodes are genetic descendants of the Emperor like the Space Marines are genetic descendants of the Primarchs. I also seem to remember reading something recently about the Space Marines having a more simplified genetic code than the Custodes in order for easier "mass production" for lack of a better term.

 

As far as the Emperor and his intentions, I think it's all a setup. I think he is completely aware of what he has done/is doing/will do and the effects that his actions have on the galaxy. I believe his final card has yet to be played and I think it will take the form of him returning when the Imperium is in the most dire need of a savior. The return of mankind's greatest hero (who is also perceived as a god) will cause an outpouring of faith and devotion from the Imperium as a whole that will empower the Emperor's warp presence and, perhaps, allow him to vanquish the Chaos gods. Or at least bring about an apocalyptic battle between himself and the Chaos gods that will usher the end of the galaxy as we know it, e.g. Ragnarok. The Primarchs will probably all be there too. :P

[Grand Master Tyrak]

Sons of Horus Posted Today, 07:48 AM

if there's one thing i can't agree with, it's the emperor being reborn. he's not a god. he's just 1,000 shamans plus a bit more. he's the most powerful human psyker/warrior ever but in the end he's still just a human.

 

Well, he's not a human, but anyways. Currently there are two theories on the Emperor being reborn. The first is the most common one, that the Emperor will get up off the Golden Throne and be healed again. This is the reason why Russ went off to find the Tree of Life, to try to heal the Emperor. Nothing particularly spooky or godlike in this process, it's just sci-fi medicine.

 

The second, much less widely held theory is that of the Thorians. They believe that the Emperor is already gone and that the body on the Golden Throne is no longer the Emperor. They believe the Emperor has ascended to the warp, and now acts through various avatars, Sebastian Thor being the first. They hope to find an avatar that can be used to sustain the Emperor permanently, and so 'bring him back' that way. This one is the dodgy one, hence why it is much less common. Lots of *ahem* 'interesting' stuff in that theory, and that's the one I think you are referring to, since it involves genuine rebirth.

[Gv0zD]

@ Prathios

 

That's great amount of info about The Emperor. It was an interesting reding. Thanks!

 

Some personal thoughts. If the human webway meant the obvious end of Eldar, it is no wonder why the eldar exarch leading the cabal tried to convince Alpharius to aid Horus in defeating the Emperor.

Regarding Imperial Truth. I think that if the Emperor had revealed the true essence of Chaos to the primarch and the people of the Imperium, there will be still some power-hungry individuals willing to ally with Chaos in order to obtain more power and influence (suchcould be found among ordinary people and among astartes, remeber Typhon). It's just like explaining the harm of cigarettes to children - they might even understand it, but there will be some willing to try it.

Also there were so many cults on former human colonies the Emperor sought to unite, that teaching every colony about the Chaos (its bad influence, proving their dieties to be the Chaos gods) would consume a lot of time during the Great Crusade. It was easier to bring the to compliance with the Imperial truth.

[Prathios]

if there's one thing i can't agree with, it's the emperor being reborn. he's not a god. he's just 1,000 shamans plus a bit more. he's the most powerful human psyker/warrior ever but in the end he's still just a human.

 

I find I disagree with your logic. First what is a god? Not what is God (hence the big G) but a god. Take Thor or any of the ascended Greek pantheon. The Emperor has performed feats and would lie on a higher level of both consciousness and ability than these figures. The Emperor has already proven to be nigh omniscient. He seems to be at least aware of events that occur on the other side of the galaxy from himself without the need of a vox. People can actually call on his essence through prayer, if this doesn't qualify as godlike power nothing does. Thats one of the strange things about the Imperial cult. Until I read a great deal of the BL stuff and most of the codex fluff I wasn't sure what the church really was based on. What good is it to pray to the Emperor. Then I read false gods and it all changed. The Emperor actually does answer some of these prayers and really does come to the aid of his devout. Case in point, Sisters of Battle. Those acts of faith aren't just in their head. Honestly I almost laughed at your comment that "he's just 1,000 shamans plus a bit more." simply because it kinda sounds sarcastic. What makes a human a human? The human soul is a good argument, so what happens when you have over 1000 souls combined in one? You become a god...

