Created over 400 years ago by Echidna, the Witch of Greed, Beatrice is an artificial spirit bound to safeguard the Forbidden Library within Roswaal Mansion. Her existence centered on awaiting "That Person," promised to grant her salvation, leading to centuries of isolation that fostered deep loneliness and distrust towards those seeking only her knowledge or power. Physically resembling an 11-12-year-old girl standing 140 cm tall, she possesses cream-blonde hair styled in twin drills (tipped pink in the anime), blue eyes featuring distinctive pink butterfly-patterned pupils, and typically wears ornate pink dresses with tights and a small crown accessory. Beatrice initially presented a haughty, antisocial demeanor, often using verbal tics like ending sentences with "I suppose" (kashira) or "in fact" (no yo). This facade concealed profound loneliness and emotional vulnerability, stemming partly from the sacrifice of her friend Ryuzu Meyer during an attack on the Sanctuary centuries prior. Her few connections included a familial bond with Puck, another of Echidna's artificial spirits, and a distant, contractual relationship with Roswaal, whom she resided alongside but openly disdained. A pivotal shift occurred through the persistent efforts of Natsuki Subaru, who sought genuine companionship rather than exploitation. After Subaru learned of her suicidal despair and the 400-year vigil dictated by Echidna, he rejected the predetermined role of "That Person" but vowed to make her happy. This culminated in Beatrice abandoning the Forbidden Library during its destruction in Arc 4 to form a spirit contract with Subaru. This contract altered her abilities; she can now only draw mana from Subaru due to his damaged gate, significantly reducing her independent magical capacity and necessitating external mana sources like crystals for extended power use. Post-contract, Beatrice evolved into a fiercely loyal and protective partner to Subaru, whom she affectionately calls "Subaru" while he nicknames her "Beako." She openly prioritizes his well-being, often sleeping beside him like a sibling and collaborating on combined magical techniques. Her personality softened significantly: she developed friendships with Emilia (overcoming initial jealousy regarding Puck), cooperated with Roswaal when necessary, and integrated fully into the Emilia Camp. Despite occasional exasperation at Subaru's recklessness, she consistently supports his endeavors, aiding investigations like Anastasia's possession and joining expeditions such as the one to the Pleiades Watchtower. As a Great Spirit specializing in Yin Magic, Beatrice commands formidable abilities including teleportation ("Door Crossing"), spacetime manipulation, gravity alteration ("Murak"), and offensive crystalline stakes ("Minya/El Minya"). Her signature defenses are "E・M・M" (absolute defense via spacetime distortion) and "E・M・T" (mana negation within a radius). While historically capable of combating entities like the Beast of the End, her post-contract capabilities are constrained by Subaru's mana limitations. She retains the extensive knowledge accumulated over centuries guarding the Forbidden Library. Her journey traces a path from enforced isolation to chosen kinship, marked by self-determination and emotional connection.