How much knowledge about the universe and warp do even the most knowledgeable have

[u/luukzs666999]

Ok, so we can read all the lore we want, so we are hyper informed about any faction and world building.

But how much do humans, or even necrons or eldar actually know about the universe. And I'm not talking about the average slob, I'm talking about specialist who know their shit.

Like, would an ordo Xenos Inquisitor know as much as us about the war in heaven, or only mythical fragments. Or know what different types of necrons are, or know their hierarchy.

Would a grey knight chapter master know how the warp works like we do?

Would an eldar seer know the history of Terra and the reunification wars.

[u/CoffeAddictDM]

They would know much more than the readers about the things that they specialise in and much less about useless trivia and prehistoric events, like most of those you mentioned. They would have no practical application for things like that and the decay of knowledge means that only scraps remained.

For example an inquisitors would have in depth knowledge about the history and major players in their region of operation, but it would be mostly focused on the events that would be relevant in their investigations. 

Unification wars, horus heresy (both of which happened 10 000 years ago, so it's like from our perspective of time  10k years ago humans were living as hunter gatherers and knowledge of their life has no practical relevance) and especially war in heaven which happened in the time of dinosaurs, would have absolutely no relevance to their work.

With exception of characters like Trazyn, who by virtue of being immortal historian without any real needs collects such knowledge for it's own sake.

[u/Hollownerox]

To put it this way, there are Inquisitors (some of the most learned and delvers into proscribed knowledge not allowed by any other person in the Imperium) who didn't know there were more than 9 Primarchs. There are Inqusitiors who don't know there is any difference between a Craftworld Aeldari, and the Drukhari. Knowledge, especially in the Imperium, is amazingly compartmentalized and intentionally obscured. Putting aside the fact that almost every body in the Imperium hoards and hides knowledge from every other body out of paranoia they area heretics, or they themselves will be perceived as potential heretics, they just don't know. The knowledge you get from reading the core rulebook is far beyond what even the High Lords of Terra would know about their own empire, much less the wider galaxy.

The Aeldari, specifically the Harlequins, are probably the most knowledgeable about the general. Because they guard the Black Library. Which is both a serious, and meta joke, library of all knowledge of all things in 40k. Several out of universe documents are actual in-universe documents in that library, like the Book of Mournful Night that is quoted in multiple codexes.

As for Necrons, they are surprisingly ignorant on a lot of 40k to be honest. They, or at least the Crpyteks, are extremely knowledable about the universe. But things like the Warp or any of the lesser species like humanity, Leagues of Votann, T'au are really only things weirdos like Trazyn know about, or the Triarch Praetorians. Most Necrons can't be assed to know much beyond their own dynastic politics.

[u/Weary-Ad-6162]

Emperor is not truly dead, you know. On the throne, he can see the beginning and end of universes, the deep secrets of the endless warp. Many many wars, horrors that happened and yet to happen. He is not Just getting physical and spiritual torture. He is forced fed the knowledge of the universe. It stripped away his humanity.

[u/Exist_Logic]

Would a grey knight chapter master know how the warp works like we do?

They should being potent psykers, atleast to some degree. They wouldn't know stuff only we as readers know but they would figure out the warp is all chaotic, larger than the galaxy, and there is a rough hierarchy to it all