 

The Custodes were, indeed, created separately from the Emperor's first thunderbolt and lightning clad warriors. Based on what I recall, I believe the Custodes are genetic descendants of the Emperor like the Space Marines are genetic descendants of the Primarchs. I also seem to remember reading something recently about the Space Marines having a more simplified genetic code than the Custodes in order for easier "mass production" for lack of a better term.

 

This is how I read it, which is why I drew the conclusion that the Custodes (or what was to become them in name) were the original Thunderbolt and Lightning army. Since they were the first creations upon which the emperor said he modified to create the Astartes that would make them the Custodes. I could be missing something but I think this is correct.

 

The second, much less widely held theory is that of the Thorians. They believe that the Emperor is already gone and that the body on the Golden Throne is no longer the Emperor. They believe the Emperor has ascended to the warp, and now acts through various avatars, Sebastian Thor being the first. They hope to find an avatar that can be used to sustain the Emperor permanently, and so 'bring him back' that way. This one is the dodgy one, hence why it is much less common. Lots of *ahem* 'interesting' stuff in that theory, and that's the one I think you are referring to, since it involves genuine rebirth.

 

I always liked the Thorians because I find this theory pretty unique. Heck, it could be true but I sincerely doubt it. I think its taking the last of the Emperors spirit to keep the astronomicon going. That and I think his soul is anchored to his body. However I think currently the most likely theory is he will simply ascend to warp godhood. This of course would be super bad news for the other four. If the Emperor was as powerful as he was on the material plane his spirit as a warp god would likely be able to march right up to Tzeentch and wipe him out.

 

And just imagine what seeing the Emperor becoming a warp god would do to the traitor marines. They would be so confused. I imagine a bunch of them would simply commit suicide at the proof of how wrong they were.

 

Some personal thoughts. If the human webway meant the obvious end of Eldar, it is no wonder why the eldar exarch leading the cabal tried to convince Alpharius to aid Horus in defeating the Emperor.

Regarding Imperial Truth. I think that if the Emperor had revealed the true essence of Chaos to the primarch and the people of the Imperium, there will be still some power-hungry individuals willing to ally with Chaos in order to obtain more power and influence (suchcould be found among ordinary people and among astartes, remeber Typhon). It's just like explaining the harm of cigarettes to children - they might even understand it, but there will be some willing to try it.

Also there were so many cults on former human colonies the Emperor sought to unite, that teaching every colony about the Chaos (its bad influence, proving their dieties to be the Chaos gods) would consume a lot of time during the Great Crusade. It was easier to bring the to compliance with the Imperial truth.

 

Thank you for the kind words. Here is my take on the webway. The Emperor could not make a webway as he lacked the resources and technology so he was making a bridge to allow humans to access the Eldar web. I don't think this would actually mean the end of the Eldar. It would simply mean that they would have to forfeit control of the webway. They could still use it just like the Imperium, they would simply have to stay out of the way. Either way though its not a good thing for the Eldar, just not a game ender either. I think though that the farseers would encourage humanity to use the web if they knew that it would keep them away from the warp. And the Eldar that spoke to Alpharius and Omegon was one of the most unique and interesting turns in the whole heresy so far. I wonder what ever happened to those two...

 

As for the Imperial Truth I think it would have been a huge mistake to inform the general public about the warp. I totally agree that letting the masses in on the secret would have been a huge mistake. But he should have given full disclosure to his primarchs. Not telling Horus about the ruinous powers was the Emperor's downfall after all. Well that or not telling Magnus. One or the other.

[Twin .44]

CAUTION! THIS IS A PERSONAL THEORY! I fully admit I have no facts on what I'm about to say, it's just my interpretation and how I see things in the World of 40K.

