Byleth Eisner Sirius, or simply put, Byleth, is a character in Nintendo's Fire Emblem franchise. They first appeared as the player character and main protagonist of Fire Emblem: Three Houses (2019), and have since appeared as a playable character in the crossover games Super Smash Bros. Ultimate (2018) and Fire Emblem Heroes (2017), being added as a DLC in 2020 and 2021 respectively, and as a recurring antagonist of Fire Emblem Warriors: Three Hopes (2022). In each game, players can choose between a female or male version of the character.