Lucina

Lucina is a character from the Fire Emblem series. She was confirmed to be a playable character in Super Smash Bros. for Nintendo 3DS / Wii U in the same character reveal trailer as Robin, another Fire Emblem representative. She is Chrom's future daughter that made her debut in Fire Emblem: Awakening. She has the same moves as Marth, but has slightly altered characteristics, such as shorter height and attacks that don't concentrate at the tip of her sword. Lucina's palette swaps are based on other female characters in the Fire Emblem series.

Lucina was originally considered to be an alternative costume to Marth, much like Alph is to Captain Olimar, but ultimately, Super Smash Bros. director Masahiro Sakurai decided to make her a separate character. The reasoning for this is that he wanted some of her attacks to be significantly different to Marth's.

Lucina is an unlockable character in both versions of Super Smash Bros. for Nintendo 3DS / Wii U. To unlock her in the Nintendo 3DS version, the player must either complete Classic Mode as Marth without the use of continues or play 40 matches, then defeat her in a 1-stock match on the Arena Ferox stage. In the Wii U version, the player can unlock her by completing Classic Mode on Intensity 5.5 or higher or by playing 30 matches, then defeating her in a 1-stock match on the Coliseum stage.

On a side note, Lucina is the only unlockable character that was announced before the Japanese release of the Nintendo 3DS version.

Trivia

 * Lucina is the first (and currently only) female unlockable character in the Smash Bros. series, being unlockable in both versions of Super Smash Bros. for Nintendo 3DS / Wii U; on the contrary, all of the other unlockable characters, in addition to the ones from the previous three games, are male and gender-neutral (latter referring to Pokemon).