Byleth

Byleth is the main character of Fire Emblem: Three Houses, acting as the avatar character similar to Robin and Corrin before them. They are a professor at the Officers Academy at the Garreg Mach Monastery and are capable of wielding a variety of weapons, including their main weapon, the Sword of the Creator.

Super Smash Bros. Ultimate
Byleth was confirmed as a playable fighter in Super Smash Bros. Ultimate as the fifth and final downloadable fighter of the first Fighters Pass during a presentation on January 16, 2020, being released on January 28, 2020. Like with Robin and Corrin before them, Byleth has a male and female variant. Two of each of their color palettes refer to Dimitri and Claude for the male variant and Edelgard and Sothis for the female variant, and one other for both reference their mid-game hair color change.

All of Byleth's special moves revolve around the other legendary weapons of Three Houses. Their up special results in their sword extending into a whip, able to grab ledges and other characters similar to Joker's up special, though Byleth is able to jump off of the character, and is capable of spiking them downward if the opponent is at high enough damage. Byleth's standard special is the bow Failnaught, which acts much like Link's Bow, getting stronger the longer is it charged. Byleth's side special uses the lance Areadbhar, which is extended with a hard thrust that deals more damage at the tip, and can also be angled. Byleth's down special uses the axe Aymr, which is a strong, but slow, overhead swing attack that deals great damage to opponents, and provides Byleth with super armor. Their Final Smash is called Progenitor God Ruptured Heaven, which is an "upgraded" variant of the Ruptured Heaven skill in Three Houses, where Byleth calls upon Sothis to attack opponents. Byleth utilizes each of their weapons depending on their attacks: the Sword of the Creator for standard attack, tilt attacks, up smash, and up aerial; Failnaught for standard aerial; Areadbhar for forward smash, and forward and back aerials; and Aymr for down smash and down aerial.

By purchasing Byleth, players will also get the stage Garreg Mach Monastery, which is a transitioning stage that moves between four locations. Additional music from Three Houses is also included.

Classic Mode route
Similarly to Lucina and Young Link, Byleth's Classic Mode involves other Fire Emblem characters in the order their games of origin were released. Like with Ryu and Terry, all matches in Byleth's Classic Mode route are Stamina battles.

Palutena's Guidance
Byleth shares this stock conversation with all other DLC characters except Piranha Plant. It was originally used for Mewtwo, Lucas, Roy, Ryu, Cloud, Corrin, and Bayonetta in Super Smash Bros. for Wii U, who are downloadable fighters in that game.
 * Pit: Who is THAT?
 * Palutena: I have no data on this fighter. I can't believe it!
 * Viridi: It must be an intruder from another dimension!
 * Pit: Whoever it is, the goal remains the same: to fight and win!

Super Smash Bros. Ultimate official website

 * Byleth is coming to the Super Smash Bros. Ultimate game as a new playable fighter! This iconic fighter is the fifth fighter in the Super Smash Bros. Ultimate Fighters Pass. Using the Heroes’ Relics and the Sword of the Creator, represent the three houses and realize their full potential.

Quotes

 * "Areadbhar!"
 * "Aymr!"
 * "Failnaught!"
 * "There!"
 * "Take this!"
 * "I'll finish with this!"
 * "My battle ends here!"
 * "Let the lesson begin!"
 * "Stay focused."
 * "Try me."
 * "Each battle, a chance to grow."
 * "Allow me to demonstrate!"
 * "No hesitation!"
 * "Not my best!" (Male-exclusive)
 * "Forgive me...!" (Female-exclusive)

Trivia

 * Byleth is the first fighter in Super Smash Bros. Ultimate to debut on a Nintendo Switch game.
 * They are also the only member of the first Fighters Pass owned by Nintendo, as well as the only one from an already represented series, and the second DLC character in the game overall to be so after Piranha Plant and before Min Min.
 * Byleth is currently the only fighter in the franchise to have two taglines, largely because of both their being composed of two characters, and their technically having different names in Japan (the male Byleth being known as "Bereto" and the female Byleth being known as "Beresu").