[@BCTheEntity] That is a rather complex question, but to make it shorter and less boring, psykers are picked especially to become 'ordained' monk-warriors on their home world - even if they don''t really see it as psychic powers, more like...gifts from the Divine Wind, I suppose - the majority of the temple-cities armed forces that [b]are not[/b] part of the middle-tier warrior caste being either peasant levies or lay-monks AKA all those monks in the temples that aren't psykers/haven't reached enlightenment (and never actually will or can, at least not in the way that their superiors have).

On their home world it is these monks, gifted with divine powers at birth, that make up the ruling councils and hierarchy. So it follows into the legion, pretty much all of them being native-born sons of Twenty-Three Sixteen and not Terrans.

Out of interest, is there any way/method of conversion by which one can become a psyker in 40K? 

I [i]was[/i] originally going to have those most 'enlightened' of the XVth able to sort of 'unlock' their latent psychic powers, but as you correctly pointed out this probably isn't even possible/plausible.


[@Hank] I appreciate that, meus amico! Not really sure what you're talking about, but I take every scrap of praise I can get. :lol