Byleth Eisner - M

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, he neither laughed nor cried. People he is especially close to, such as Jeralt, are able to tell how he is feeling despite his limited emotional visualizations. A handful of his students note that his outward expressions hardly vary. Some express surprise whenever he simply smiles. According to Alois, this trait of his may in part come from his 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 his mother Sitri, who like Byleth had difficulty expressing emotion.

Byleth's stoic demeanor slowly changes over the course of his tutorship at the academy. Jeralt notices that he has become more expressive over the first few months, likely a result of the bonds he has formed with his students. Despite appearing indifferent, he can be perceptive of his students and fellow faculty's problems and serves as a great source of emotional support for their issues. As time passes, his emotional expression becomes more dynamic, including sorrow, vengefulness, and happiness. Because Jeralt sheltered him 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 his earlier years in this father's mercenary corps for being a fearless and skilled warrior, gaining the moniker of 'Ashen Demon', due to the way he seemingly emotionlessly cut down his enemies in combat. This seems to be somewhat of a sensitive subject for him, as he seems uncomfortable when someone mentions his moniker. It is notable that it can be inferred that Byleth is uncomfortable with the Ashen Demon moniker because it dehumanizes him.

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