"...Our Chapter is in the hands of a mad man, and a Heretic. Kyras - he who should be the greatest of us all, has bargained away his soul to the powers of Chaos. And we are branded as renegades and traitors. My brothers, this cannot, this will not stand."
Azariah Kyras was the former Chapter Master and Chief Librarian of the Blood Ravens Chapter of Space Marines. Kyras was tragically corrupted by Chaos following his confrontation with the Greater Daemon of Nurgle, known as Ulkair. Five hundred standard years after his disappearance, he inexplicably returned to his Chapter and seized command of the 5th Company. His experiences within the Warp tragically corrupted the Space Marines, such that upon his return he became intently focused on spreading that corruption to his Battle-Brothers. Over the centuries that followed Azariah Kyras hid his corruption while spreading his taint through the Chapter.
Kyras eventually openly declared his loyalty as a servant to the Ruinous Powers and was granted ascension as a Daemon Prince. Kyras was slain and replaced by the noble Gabriel Angelos, commander of the Blood Ravens' 3rd Company, 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 Astra Militarum during the Second Aurelian Crusade.
Before Aurelian Crusade
Azariah Kyras has an unusually mysterious and dark past for a 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. Then-Epistolary Azariah Kyras was a Librarian of the Blood Ravens Chapter who served alongside his master Moriah, the Chapter Master and 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. While the hideous Warpspawn was overcome, Epistolary Kyras was thought lost to the Warp. His death was entered into the Chapter's records, along with commendations for bravery.
Five Terran 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.
Over the centuries that followed Azariah Kyras hid his corruption while spreading his taint through the Chapter. Those who fell under his sway became hosts for daemons allied with the -- supposedly dead -- Greater Daemon Ulkair. In surprisingly short order, Kyras assumed the title of Chapter Master, taking command of the Blood Ravens and corrupting many of the other Space Marines. At the same time, he forged alliances with other daemons and foul servants of Chaos. Gabriel Angelos -- Captain of the 3rd Company -- was the only member of the Chapter's command elements to view Kyras's return with mistrust. Despite his misgiving, Kyras rose quickly back through the ranks of the Blood Ravens due to 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. Gabriel quietly and suspiciously investigated the Chapter Master at every opportunity, and would ultimately expose the Chapter Master as a heretic and traitor, when he confirmed links between the fallen Battle-Brother and the Traitor Legions. However, the truth was discovered too late. By the time Captain Angelos was prepared to reveal his findings to the Chapter, a large number of its Space Marines were already corrupted. Instead, Kyras declared Gabriel a traitor and initiated a vicious hunt for the Captain and his forces. A bloody civil war ensued, one that would engulf the entire Aurelian sub-sector at its peak.
Second Aurelian Crusade
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. Openly declaring his loyalty to Chaos, Kyras ascended to Daemon Princedom of Khorne by offering all the souls in the Sub-sector Aurelia via the Exterminatus. However, Kyras' ascension was far from complete, allowing a strike team of Blood Ravens to destroy the towers of offering and, thus, weaken Kyras enough to harm him. After a long and difficult battle, Kyras was stunned long enough for an orbital bombardment to occur. The daemon was slain and its plan was thwarted, but at a great cost to the Blood Ravens. Most of Gabriel's forces were slain during the battle and Gabriel himself was viciously struck down by Kyras. His broken body was repaired with extensive bionic augmentations and he was ascended to Chapter Master after a bloody purge. Following the purge, many of the Chapter's unusual practices would continue to be re-examined. The Chapter now must exhibit great care as they recruit new members to replace those who betrayed the Imperium, lest other factions push for their dissolution at this time of weakness.