The Moritat were the isolated killers of the Legions, Space Marines who had drifted so far into the practice of slaughter that they could no longer serve within the disciplined ranks of a battle-line. Wielding paired pistols and moving with lethal, solitary grace, they hunted apart from their brothers, given over wholly to the art of the kill.
The rank was never bestowed so much as recognised, a grim acknowledgement that a warrior had passed beyond the fellowship of the squad into a colder and more personal war. Commanders tolerated the Moritat for their terrible efficiency, unleashing them upon enemy champions and command elements, yet many within the Legions regarded them with unease, seeing in their detachment a hint of what the Astartes might become unchecked.
Among Legions such as the Night Lords, the Moritat's cold appetite for death found a natural home, while others held them at arm's length. In the Heresy, such warriors needed little encouragement to turn their guns upon former comrades.