Oh come on, dont vote if you dont know the armies
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But for your benifit:
(Ripped from Encyclopedia)
"Legend has it that the Grey Knights were founded on the order of the Emperor himself, at some point between the start of the Horus Heresy and the events of the Second Founding. Though it is uncertain about the details (see below about origins), it is thought that the Emperor ordered the creation of a force designed to fight Chaos[1]. It was not until after the Horus Heresy that a force specializing in fighting Chaos was provenly necessary.
Originally they were thought not to be descended from any of the original twenty Space Marine Legions, having been created from a unique gene-seed, rumored to come from the Emperor of Mankind himself[1].
Another possible source for their gene-seed is a purified 'cocktail' of the eight loyal Space Marines from the traitor legions, presented to the Emperor by Malcador the Sigillite, during the Siege of the Emperor's Palace. Malcador had been charged by the Emperor to gather a group of people whose loyalty, courage and strength of mind was unquestionable. The resulting eight marines possessed paranormal skills that were kept dormant (in respect of the Council of Nikaea's previous ruling) and had cast aside former loyalty to legion and Primarch. The Emperor is believed to have responded, "Malcador, you have judged well. These eight Space Marines do indeed have a vital role to play in the future of the Imperium, though veiled in secrecy will they be."
Ironically designated Chapter 666 (according to Codex: Daemonhunters), the Grey Knights are permanently attached to the Ordo Malleus branch of the Inquisition[1]. The Grey Knights are unique among the Space Marines as the only chapter to have full knowledge of the dark secrets of Chaos - they alone completely know of and understand the existence of Daemons and of their appearance in the real world, and they alone are best equipped to battle and defeat mankind's most terrible enemy. While other Chapters and Imperium forces have some knowledge of Daemons and how to fight them, only the Grey Knights are privy to the darkest, deepest secrets that the Imperium knows of these creatures and how to defeat them[1][2].
In the Chapter's long history the Grey Knights hold the highest honor of all: not one Grey Knight has ever turned to Chaos, or betrayed the Emperor.
Due to their secret nature, little is known about their operations. Under the great monastery fortresses on Titan lie countless heroes of the Imperium, though few outside the Inquisition, even outside the Grey Knights themselves, would ever know they existed."
In other words they are special, pyker, Space Marines who hunt demons. (spelt deamons)
Also: The Chaos STINK, they are creepy, weird, and heretic, demon worshipping weirdos. (Yay normal Space Marines they rock)
. I like the Tau because you can have all sorts of stragteys with the Crisis Suits and the Stealth Armor, and the Devilfish covering the Fire Warriors Combo.
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