Beatrice was created four hundred years ago by Echidna, the Witch of Greed. Echidna, whom Beatrice considered her mother, eventually left Beatrice in charge of the Forbidden Library where she was meant to diligently wait for a person known only as "They".
Beatrice waited four hundred years for "They" to show up, keeping her desires to abandon her assignment inside. Eventually, Subaru Natsuki convinced Beatrice to abandon her mother's mission and become his contracted spirit.
Since then Beatrice has gone on many adventures with Subaru and has become his closest confidante in the world.
Despite her long life, Subaru described Beatrice as looking as though she was around eleven to twelve years old. She has large sky-blue eyes with pink butterfly patterns in their centers. Her blond hair is tied with pink ribbons into long drill-shaped pigtails which have pink tips in the anime. Subaru believed that there was no heart that wouldn't melt at the sight of a genuine smile on Beatrice's face.
Beatrice sports a petite crown on the right side of her head. She wears a frilled dress with white trimmings and an open front. Her legs are covered by pink and purple-striped tights and she wears pink shoes. A giant pink butterfly-shaped ribbon is attached to the side of stomach.
Beatrice generally looks down on others and is bad at dealing with people who try to get close to her. Despite being full of bravado, she's a lonely person, and is softhearted beyond her perceived stubbornness. She is affectionate towards Puck because of their similarities and favors him over the others in the Roswaal household. She has a distinct way of speaking, adding "I suppose" at the end of some of her sentences. She also refers to herself in the third person similar to Ram and Rem.
- Her appearance is set. So even if she changes her hairstyle it will revert back to the drill-like pigtails.
- Beatrice shares the same attribute with Subaru which is why they're highly compatible in terms of being a spirit and contractor.
- She used to rarely show up for dinner, but ever since Subaru arrived and after events of the demon beast incident, she has been showing up more frequently.
- As a spirit she doesn't need to eat, but she does enjoy the pleasure of it.
- Beatrice shares similaries to Odelia from Atelier Ayesha: Alchemist of Dusk:
- Both are several centuries old.
- Both reside in a library that contains high amounts of knowledge and are tasked with guarding it by their masters.
- Both felt the isolation/loneliness of their duty and hope to one day be freed.
- Both possess a stoic demeanor, but their emotions will pique when interested (Puck for Beatrice and sweets for Odelia).
- Both were eventually able to outlive their purpose after meeting the main protagonist and will aid said character.