Byleth Eisner

Byleth is a wandering mercenary who possesses the mysterious Crest of Flames and can wield the powerful ancient weapon known as the Sword of the Creator. In Three Houses, they receive an offer to serve as a professor at the military academy of Garreg Mach Monastery, acting as the leader of one of its classes. Three Hopes is set in an alternative timeline where Byleth was never a professor at the academy and serves as the arch-rival of a mercenary named Shez, who seeks revenge on Byleth for slaughtering their comrades.