Frederica Baumann, born roughly 21 years before the main events to half-beastman father and human mother Reshia Tinzel, possesses quarter-beast human heritage. Following a period of wandering, she, her younger half-brother Garfiel Tinzel, and their mother found refuge in the Sanctuary under Roswaal L. Mathers's protection. After Reshia departed to search for her missing husband, Frederica remained with Garfiel. At age 12, Frederica left the Sanctuary to train as a maid, determined to secure a future home for its inhabitants. She served both Roswaal and House Miload before her dismissal from Roswaal Manor months prior to the main story. She returned at Ram's request following Rem's erasure, resuming her duties as a maid for House Mathers. Frederica possesses very long pale gold hair, green eyes, and a notably muscular build, standing taller than Subaru Natsuki. Distinctive sharp fangs mark her appearance, and she is often considered beautiful when her mouth is covered. She typically wears standard maid attire. In her youth, her shoulder-length hair was unkempt, and she favored a pink dress with a red scarf and socks. During an outing to Costuul, she wore a white and green dress with a green mantle. Her beastification ability allows full or partial transformation into a golden leopard, significantly enhancing her physical capabilities to match Rem's horned state, granting exceptional speed and agility; reversion leaves her in a naked human form. Generally kind yet capable of strictness, especially in mentoring Petra Leyte, Frederica cares deeply for Garfiel. She maintained contact through letters despite their separation during her youth, a time when they often sparred regardless of their seven-year age difference. She acknowledges being less polite and graceful in her past. Her personality reflects strong loyalty, protectiveness, and a powerful sense of duty, frequently prioritizing the safety of those she cares about. She exhibits caution and a need for stability, aligning with diligent and responsible traits in her role. Skilled in melee combat, particularly hand-to-hand fighting often augmented by partial transformation, Frederica possesses an affinity for wind magic she never developed, focusing solely on physical prowess. Her rare blood type poses dangers, making her a target for those seeking to exploit its properties. In Arc 4, Frederica played a supporting role during the Sanctuary crisis. Her involvement deepened in the "Golden Siblings" side story where she and Garfiel encountered Hayden Garo in Costuul. After helping rescue people from a collapsing building, Hayden kidnapped her, intending to use her rare blood to establish a demi-human nation. Garfiel and Clind rescued her; Clind fended off Leonardo Baroness while Garfiel defeated Hayden, though Hayden escaped after Frederica scarred him as a memento. During Arc 5's Battle for Priestella, she attended a meeting with western nobles alongside Roswaal, Annerose Miload, Petra, and Clind. She initially objected to Roswaal having Petra speak for Emilia but relented, and Petra succeeded. In Arc 7 and Arc 8, Frederica joined the Emilia Camp's journey to Vollachia to locate the missing Subaru and Rem, navigating challenges like the Everlasting Darkness with mole humans and negotiating with Musica. Frederica's relationship with Garfiel remains central, marked by mutual care despite separation. She maintains a strained dynamic with Clind, who trained her as a maid; their rapport soured due to her past romantic feelings, though he still shows concern. She mentors Petra in maid duties, occasionally clashing with her. Her loyalty to Roswaal is unwavering, fulfilling duties diligently despite his manipulations. She is part of the Emilia Camp, collaborating with members like Subaru, Otto, and Beatrice. Frederica collects dolls and enjoys dressing them, believing her physique unsuitable for cute outfits. She gnaws on objects to manage her continuously growing teeth. Her blood's rarity is a recurring plot element, with figures like Al isolating her in Arc 9 due to associated risks. A dress she owned was used by Subaru during a cross-dressing incident. Her main story arc is anticipated in Arc 12, as noted by the series author.