"...our Chapter is in the hands of a mad man, and a Heretic, Azariah Kyras. He who should be the greatest of us all, has bargained away his soul. Brothers, this cannot, this will not stand." -- Captain Gabriel Angelos of the Blood Ravens Chapter
Azariah Kyras is the former Chapter Master and Chief Librarian of the Blood Ravens Chapter of Space Marines. Kyras is now known by elements of the Blood Ravens to have been corrupted by Chaos. He was finally slain and replaced by Gabriel Angelos after the Blood Ravens successfully cleansed the Aurelian Sub-sector of the Korianis Sector of the taint of Chaos with the aid of the Inquisition and the forces of the Imperial Guard.
Azariah Kyras has an unusually mysterious and dark past for the Chapter Master of an Adeptus Astartes Chapter. Early in the 41st Millennium, almost 1,000 standard years before the present, the world of Aurelia in the Aurelian Sub-sector of the Korianis Sector was swallowed by a vast Warp Storm. Before the storm swallowed the planet within the Immaterium, it had been pushed out of its standard orbit and much of its population had died as a result of the sudden frigid environmental changes. Azariah Kyras was a Librarian of the Blood Ravens Chapter serving alongside his master Moriah, the Chief Librarian of the Blood Ravens. Just before Aurelia was swallowed by the Warp, a Greater Daemon of Nurgle named Ulkair, a Great Unclean One, had manifested on the world and had slain Moriah. Weakened by Moriah, Ulkair was vulnerable enough to allow Kyras to imprison the immensely powerful daemon. Then the Warp captured the world and Azariah Kyras along with it.
Many centuries later, the 5th Company of the Blood Ravens had taken serious losses from the groups of Tyranids and daemons that infested a Space Hulk known as the Judgment of Carrion they had been tasked to explore. Azariah Kyras suddenly appeared amidst his fellow Blood Ravens on the Hulk and used his abilities to aid Apothecary Galan, the remaining ranking officer in the company, in defending the surviving Battle-Brothers from the Hulk's hideous inhabitants. The remains of the 5th Company, despite Kyras' aid, were still trapped on the Space Hulk, unable to get back to their Thunderhawks and escape. At the same time, Galan found himself haunted by a malignant daemonic presence that Kyras identified as Ulkair, the Greater Daemon that the Blood Ravens had suffered terrible losses imprisoning and which had caused Kyras to be lost in the Warp for centuries. Kyras, corrupted by Chaos during his long imprisonment in the Warp with Ulkair, sought to corrupt his fellow Battle-Brothers by enhancing their despair and playing on their fears. To gain the escape of the remains of the 5th Company from the Judgment of Carrion, Kyras entered into a pact with Ulkair in which in return for the Blood Ravens' escape from the Space Hulk, Galan was willingly possessed by a daemon. After the remains of the 5th Company escaped from the Judgment of Carrion, both Kyras and Galan were hailed as heroes of the Chapter and Kyras was welcomed back into the fold as a lost Battle-Brother. Yet one Astartes, Captain Gabriel Angelos of the 3rd Company, remained highly suspicious of Kyras, believing him to be tainted by Chaos. Yet Kyras rose quickly back through the ranks of the Blood Ravens because of his great experience and eventually became both the Blood Ravens' Chapter Master and their Chief Librarian, holding both positions simultaneously. Kyras' strongest ally amongst the Blood Ravens, the Apothecary Galan, became the Chapter Honour Guard's Apothecary.
It was the invasion of the Aurelian Sub-sector by a warband of the Black Legion that finally revealed Azariah Kyras' true allegiance to Chaos. Blood Ravens of the 4th Company tracked down and boarded the Judgment of Carrion to learn the truth of Kyras' and the 5th Company's escape from the Space Hulk. The Blood Ravens gained evidence of the pact made by Kyras and Galan with the daemon Ulkair. Kyras himself was not present in the Aurelian sub-sector during the Chapter's Crusade against the elements of the Black Legion. Instead, he sent Apollo Diomedes, the Captain of the Blood Ravens' Honour Guard, to order the Blood Raven forces in the sub-sector to withdraw from all contact with the Chaos Space Marines. Yet, the Blood Ravens officer who served as the Chapter's Force Commander in the Aurelian Crusade turned against Apothecary Galan, who confessed to his own corruption by Chaos as well as Kyras' true allegiance. But Galan explained that Captain Diomedes was untainted, though much of the Honour Guard did serve the Ruinous Powers and Ulkair in particular. The Force Commander and Captain Angelos disobeyed their corrupted Chapter Master's orders and remained in Aurelia to defeat the Black Legion and end the threat of Ulkair.
With the defeat of the Great Unclean One on Aurelia, the Force Commander and Captain Angelos went renegade, determined to bring down Azariah Kyras and the other Chaos-corrupted Blood Ravens, no matter the cost