Grey Knights - Hidden Chapter: Over the centuries, as the Imperial bureaucracy stabilised following the Great Scouring, the Grey Knights eventually did become the Chamber Militant of the Ordo Malleus.Fashioned in the image of the standard Space Marine Chapters, the Grey Knights' battle-brothers were augmented by the Emperor's advanced science and genetic experimentation. Blessed with both transhuman physiology and the most advanced weaponry, the Grey Knights would be the secret elite of the Adeptus Astartes. However, it would not be enough for them merely to be strong of body and skilled at war, though in this they surpassed even other Space Marines. To fight the Daemon the Grey Knights needed to be pure of heart and mind as well, with an unblemished soul in which the inherent corruption of the Warp could find no purchase. To combat Daemonkind all Grey Knights are trained to bend the powers of the Warp to their will, and each one is a powerful psyker.Mundane blades and guns will not suffice against Daemonic foes, and so the Emperor ensured that the Grey Knights would have the skill to turn the weapons of the Warp against its denizens. Few mortal minds can master the powers of the Warp without becoming infected by the corruption of that nether realm, and many Human psykers end their days wailing in madness or tearing at their ruined flesh with bloody fingers.Grey Knights, however, are unique amongst Mankind in their control of their psychic gifts, their purity of soul and strength of will an impregnable wall against the horrors of the Warp. Even the Librarians of other Chapters cannot match the psychic mastery of each Grey Knight, and must always be vigilant against the insidious threat of Daemonic possession or madness brought about by coming into contact with the Warp.A Grey Knight does not gaze into the Warp and fear what lurks within; rather, the creatures of the Warp recoil from him. Like all Space Marines of the Adeptus Astartes, the Grey Knights are few in number, a mere handful when counted against the vast span of the galaxy and the countless foes of the Imperium. However, even a handful of these expert warriors are enough to turn the tide of a battle or vanquish a determined foe. There are few enemies of the Emperor that can hope to stand against a Grey Knight, even when they outnumber him many times over.Few as they are, the Grey Knights appear only when there is a grave threat to the Imperium from the Warp, often in places where the Dark Gods have unleashed their Daemons upon reality. Theirs is a secret war against the Warp, the true extent of the threat from the Ruinous Powers hidden from most of the Imperium, much like the existence of the Chapter itself.It falls to the Grey Knights to contain the powers of the Warp, sealing breaches between the material universe and the Immaterium or banishing powerful Daemons that have taken physical form. Like a righteous storm of the Emperor's wrath, the Grey Knights will appear out of the void, their sleek strike cruisers plunging them deep into the heart of the Daemonic sore upon reality.With exacting precision and pitiless fury they will purge a world of Daemons, slaying Daemonic Heralds and putting to death the Chaos Cults and Heretics that summoned them. Often the need of quelling a full-blown Daemonic incursion will throw the Chapter into an existing warzone, where they will be called upon to fight all manner of foes other than Daemons.Alien monstrosities, xenos witches and Heretic Astartes -- all fall just as easily to the sanctified Nemesis Force Weapons, blessed bolters and psychic might of the Grey Knights. However, these are merely a distraction from the Chapter's true purpose: the eradication of the Daemon.The Grey Knights are unique amongst the Space Marines as the only Astartes Chapter -- perhaps with the exception of the Imperal Fists successors called the Exorcists -- to have full knowledge of the dark secrets of Chaos. They alone completely know of and understand the existence of Daemons and of their ability to enter realspace, and they alone are best equipped to battle and defeat Mankind's most terrible enemy. While other Chapters and Imperial forces have some knowledge of Daemons and how to fight them, only the Grey Knights are privy to the darkest, deepest secrets that the Ordo Malleus possesses on these creatures and how to defeat them.The existence of the Grey Knights Chapter is one of the most closely-held secrets of the Inquisition. Beyond the Inquisition, only the members of the highest echelons of the Imperium are aware of the Grey Knights' existence, though even they are ignorant of the Chapter's organisation and methods. The reasons for this secrecy start with the policy instituted by the Emperor before the start of the Great Crusade: the existence of Chaos and the Daemonic within the Immaterium was a secret that only the Emperor was to be privy to -- a secret that was only forcibly revealed thanks to the outbreak of the Horus Heresy.The Inquisition, which was originally created for the purpose of waging a secret war against Chaos, applied the post-Heresy Imperial policy of secrecy, which closely followed the Emperor's own, to the entire Imperium. The existence of Chaos, the powerful Warp entities called Chaos Gods and the Daemonic was privileged knowledge which was to be kept from the populace of the Imperium at all costs. This policy was instituted as a way of preventing the spread of Chaos' innate corruption to the sinful and easily corrupted common people of the galaxy.Because of this secrecy, unauthorised knowledge of the Grey Knights' existence by Imperial military personnel or civilians will result in the mind-wiping or execution of the subject, while even an Exterminatus may be considered and applied to a world whose population has learned the truth about Chaos. One exception to this rule is the Space Wolves Chapter, whose full complement of Astartes was granted knowledge of the Grey Knights' existence following the purges of Imperial personnel that resulted from the First War for Armageddon in 444.M41.Few have ever laid eyes upon a Grey Knight and lived long after the experience, perishing soon after either to the forces of the Daemonic incursion that brought the Chapter to their world or the zealous purity of the Grey Knights in the aftermath.Only the Grey Knights can be trusted to resist the lure of Chaos, and while armies of the Astra Militarum, Adeptus Astartes and other soldiers of the Imperium might aid in the destruction of Warp entities, they will likely become corrupted from the experience.Even the smallest risk of Chaos taint is too great to ignore, and Imperial Guardsmen will be executed or subjected to telepathic scouring, while Space Marines might be mind-wiped or sworn to secrecy with the gravest of oaths to their primarch.So it is that when the psychic warriors are spoken of, if ever, it is only as legends and myths. Due to their secretive nature, little is known about the Grey Knights' operations. Yet, deep beneath their great fortress-monastery on the moon of Saturn called Titan lie countless Grey Knight heroes, although few outside the Inquisition and the Chapter itself will ever know that they existed.