Raised at the Schola Progenium facility at Antigone's Harbour, Rosetta Anastasia was singled out by the Order Famulous as a potential recruit for the Adepta Sororitas at the age of twelve years. The agents of the Sisterhood were impressed by her pious spirit, which, matched with her latent fighting skills, made her ideal material for the battle sisters of the Orders Militant.
During her period as a Novice, Anastasia was indoctrinated into the ancient beliefs and traditions of the Sisterhood. She learned that the Sororitas had been founded during a distant and tumultuous period in the Imperium's long history, which was brought to an end by the actions of Saint Dominica. She learned of the Greater Orders and their Founding Saints, each of whom was a loyal follower of Dominica, who had then gone on to found the greatest of the Orders Militant, the Order of the Ebon Chalice. She learned of the Lesser Orders Militant, each of which was a daughter-house of one of the Greater Orders. She learned that central to the Sisterhood's doctrine is the knowledge that Mankind stands at a critical juncture in history, and that only through the salvation offered by the Emperor can Humanity prevail against the horrors of the galaxy, and Man's own self-destructive nature. Only through total commitment to the Emperor, can the Adepta Sororitas hold the forces of disorder at bay, and this can only be achieved by submitting oneself wholly; mind, body and soul to the tenets of the Imperial Creed.
At the age of seventeen, Anastasia stood with five hundred of her fellow Novices and took the Oaths of Adherence in the Ecclesiarchal Palace on Terra. The Ecclesiarch himself blessed the assembled Novices in a ceremony that lasted throughout the night, and culminated at dawn with a superior from each of the Orders Militant stepping forward to lead each of the girls off to don the armour of their new Order for the very first time. It was a superior of the Order of the Ermine Mantle that stood before her, and Sister Anastasia left at her side, taking leave of Terra for Subiaco Diablo, the Hive world near the Cadian Gate called home by her new order.
The Convent of the Order of the Ermine Mantle is set at the apex of the tallest spire of Hive Siana, the capital of Subiaco Diablo. Being so close to the Eye of Terror, the Hive world had more than its share of cultists and recidivists spreading the seeds of heresy and corruption within its teeming populace. The Sisters of the Ermine Mantle were engaged in a never-ending struggle against these elements, and so Sister Anastasia saw action within weeks of arriving at her new convent. For the next four years, Anastasia fought at the forefront of the war against Chaos, but it was obvious to all that the forces of the Ruinous Powers were gaining in numbers and fanaticism with each passing month. This state of affairs greatly troubled the young Sister, and she undertook increasingly long prayer-vigils upon the cold stone floor of the convent's inner sanctum, seeking the Emperor's guidance and strength to act against those who sought to drag Humanity down into the pits of ruin of their own making.
In the closing months of the 41st Millennium, matters came to a head. Abaddon the Despoiler, the Arch Heretic united the servants of Chaos and unleashed his Thirteenth Black Crusade. The Hordes of Chaos erupted from the Eye of Terror, smashing into the defences of the Cadian Gate. Upon a hundred worlds, the unseen agents of the Ruinous Powers revealed themselves, sowing discord and confusion amongst the beleaguered defenders at a time when only total unity would see Mankind prevail. The first sign of the invasion came when a plague, the likes of which had never been seen before, swept the sectors surrounding the Gate. The over-populated hives of Subiaco Diablo were soon reduced to charnel houses of disease and corruption, doomsday cults roaming the streets proclaiming the end times for those who did not put their faith wholly in the blessed God-Emperor of Mankind. The cults preached that only those pure in every respect could hope to resist the Plague of Unbelief, as it became known, and set about the purging by flame and bullet of any they believed impure.
Soon a fate far worse than death at the hands of the plague visited itself upon the unfortunates of Subiaco Diablo. Those who had succumbed to the contagion rose once again, in the form of hideously decayed zombies, their recently dead flesh sloughing from their shuffling forms as they fell upon the survivors.
Throughout the plague, the Sisters of the Ermine Mantle remained unaffected, not one of the Sisters being afflicted by it. None that is, except for Sister Anastasia.
