Board Thread:Warhammer 40k General Discussion/@comment-25618639-20150627031101/@comment-6078851-20150627132534

i think emps' physiology is normal - as in maybe 6' 2", 1 heart, 2 lungs etc. although the primarchs and astartes were created from his own genome his own body wasn't subject to any bio-engineering (or at least no bio-engineering until such time as the tech became available). given that he was already 8000 years old when the concept of bio-engineering was put forth, i doubt he would have needed any augmentation.

i'm of the opinion that the percieved scale of emps is just that - percieved: his mind is the amalgamation of all the psykers that remained, and with the psychic power this endowed him with it had a physical affect on his genome - his lack of ageing for example. but i think his psychic might was/is so potent that any human who encounters him is overawed by his presence, a presence that is unlike any human before or since, and their minds report this presence as 'giant'.

of course it could also be that he did grow up to be around 14 foot tall, but with his psychic power he would have been able to psychically mask his physical stature.

as for what he knew, well... maybe the gods know :)   he wasn't/isn't omniscient, and while there's plenty he doesn't know there is probably no human who could even comprehend the sheer breadth and depth of his knowledge (including malcador).