I've been reading the Horus Heresy series and I've recently completed both The Thousand Sons and The Master of Mankind. The implication throughout the series (and again in this question) is that each of the Primarchs were created for a reason.

In The Master of Mankind The Emperor explains to Ra that his ultimate goal was to reduce mankind's dependency on the warp by using the webway. With no need of psykers, astropaths, or navigators humanity would be immune to the chaos gods.

It's hinted (again suggested in the linked question) that he planned for the 15th Primarch (Magnus the Red) to sit on the Golden Throne and operate the webway. Obviously that went slightly awry when:

Magnus, after hearing of Horus' betrayal breached the psychic fortifications around the webway in an attempt to contact his "father" and let chaos in.

However this confuses me. If the Emperor ultimately intends for himself and Magnus to be the only remaining psychers then why does he sanction him at Nikea? At this point in the series Magnus had indeed done nothing wrong!

Why was The Emperor was forbidding Magnus to do the very role he was created to do?


If Magnus was intended to be the psychic primarch then why order him and his legion not to use their abilities?

  • If memory serves, the XV, and other Astartes Librarians were a sort of necessary evil to be used during the Great Crusade until the Imperial Dungeon/Webway was complete. After Horus turned, the Emperor realized his mistake and called Nikaea to stop the Librarians. Commented Aug 29, 2018 at 17:14
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    Nikaea was before Horus turned. After the heresy, part of the edict was reversed to permit librarians for fighting chaos.
    – Brian
    Commented Aug 29, 2018 at 21:15
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    At one point in the lore, the Edict of Nikaea banned Sorcery not psychic powers. Which made way more sense - it was having traffic with the powers of the warp/daemons that was the problem. The whole take on that in the HH novels was weird and was not a logical change, since basically everyone kept having psykers and/or needed them to fight chaos.
    – Marbrand
    Commented Aug 30, 2018 at 7:17
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    Oh shoot. Quite right, @Brian. Thanks for the correction. Commented Aug 30, 2018 at 12:59

4 Answers 4


Magnus was created to sit atop the golden throne, he and the Emperor are the only beings capable of surviving it. The 15th legion were formed from the geneseed of Magnus, thus they became psykers.

Why he would also make a legion out of them is best explained when looking at the Thunder Warriors, they too were planned to be obsolete from the start yet during their lifetime they would have purpose in the Emperors plan. Just as the Thunder Warriors were cleansed when their time finally came so would the Thousand Sons probably be when the great webway project would have been completed. (If Magnus hadn't irreversibly damaged the golden throne that is).

  • 1
    I fixed some minor spelling mistakes and forced the paragraph where you created one. I'm unsure if some of the "groups" should be capitalised so left it alone for now.
    – TheLethalCarrot
    Commented Aug 30, 2018 at 9:14
  • yeah thank you, was about to edit it myself when i saw the work was already done for me :) Commented Aug 30, 2018 at 9:17
  • +1 - The only thing I would add in this answer is reflected in comments above regarding Nikaea: the plan was not to outright ban psykers, otherwise then even something would have needed to be done Imperium wide about them, not just the librarians in the legions. The council was looking to address sorcery or the abuse of psyker abilities in general. In addition, it would have made Wyrdmake's testimony (a psyker himself) against the Thousand Sons rather curious...
    – Odin1806
    Commented Aug 31, 2018 at 17:28
  • @Odin1806 only thing is that the space wolves rune priests actually believe they themselves aren't psykers at all. Pretentious bastards :P Commented Sep 10, 2018 at 8:10

The Emperor didn't want Magnus and his sons to explore beyond a limited understanding of the warp. Obviously he knew Magnus was psychically gifted, but--and this is the most perplexing thing about 30k--the Emperor sincerely believed he could and should have shielded his Primarchs from learning the true nature of Chaos.

It's a fairly naive plan if you think about it. The nicest thing you can say about the Emperor's control of warp knowledge is that he meant well... but it's also the fundamental ignorance that led to Horus'fall and Magnus' eventual doom when warning his father.

By being so controlling, the Emperor blew his plans to smithereens. He's a crappy father. If he actually took the time to understand many of the sons who fell, such as Magnus' inquisitiveness, he might have been forestall the failures and corruptions that undid the Great Crusade.

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    The Emperor's lack of openness is especially confusing after the Primarchs were scattered. At that point he knows someone is working against him, but appears to become even more withdrawn rather than warning the targets of chaos that they are under attack.
    – Jontia
    Commented Aug 30, 2018 at 8:49
  • +1 for smithereens (and also because I like the answer, but mostly for smithereens).
    – Daft
    Commented Oct 26, 2018 at 9:21

In Master of Mankind the Emperor doesn't tell Ra he only intends for himself and Magnus to be the only Psychers what he says is that his aim is to Shepard Humanity into the age of psychic powers. He wants to remove humanity's reliance on the warp by introducing the webway and then over millennium teach Humanity to use there psychic powers safely. Nikea was imposed because he saw humanity was rushing ahead with psychic powers without truly understanding them.


The main reason that the Emperor wanted to use the webway was that it was better in many practical respects. The webway was safer, faster more reliable and didn't require industrial sale human sacrifice.

Warp travel was dangerous and unreliable which made running a galactic empire difficult. The Great Crusade was necessary in the first place because long range warp travel had been all but impossible for millennia because of warp storms in the aftermath of the creation of Slaanesh. Access to the webway would prevent that from happening again. Indeed during the Heresy Horus was able to orchestrate warp storms which isolated loyalist forces and made his passage to Terra easier.

It's not clear that the Emperor intended to do away with psykers altogether, after all it is an innate ability and they were going to be born whether he liked it or not. What he did want was to make sure that their powers were used in a safe and controlled way.

He also had a dilemma in terms of dealing with Chaos. The idea of the imperial truth was to significantly reduce the power and influence of chaos which tended to infiltrate cultures via religion and superstition. However it was in a fundamental self-contradiction since it relied on denying the existence of forces which did indeed exist which mean that mankind was also ignorant of it's dangers one one hand while, at least partly, removing the temptation to mess with it on the other.

There is a reasonable argument that the 15th Legion represented exactly what he wanted human psychic power to be, ordered, disciplined and well regulated. There are also hints in the lore that psychic powers aren't necessarily intrinsically intrinsically linked to the Warp. The Space Wolves continued to use Rune Priests after Nikea, claiming that their power came from Fenris not the Warp and the White Scars make a similar claim. This seems to be borne out at least in part by the fact that Space Wolves seem to be very resistant to Chaos Corruption.

There is also the consideration that despite it's risks psykers were one of humanity's most effective tools for fighting Chaos and once demons started to take a large scale part in the Heresy most Librarians were reinstated.

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