Adeptus Custodes - Custodes Creation and Training: As has been mentioned, the Custodian Guard and the Space Marines are related in form, as perhaps might be expected of works of the same creator's hand, but they are very different in function and capacity. There are of course similarities between the two. Both are physically transformed well beyond "natural" Human limits in terms of strength, endurance and fortitude, and fitted for inhuman environmental adaption and resilience, though in this the Adeptus Custodes are the markedly superior of the two in might, if not in adaptability.Both are subject to extensive psychological and cognitive conditioning, and are physically and mentally reworked to render most of their baser drives inert and their beings rechannelled towards aggression, goal acquisition and the fulfillment of duty. As a further safeguard against distraction and as a biological control, both are of course incapable of procreation. In both cases all that is left are beings of singular purpose; in the case of each Astartes, what is created is a living engine of conquest that cares for little else, and in the Custodian Guard, each is created protector of unrelenting diligence and savage capability -- a watchman or watchwoman whose vigilance will never tire.What also differs truly between the two, Custodian Guard and Space Marine, is not just their functional purpose, but the extent of their augmentation and the means by which it is accomplished. While the process through which the Adeptus Astartes are fabricated from a Human being is well-enough documented in its outline, though its details are, of course, rightly held secret by those parties involved in the process on a Chapter by Chapter basis, genuine facts about the manner in which the Custodian Guard are created are very few, even within the hands of the Imperium's hierarchy. This is because -- as with all else about the Custodian Guard -- it is a matter for the Imperial Household alone, and that authority is one none may gainsay or question. What is known, however, marks them as different.Firstly, there is the matter of the age of the candidacy. For a male or female child to become one of the Adeptus Custodes, it is known that they must begin the process in their late infancy and certainly before adolescence has taken hold on their physical structure. This stands in stark contrast to the Space Marines whose implantation with the gene-seed is only possible after the onset of male adolescence and best served before the candidate reaches his full physical maturity.This may link to a second of the few known facts about the creation of the Adeptus Custodes: that the gene-craft and alchemistry that transforms them is as absolute as it is subtle, and worked upon the smallest conceivable microscopic level of their genome and cellular structure. It is a process that effects such change on the mortal Human form that, when complete, unless they suffer such massive bodily harm as to forcibly end their lives, they are effectively immortal, without perceptible ageing taking place after full maturity.Not then for the Adeptus Custodes the pattern of surgical grafting and organ implantation that creates a Space Marine, no such crudities of augmentation at all mar the Custodian; what creates them is as invisible as it is potent, worked upon the core genetics and at a deep cellular level, and perhaps tailored to each specific inductee. There are those who insist that so invisible and yet so powerful is this process that it crosses over into a metaphysical realm of biomancy and psychic manipulation on a level unguessed at. Given that it is said that the Emperor Himself has overseen the creation of every single Custodian Guard who has ever lived, this may well be true.The peerless warriors who then result from this arcane process are a rare breed indeed, and not to be squandered recklessly on the battlefield. They were created with a single purpose in mind; to be the Emperor's own elite guard. They were a force created both to defend the Emperor from physical harm wherever the Great Crusade might take Him, to stand watch over His private domains and most guarded secrets, and to serve as the direct agents of His will -- as His personal emissaries -- be that will to protect, to venture, to claim, to keep secret, or to execute without remorse.Each Custodian is further blessed with protections that leave them resistant to the powers of both the psyker and the Null, making them perfectly suited to fight alongside the Sisters of Silence. Additionally, they never exhibit psychic powers of their own as, though battlefield psykers are undoubtedly powerful living weapons, they are also incredibly unstable ones. Their minds are prone to invasion by Warp entities, and this is a danger no Custodian will ever face. It appears that the Emperor wished for no chink in the defences of His bodyguards, thus granting them no gift of psychic ability.