 

To me, the Emperor knew what was happening/going to happen with Horus and the others. I see this because when Horus was sent back to see the "incubation chambers" of the Primarchs, the Emperor seemed to let it happen. It was purely necessary. He knew that horus would betray him and he had to kill him. But in the last minute, he just couldn't do it. God or no, Horus was still his "Son" and what good father could do that? So the Golden throne was constructed until GW decided on what to do.

 

NEXT! I also figured that when the Emperor left the Crusade, it was not only to build the Astonomicon, the webway, because of the Eldar, or whatever else. Yes, those were reasons as well, and important ones at that, but he also had to hold of Horus' attack.

 

Like I said, this is how I interpreted it. I'm not trying to harbor any hatred, and like all good stories and literature, there is never a single translation. That's what poetry is for people.

[Sons of Horus]

@ Prathios: it's just my opinion for now while GW isn't releasing anything official about the emperor being a god. and it will stay that way until GW does.

[yergerjo]

Thank you for the kind words. Here is my take on the webway. The Emperor could not make a webway as he lacked the resources and technology so he was making a bridge to allow humans to access the Eldar web. I don't think this would actually mean the end of the Eldar. It would simply mean that they would have to forfeit control of the webway. They could still use it just like the Imperium, they would simply have to stay out of the way. Either way though its not a good thing for the Eldar, just not a game ender either. I think though that the farseers would encourage humanity to use the web if they knew that it would keep them away from the warp. And the Eldar that spoke to Alpharius and Omegon was one of the most unique and interesting turns in the whole heresy so far. I wonder what ever happened to those two...

 

Humans cannot peacefully coexist with any Xenos for any real length of time. There would be no sharing of the webway. We would use sure, but think of all the exits/entrances that the Eldar have, of course we'd use those portals...step through firing bolter rounds everywhere. THEN we'd control the webway.

[Grand Master Tyrak]

Thank you for the kind words. Here is my take on the webway. The Emperor could not make a webway as he lacked the resources and technology so he was making a bridge to allow humans to access the Eldar web. I don't think this would actually mean the end of the Eldar. It would simply mean that they would have to forfeit control of the webway. They could still use it just like the Imperium, they would simply have to stay out of the way. Either way though its not a good thing for the Eldar, just not a game ender either. I think though that the farseers would encourage humanity to use the web if they knew that it would keep them away from the warp. And the Eldar that spoke to Alpharius and Omegon was one of the most unique and interesting turns in the whole heresy so far. I wonder what ever happened to those two...

Humans cannot peacefully coexist with any Xenos for any real length of time. There would be no sharing of the webway. We would use sure, but think of all the exits/entrances that the Eldar have, of course we'd use those portals...step through firing bolter rounds everywhere. THEN we'd control the webway.

 

Er, Eldar still think the galaxy belongs to them. I don't know where this perception of friendly, helpful Eldar has sprung from, but I see it a lot now on the B&C. The Eldar are still out for themselves. They just seem 'friendly' because the Imperium is anti-Chaos (like them) and anti-Xenos (like them, except they hate Humans rather than themselves). So they'll play along, for now. They'll still try to screw us over as soon as it's safe for them to do so.

 

If the Emperor was as powerful as he was on the material plane his spirit as a warp god would likely be able to march right up to Tzeentch and wipe him out.

 

Well, the Emperor did present a serious challenge to the power of the Big Four when he walked among Humanity. I imagine they don't want him becoming that much of a threat again.

Then again, the Emperor is the only thing that has made the Big Four genuinely unite.

[Askari]

The Custodes weren't used to unite Terra. The emperor used primitive versions of the Astartes sort of like the geno-troops from Legion. Then he refined the technology to create stronger marines. I don't believe the fluff ever states who was made first, the primarchs and their marines or the Custodes. The argument on that could go both ways.