As the scrofulous hordes of decaying plague zombies converged upon the convent, a shining beacon of purity amidst the planet wide sea of filth, Sister Anastasia lay in her cell in the grip of a pain-wracked fever. In moments of relative lucidity, she regarded her face in the reflection of her polished armour, and saw upon it the mark of corruption. And so, while her Sisters battled the uncountable hordes at the walls of the convent, Sister Anastasia scourged herself in an effort to draw out the poison she felt deep within. Never in her life had she had any cause to doubt that the Emperor was watching over her, but now she felt further from his grace than if she had crossed the vast gulf between galaxies. Anastasia endured her self-inflicted penitence and the ravaging fever for five days and nights, refusing to allow any of her sisters to enter the cell to aid her; so ashamed was she of her condition.
On the fifth night, at the height of her fever, convulsing in spasms of agony, Sister Anastasia beheld a vision. She saw the Eye of Terror as a vast abscess upon the face of heaven. The Eye opened, and the sore spilled its filth across the Imperium, a tidal wave of corruption sweeping the Emperor's servants aside as they vainly attempted to hold it back. The wave engulfed Cadia, then, world by world, every bastion of the Emperor's armies all the way to Terra. As the mighty wave broke upon the homeworld of Mankind, Anastasia awoke with a cry: her fever had lifted and she felt suddenly cold as the sweat coating her skin cooled in the chill night air.
Donning her armour, Sister Anastasia resolved to stand beside her sisters in the battle against the plague zombies. But as she left her cell, she realised how long she had endured her fever, and that the convent had been decimated by five days of incessant conflict. As she walked the empty corridors, she found evidence of the terrible battle that had raged; bodies lay strewn all about, those of her sisters and the attackers. At length, she came to the central chapel, wherein she found the remnants of the Order of the Ermine Mantle. Fully two thirds of the Order had fallen defending the walls, and the surviving sisters had gathered to give thanks to the Emperor that the enemy had been repulsed.
The knowledge that she had failed to stand by her sisters struck Anastasia like a hammer blow. She sank to her knees before them, tears filling her eyes as she strove to find the words to plead their forgiveness. But the words were as ashes in her mouth.
Staggering to her feet, Anastasia invoked the first verse of the Oath of the Penitent, the words leaving her mouth as a choked whisper. The others gathered around her, and she realised that no senior members of the order had survived the battle: only sisters her own age remained.
As she spoke the words of the ceremony, one of her sisters stepped forward. At the completion of each verse, an item of Anastasia's armour was removed. Seals bearing the words of the oath were attached about her person as another sister took a blade and roughly shaved her hair. Soon, she stood ragged in fragments of her former vestments, blood streaming from her scalp. Her sisters formally turned their backs as she spoke the final verse of the rite.
Leaving the convent, Anastasia walked out into the corpse-ridden ruins of Hive Siana, to seek her death, or her redemption.
At first, all was still on the streets of the hive, but as the sun began to sink, movements in the shadows caught Anastasia's eye. Soon, a low moaning filled the air, and ragged forms shambled from the ruins. The zombies were slow, and Anastasia easily outran them, but found that no matter how far she fled they continued to pursue her. Breathless and desperate, she came at length to the shattered ruins of an Ecclesiarchy shrine, the blasted body of its attendant priest draped over the altar where he had died defending it.
Determined to make her stand at the shrine, Anastasia cast around for a weapon. Seeing that the priest still held a sword in his dead grip, she reached for it as the first of the zombies appeared at the broken gates of the shrine. As her hand touched the hilt, Anastasia was wracked by a terrible seizure, her back arching as she let out a dreadful scream. The ruins around her melted away, and she stood upon a vast plain of shattered bones. Before her stood a man in blood red armour, corruption radiating from him in palpable waves. In his hand he bore a weapon that squirmed and writhed with a thirst for the souls of the innocent. The man seemed unaware of Anastasia's presence, and she realised she was experiencing another vision, though unlike the one in her cell, this seemed to be pointing her towards a specific goal. She knew that the vision was telling her that this man was a source of great evil, and must be confronted if that evil was to be thwarted and Anastasia's redemption secured.
Anastasia snapped out of her vision to be confronted with a plague zombie reaching its filthy hands towards her. Overcome by a holy rage, she lashed out with the sword, cleaving the creature in two with one swing. Soon more of the foul creatures crowded into the confines of the shrine, but Anastasia was an avenging angel, her blade shining as she cut each plague zombie down.
And so, Sister Anastasia began her hunt for the man revealed to her in her vision. Over the course of her quest, other revelations came to her, each showing her the face of an individual whose existence could not be allowed to continue. Anastasia knew that in confronting each of these scions of evil and corruption she was doing the Emperor's work, and with every battle, taking another step on the road to her own absolution.