Byleth is the main protagonist of Fire Emblem: Three Houses. 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.

== Appearance == This character card focuses on the male counterpart of Byleth. He's 21 years old, stands at 5'9'' (175 cm), and weighs 160 lbs (73 kg). He is characterized by his fair skin, striking teal or aquamarine hair that is styled in a somewhat disheveled yet distinct manner, and intense blue eyes.

Complementing these features, he wears a distinctive outfit that combines practical battle attire with elements of a teacher's uniform. He is typically depicted in a long, flowing black coat with a high collar and wide sleeves, often draped over his shoulders like a cape. Beneath the coat, he wears a dark, fitted top that appears to be made of some kind of armor or reinforced material, with metallic shoulder pads and a chest plate providing protection.

His lower body is clad in dark trousers and tall, sturdy black boots that reach up to his knees, often featuring some armored detailing around the shins. A prominent feature of his ensemble is a belt with a large, ornate buckle, from which hang various pouches or adornments. He also wears black gloves.

The overall aesthetic is one of a disciplined and formidable warrior, befitting his role as both a mercenary and a professor.

== Personality == From a young age, Byleth has shown minimal emotional expressions, with minor changes in their visage when reacting emotionally. As a newborn, Jeralt observed that they neither laughed nor cried. This stoicism is consistent in their dialogue, appearing straightforward and calm. Allies are often surprised when they smile, attributed by Alois to their resemblance to Jeralt, who shows similar calmness. Jeralt, however, sees Byleth as more like their mother Sitri, who also had difficulty expressing emotions. Close observers like Jeralt notice subtle emotional shifts.

Over time at the Academy, Byleth becomes more expressive, influenced by bonds with students. Despite seeming indifferent, they are perceptive and supportive. As events unfold, their emotions grow more varied, including sorrow, vengeance, and happiness. Sheltered by Jeralt from some world knowledge, they become curious about the Church of Seiros, Crests, and regional politics.

In the early years in Jeralt's mercenary group, Byleth earned the nickname 'Ashen Demon' for their emotionless combat style, a sensitive subject for them. Early game, Sothis refuses to progress unless the player acknowledges their humanity, indicating discomfort with the dehumanizing nickname.

The house leaders respect Byleth’s martial skill and continue to call them teacher, regretfully wishing they had chosen their house if not teaching theirs. Both genders of Byleth in Heroes are unsure of friendship versus alliance, but are liked broadly. Their wisdom influences the outcome of Three Houses, guiding students and affecting alliances, some switching to their house or joining their cause—even defectors from enemy nations—altering their fate. Those not joining often regret facing them, with some in Crimson Flower vowing revenge.

In Cindered Shadows and Three Hopes, Byleth enjoys helping, listening, and values their father, swords, allies, smiles, and trust, with no clear dislikes. They detest senseless killing and vow to avenge harm against their father.

== Trivia ==

• Byleth's default name in Japanese differs slightly between genders, as a male Byleth is spelled "ベレト" (Bereto), while the female is "ベレス" (Beresu).
• While the player chooses Byleth's birthday, the default birthdate is 20th of the Horsebow Moon 1159 (September 20), a significant date in the story and reinforced by information from Jeralt's journal. This, as a result, makes Byleth a Virgo.
• Byleth is the first Avatar character to have a defined difference in height between genders.
• Byleth, unlike other playable characters in Three Houses, possesses a unique color palette for all of their available classes instead of sharing a palette with another character, primarily blackish-blue with purple accents.
• Byleth was implied to be 20/21, but with the Cindered Shadows story released, it's been confirmed that they're indeed of said age by Sitri's date of death, which has been added on her grave.
• Byleth is one of the only 3 characters in Three Houses to align to 3 different factions in a single playthrough (and the only one to consistently do so), the other being Ashe on Verdant Wind/Silver Snow routes, and Lorenz on Azure Moon/Silver Snow routes, if recruited.
• The number thirteen seems to be a recurring theme for Byleth. Byleth is the thirteenth host of Sothis. The demon of Byleth's namesake, Beleth, is the thirteenth demon listed in "The Lesser Key of Solomon". Byleth starts with a base Strength of thirteen in both Heroes and Three Houses. Byleth is the thirteenth newcomer to Super Smash Bros. Ultimate. The maximum amount of Divine Pulse charges Byleth can use in Three Houses is also thirteen.
• In Three Hopes, Byleth has the most extremely skewed favorite/disliked food ratio between all units, liking 28 of the 32 dishes available and disliking 0.

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