Mephiston

Before he was Mephiston he was Calistarius, a Librarian of the Blood Angels who fought in the relief of Hades Hive during the Second War for Armageddon. There the curse of his bloodline took him at last, and the Black Rage dragged him down into madness and the ranks of the Death Company. His fall seemed complete when a ruined building collapsed upon him in the fighting, burying him in rubble and leaving him for dead.

For seven days Calistarius lay entombed in the wreckage, poised on the knife-edge between death and insanity, wracked by a thirst for blood that should by every reckoning have consumed him. Yet he did not succumb. By sheer, monstrous force of will he seized hold of the rage that was devouring him and mastered it, and when he clawed his way free of the rubble he was reborn as something greater than the warrior who had fallen. He took a new name, Mephiston, and the Chapter named him the Lord of Death.

The transformation left him all but unrecognisable. His psychic power swelled until it eclipsed nearly every other soul in the Chapter, his strength and speed surpassing those of his battle-brothers, and he rose swiftly to become Chief Librarian and Master of the Librarius. He stands as one of only a handful ever to break the Black Rage and live, and the only one known to have done so a second time when the curse came for him again.

Yet his triumph is shadowed by unease. There are those within the Chapter who whisper that Mephiston did not conquer the curse so much as strike a bargain with something worse, that in the place where the rage once burned there now dwells a colder and more terrible presence. Whatever the truth, he remains a being apart, a solitary Lord of Death whose loyalty is beyond question but whose true nature not even his own brothers claim fully to understand.