Cassiel Morr was a young noble from the small Feudal World of Iblis III in the Endymion Cluster of the Ultima Segmentum. As they are a relatively isolated world bereft of much of the technology and population that would make them a valuable target for the rebels of the Badab War, Iblis III remained somewhat removed from the greater war around them. However, the world does sport an insufferably persistent infestation of Feral Orks, which keeps the local population hard pressed to defend themselves against the Hordes that seasonally descend from the high mountains. And when not fighting off the straightforward threat of marauding Xenos, Iblis III has had to suffer the insidious machinations of the Cult of the Sacred Union: a secretive order of Slaanesh fanatics that claim Iblis III as part of their master's domain.

It was to such a world that Cassiel Morr grew and thrived. The eldest son of the Count of Morrstadt, Cassiel grew up with all the privileges of that world's nobility. Not content to rest on his father's wealth and influence, Cassiel was determined to be a worthy protector of his people after a warband of Savage Orks nearly sacked his village when he was a boy of seven winters. Taking to the sword more readily than the pen, much to his father's chagrin, Cassiel became adept at the knightly arts to the point that he joined the Ritters. The Ritters were the knights that served the Planetary Governor, or the Statthalter in the local dialect, and protected the realms of Bretagne from all threats.

Despite his noble lineage and skill at arms, Cassiel might have passed by in obscurity on Iblis III, and never been noticed by the galaxy at large. But fate had other plans. During a routine patrol of the Verdrehte forest, Cassiel's band came across a disgusting ritual in which the Cult of the Sacred Union was attempting to summon a servant of their master and receive its "blessing." The knights put the cultists to the sword immediately of course, but not before the ritual was complete. A Fiend of Slaanesh stepped on the soil of Iblis III, and a desperate fight began. Of the dozen seasoned knights, only Cassiel survived the ensuing melee. Though not without considerable injury. And while they had all collectively managed to barely slay the vile creature, as the only survivor it was was Cassiel who received the glory and honor. Such an act reached beyond the borders of that tiny world, and even came to a detachment of the Charnel Guard fleet at work during the Badab War. The Company Captain saw the makings of a potential recruit, and used their influence to recruit the young knight from his homeworld. While it was known on Iblis III that other worlds existed, experiencing the wonders of technology and the and the vastness of the sea of stars has been an awing and humbling experience for the young man.

For the next twenty years, Cassiel learned the ways of the Charnel Guard. As a Scout, he learned all manner of guerrilla combat in their service, and he acquitted himself well. Eventually he was elevated to the ranks of the Tactical Marines in the 3rd Company. But he was not long with them, for his time as a lowly Scout had brought to focus his deep connection to the darker side of his Chapter. He requested to, and was approved, join the Assault Marines. His apprenticeship lasted nigh on fifty years before he was allowed full status within the holy order of the Sanguinary Guard. For the next thirty years, he performed his duties well, soothing the spiritual turmoil of his brothers and bringing death to the greatest champions of their enemies. It was his actions taken during the The Devastation of Baal that set Cassiel down the path of joining the Deathwatch. His contributions to the Charnel Guard victory over the Tyranids at Verdis Elysia could not be denied. At the conclusion of the campaign, Chapter Master Oroiael Shreck himself praised his faith and skill. For his part, Cassiel had developed a taste for Xenos blood, and only wished to tear into more of them. So to reward him, and satiate him, Oroiael Shreck assigned him to the Deathwatch the next time the call came out for the Chapter to honor their ancient Oath.

Thus came Cassiel Morr to the Deathwatch. And though his initial missions with Kill-Team Nemeaeus were fraught with egos and personalities trying to find their place, eventually they found their unity and their camaraderie. For three years, Kill-Team Nemeaeus served the Eye of Damocles with distinction, until their last mission aboard the Space Hulk Wretched Spire, whose horrors are too terrible to recount here. Only Cassiel emerged alive from the unholy depths of that place. He alone must carry their memory, and continue to honor the oath they all took together, by joining the newly formed Kill-Team Orthus.