Knight with gold and grey armour.
The Grey Knights are a secret, mysterious Loyalist Chapter of Space Marines specifically tasked with combating the dangerous daemonic entities of the Warp and all those who wield the corrupt power of the Chaos Gods. They have the honour of being implanted with gene-seed engineered directly from the genome of the Emperor Himself. The Grey Knights act as the military arm or Chamber Militant of the Ordo Malleus, the Daemonhunters who form the oldest branch of the virtually omnipotent Inquisition. The Grey Knights’ fortress-monastery is based on Titan, the largest of the moons of the gas giant Saturn in the Sol System, that is kept as a private preserve of the Inquisition. The existence of the Chapter is virtually unknown outside of the Inquisition and the highest echelons of the Imperial Adepta, and is a well-guarded secret enforced by mind-wipes and even assassination of Imperial citizens if necessary. Unlike other Astartes, every Grey Knight is a potent psyker. Yet, in the 10,000 standard years of Imperial history, no Grey Knight has ever been corrupted by the Ruinous Powers of Chaos.