Beatrice is a member of the Emilia Camp and the former caretaker of the Forbidden Library at the old Roswaal Manor. She is an artificial spirit created by the Witch of Greed for unknown reasons. 400 years ago, she was told to wait in the library for "That Person" who would grant her salvation. However, Subaru convinced her to live, and she became his contracted spirit. On the outside, Beatrice seems like a lovely young girl around the age of eleven or twelve. Her face is so sweet that Subaru believed there was no heart that wouldn't melt at the sight of a genuine smile of hers. Her large sky-blue eyes have pink butterfly patterns as their irises. Beatrice's pale cream blonde hair is worn long and tied into frilly vertical drill-shaped twin tails that act like springs when pulled on. In the anime adaptation, the tips of her twin tails are dyed pink. Most of the time, the Great Spirit of the Forbidden Library can be seen wearing a pink frilly ornate dress with white trimmings and an exposed front that leave her legs visible and are completely covered by pink and purple vertically striped tights. A petite crown is also sported on the right side of Beatrice's large head, serving as a nice accessory which complements her appearance rather perfectly. Beatrice also wears pink shoes with butterfly straps on her feet, and has a large pink ribbon adorned upon the left side of her waist and a pair of similar ribbons tied at the top of her twin tails. Beatrice has a tendency to look down on those around her, to the point that she would come off as a haughty person to people she meets. As such, this makes her rather bad at dealing with people who try to get close to her, like when she first met both Ryuzu Meyer and Subaru. She usually speaks, in the third person, referring to herself as Betty. She is also prideful of her vast knowledge of yin magic, disliking when someone disrespects it, and she also displays pride at being Echidna's daughter, though this would at times lead her into spats with others Echidna had taken a liking to. She has also shown a mischievous side of herself; when she messed around with Ryuzu, she cast a yin magic looping spell to pull a prank on her, and she did the same to Subaru when she found herself somewhat annoyed by the commotion his presence initially caused for her. That said, when a prank is done back to her or someone sees through it, she becomes annoyed quite quickly. She has also shown tsundere tendencies, acting haughty around people she was close to yet disliking showing her sensitive or weaker side of herself, which has come to light with both Roswaal and Ryuzu. That said, she is softhearted beyond her perceived stubbornness. She also has a distinct way of speaking, adding "I suppose" and "in fact" at the end of most of her sentences. She had believed that Subaru might even be "That Person". Eventually, she was finally forced to confront her loneliness when Subaru attempted to bring her out of the manor. Despite wanting Subaru to be "That Person", his declining the notion every time caused her to kick him out of the library, and she was resigned to let herself die as the mansion burned down, her last act being to prevent Subaru himself from dying. However, when Subaru showed his efforts and refused to let her be alone, wanting to leave an impression on her so strong that she would remember him, even long after he died, though he wasn't "That Person", he convinced her to choose him as her person, and she followed him out of the Forbidden Library, forming an official contract with him and fighting alongside him. Following the creation of her contract, Beatrice has shed her loneliness entirely, showing a significantly more cheerful attitude than before. She has shown great pride at being Subaru's contracted spirit, and she would often accompany him and take part in many of his moments of playfulness, trust in his decisions involving heavy topics like accepting Spica in spite of her past, or even become enraged on his behalf when someone mocked the memories of someone dear to him, not even wanting him to meet with said person in the belief that he would be irreparably harmed. She would at times sleep in his bed like a little sister, hold his hand often, and at one point, she almost followed him into the bathroom due to a sense of not wanting to be apart from him. She also has become significantly more social with the other members of the Emilia Camp, though she is also weak to people who give her gazes as earnest as Ryuzu once did. Though she remains filled with her own pride and still is shown respect, she has shown to exhibit a sisterly attitude with Emilia, has become friendly with Petra Leyte, and will regularly tease Otto Suwen in much the same way that Subaru does. This side of her has also led to her providing knowledge to others over topics that she was aware of or chiding Roswaal for his actions, both involving his past bodies and his attitude toward Subaru obtaining more Witch Factors.