Byleth is the main protagonist in Fire Emblem: Three Houses and a major antagonist in Fire Emblem Warriors: Three Hopes. As an Avatar, their name, gender, and birthday are customizable. Byleth serves as a professor at Garreg Mach Monastery. They possess the mysterious Crest of Flames and can wield the Sword of the Creator. Byleth has a very subdued personality and has difficulty expressing emotion. As a newborn, they neither laughed nor cried. People they are especially close to, such as Jeralt, are able to tell how they are feeling despite their limited emotional visualizations. A handful of their students note that their outward expressions hardly vary. Some express surprise whenever they simply smile. According to Alois, this trait of theirs may in part come from their father, as Jeralt does not show his emotions easily either and can also be difficult to read. However, in the support conversations between Byleth and Jeralt in Three Hopes, Jeralt notes how similar Byleth is to their mother Sitri, who like Byleth had difficulty expressing emotion. Their stoic demeanor slowly changes over the course of the Academy phase. Jeralt notices that they have become more expressive over the first few months, likely a result of the bonds they have formed with their students. Despite appearing indifferent, Byleth can be perceptive of their students and fellow faculty's problems and serve as a great source of emotional support for their issues. As the story unfolds, their emotional expression becomes more dynamic, including sorrow, vengefulness, and happiness. Because Jeralt sheltered Byleth 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 their earlier years in their father's mercenary corps for being a fearless and skilled warrior, gaining the moniker of 'Ashen Demon', due to the way they seemingly emotionlessly cut down their enemies in combat. This seems to be somewhat of a sensitive subject for them, as they seem uncomfortable when Hanneman mentions their moniker in their C support. It is notable that in the beginning of the game, Sothis refuses to let the player progress if they do not acknowledge their humanity to her, refuting the "Ghost" and "Demon" options, so it can be inferred that Byleth is uncomfortable with the Ashen Demon moniker because it dehumanizes them. The three house leaders of the Officers Academy attest to their martial prowess and have deep, profound respect for their abilities and guidance in battle and in the classroom. They alongside the other students continue to refer to them as teacher or professor even after the time-skip. The three house leaders also deeply regret that Byleth had not chosen their house if they are not teaching theirs, seeing the value in their strengths. According to both genders of Byleth in Heroes, they do not actually know the distinction between a friend and an ally due to their unusual childhood. Nevertheless, they are well liked by the student body, even those not in in their initial house. Their wisdom ultimately shapes the outcome of the events of Three Houses providing council and guidance to the house leader they chose to teach, helping to shape them into better warriors and leaders. Several students can develop an interest in them and eventually switch over to their house if not already in them. This results in them also joining their faction during the War, even those from enemy nations defecting to their cause, thus changing their fate. Those who do not join will often express regret facing them in battle. However, some students and faculty members, especially in the Crimson Flower route, will instead express outrage at them, vowing to kill them by their own hands. According to their profile in Cindered Shadows and Three Hopes, Byleth has interests in helping and listening to people, likes their father, swords, reliable allies, smiles, and being trusted, and has no apparent dislikes. However, they point out in their expedition dialogue that they detest senseless killing, and if someone were to harm their father, they could never forgive them, which is indeed true for both games.