Heyya!

I'm working on a new Tech-Priest concept, and playing with the idea of being fairly opposed to the whole Ecclesiarchy-thing. He is a serf at the Libary in Fenksworld.

What I'm wondering about, is what level of what lore I would need to know, that

• The God-Emperor was always against people regarding him as a divine?
• The Imperial Cult started out as a sect, called the Lectio Divinatus?
• The Lectio Divinatus has been written by Lorgar, primarch of the Word Bearers?
• The Word Bearers were one of the first to fall to Chaos?

Is this level of knowledge acquirable at all in Dark Heresy, or is this Ascension-grade?

That is all very Forbidden knowledge. Most Inquisitors would be hard pressed to know any of the later 3, and almost no one knows the last.

Do remember the Imperial Cult has had almost 7000 years since it was made the basis of Imperial Law, and therefore they have had a long time to cover everything up. Consider the Catholic Church. Since the death of Jesus, and then 600 years after, during the Roman reign of Costantine, the Catholic church decided its doctrine, and since then, any real truth in its teachings have been massively masked by what was decided during said reign.

Times those 1.4 thousand years by 5, and you have the situation in the Imperium.

Most Space Marines would be hard pressed to know such knowledge I would imagine.

That being said, it isn't insane to imagine a cult who kept such secrets alive all this time... Especially not in some of the lower sects of the Machanicus, as they originally resisted the Emperor's rule, and then again his veneration.

It all depends, really, on the type of game you're playing. Sometimes, particularly if you have players that are steeped in the lore already, it can help to play a game where the Acolytes become privy to more forbidden knowledge than they otherwise would.

However, I don't think you would ever come across canon instances of acolyte level individual knowing such secrets, and I would generally say those are ascension or post-ascension grade bits of trivia.

It's also worth noting that, in my opinion, your character concept is a little outside the scope of DH, assuming you're talking about the Library of knowing. I also am not sure that those in charge would use Tech-Priests to tend their somewhat-heretical font of knowledge.

(However, I always say:am always of the opinion that you should change the universe to suit your game, not the other way around.)