Priscilla is a central antagonist in the anime Claymore and one of the most powerful beings in the story. Before her transformation, she was a Claymore warrior of extraordinary promise, assigned as No. 2 within the generation of the legendary warrior Teresa. Even as a recent recruit she displayed immense talent, rising through the ranks within months of receiving her mark and pushing the experienced warrior Irene into the No. 3 position. Like Teresa, she could fight hordes of yoma while keeping her yoki suppressed, and her potential was such that the Organization regarded her as a leading candidate to become the next No. 1.

Her background is marked by tragedy. As a young girl she lost her family to a yoma attack, an experience that filled her with an intense hatred of yoma and a rigid, black-and-white view of the world. She believed strongly that the Organization's rules represented justice and approached her duty with a serious, earnest sense of mission. At the same time, she was emotionally immature and mentally fragile, disliking tactics such as surprise attacks and reacting with intense agitation whenever her sense of right and wrong was challenged.

Her defining moment comes when she is chosen as part of a squad of warriors sent to execute Teresa, who had broken the Organization's law by killing humans. During that battle Priscilla is overwhelmed and defeated, and Teresa shows her mercy by sparing her life. The humiliation of defeat, combined with the pity shown to her, drives Priscilla beyond her limit. She loses control and awakens, transforming into an Awakened Being. In this new state she kills her fellow warriors Sophia and Noel, and then she kills Teresa herself, an event that becomes the defining tragedy for the young protagonist Clare, who witnesses Teresa's death. From that point onward Priscilla is known as the One-Horned Monster and is regarded as the most powerful Awakened Being in existence, surpassing even the three Abyssal Ones who control large territories across the land.

After awakening, Priscilla's personality changes completely. The earnest and idealistic warrior gives way to a being driven by childish cruelty and an overwhelming, insatiable hunger. She feeds on others instinctively, destroys without restraint, and reduces everything around her to emptiness. She represents an absolute wall of despair and destruction, and both the Organization and the other great powers treat her as a threat that cannot be controlled. Her mere existence reshapes the balance of the world and drives much of the later conflict in the story.

Her relationships are essential to understanding her role. She carries a deep fear connected to Teresa, the only opponent she ever genuinely feared, and this dread lingers even after she awakens. For Clare, Priscilla is the archenemy who took Teresa's life and later destroyed the village where Clare had found refuge, making her the direct target of Clare's journey of revenge. The two are bound together as opposites, since Clare carries Teresa's flesh and power within her own body. Later in the story, Priscilla suffers a mental regression to a childlike state after a battle with the Abyssal One Isley, who had fought her and, after being defeated, chose to serve as her guardian and follower, containing her as best he could. In this diminished state she wanders the wilderness and comes to travel with the young human Raki, who does not know her true nature. She keeps him close for a time, drawn to him as someone who might one day be able to end her existence, and he unknowingly becomes a temporary link to the humanity she has lost. Over the years without feeding, her body shrinks, and she continues to rely on her keen ability to sense yoma while traveling with him, until a battle involving the fused remains of other awakened beings causes her memories to fully return.

In terms of abilities, Priscilla's power is exceptional on every level. As a warrior she could conceal her yoki so completely that even highly skilled sensors failed to notice her presence, and she could defeat yoma without releasing any of her power reserve. As an Awakened Being she develops a single horn on her head, and her monstrous form continues to evolve over time. In the anime adaptation she later reveals an even more powerful awakened form, becoming taller and more muscular, with larger wings, a longer horn, and retractable green blades that extend from her forearms. She possesses nearly limitless regenerative ability, healing from wounds that would destroy ordinary warriors almost instantly. She can absorb surrounding matter and reshape her own body in ways that transcend normal limits, and the claymore she once carried eventually becomes part of her flesh and blood, allowing her to form a living blade from her right arm even in human form. She is also capable of manifesting copies of herself that attack enemies in large numbers. Her vast and seemingly inexhaustible yoki makes her nearly unstoppable, and throughout the later story she functions as the absolute obstacle that even the strongest warriors cannot overcome on their own.

Priscilla's development over the course of the story is that of a being caught between monstrous instinct and fragmented memories of who she once was. In her childlike state she shows faint signs of attachment and vulnerability, particularly around Raki, and when her memories return she is finally forced to confront Clare, who now embodies Teresa's power. Her arc explores whether a being defined by terrible actions can change, whether the person she was still exists beneath the monster, and whether her destruction can bring resolution to the grief she caused. In the end, her fate is inseparable from the legacy of Teresa and the conclusion of Clare's revenge, and she stands as a tragic, overwhelming figure whose power and suffering define the darkest currents of the story.