Byleth Eisner - F

A stoic professor at Garreg Mach Monastery. Bears the mysterious Crest of Flames.

Byleth has a very subdued personality and has difficulty expressing emotion. As a newborn, she neither laughed nor cried. People she is especially close to, such as Jeralt, are able to tell how she is feeling despite her limited emotional visualizations. A handful of her students note that her outward expressions hardly vary. Some express surprise whenever she simply smiles. According to Alois, this trait of hers may in part come from her father, as Jeralt does not show his emotions easily either and can also be difficult to read. However, Jeralt notes how similar Byleth is to her mother Sitri, who like Byleth had difficulty expressing emotion.

Byleth's stoic demeanor slowly changes over the course of her tutorship at the academy. Jeralt notices that she has become more expressive over the first few months, likely a result of the bonds she has formed with her students. Despite appearing indifferent, she can be perceptive of her students and fellow faculty's problems and serves as a great source of emotional support for their issues. As time passes, her emotional expression becomes more dynamic, including sorrow, vengefulness, and happiness. Because Jeralt sheltered her from knowledge about a number of aspects of the world, Byleth becomes curious about the influence of the Church of Seiros, the mystery of the Crests, and the dynamic of the three nations once they are brought to Garreg Mach Monastery and the Officers Academy.

Byleth has somewhat of a reputation from her earlier years in her father's mercenary corps for being a fearless and skilled warrior, gaining the moniker of 'Ashen Demon', due to the way she seemingly emotionlessly cut down her enemies in combat. This seems to be somewhat of a sensitive subject for her, as she seems uncomfortable when someone mentions her moniker. It is notable that it can be inferred that Byleth is uncomfortable with the Ashen Demon moniker because it dehumanizes her.

The three house leaders of the Officers Academy attest to Byleth's martial prowess and have deep, profound respect for her abilities and guidance in battle and in the classroom. They, alongside the other students, continue to refer to her as teacher or professor. The three house leaders also deeply regret that Byleth had not chosen their house if she is not teaching theirs, seeing the value in her strengths.