Stepping a bit late into the convo so I hope Im not bringing it back a step. If so please forgive me. While I dont know much more about his original background then what is menitoned in the Mechanicum HH
book. I do have a theory on "what" exactly he is.
In the book "The eye of terror" by Berrington J. Bayley ( http://www.amazon.co...s/dp/0671783904
) it is revealed that the Emperor is just like the other gods a manifestation of the human psyche (in his instance the need for order and good). The fact that he has manifested in the materium while the others manifested in the immaterium makes sense to me as the universe would allow for all infinite possibilities, even that of a god manifesting in the materium, especially if he is the god of order and reason. Tzeentch orchestrated the HH
precisely so that the emperor would end up in stasis, neither alive nor dead. The reason for this is that dead he would merge with all the different chaos gods and form one almighty god, while alive his imperial truth would weaken the chaos gods power.
The question why he promotes the imperial truth I believe is as follows. Having manifested in the materium he is subject to its rules just as the chaos gods are subject to the rules of the immaterium and cannot cross over. As a result he isn't all knowing but merely rediculously powerfull psychically. To understand the possible futures of the universe he looks into the warp as mentioned in "Blood games - Tales of Heresy" by Dan Abnett It would make sense to me that he saw Horus betray him because Horus is made to believe that the Emperor wants to be worshipped as a god. In order to avoid this he tries to avoid his worship (and that of all godly powers to weaken the chaos gods at the same time) at all costs by promoting the imperial truth. However due to the nature of the warp and the influence Tzeentch could have on it he probably didn't see exactly how Horus comes to believe that the Emperor will be worshipped as a god and therefore doesn't effectively manage to prevent this from happening.
As to how, when and where he manifested, I think happened as soon as mankind evolved enough emotion for order and reason for him to blink into existence. I imagine this to be waaaayyyy before the formation of nations or the learnings of shamans to create a big spell.
Edited by Chief Librarian Benarius, 12 May 2009 - 07:09 PM.