Xion

Xion is the fourteenth member of Organization XIII, first appearing in the game Kingdom Hearts 358/2 Days. She is not actually a Nobody, but an imperfect clone of Sora created from his leaked memories by Xemnas as a fail-safe in case Sora proved to be useless to Organization XIII's plans. As Sora's memories are the basis of her being, Xion resembles Kairi, who is Sora's strongest memory. Like Sora and Roxas, Xion can wield a Keyblade, the Kingdom Key, leading to a brief confrontation with Riku who questions why she can wield the Keyblade, and whether or not it is real.

During her time in the Organization, Xion closely befriends Roxas and Axel, but she eventually leaves the Organization as she develops more of Sora's traits in conjunction to Naminé's attempt of restoring Sora's memories. Eventually desiring to be the real person, not caring if Sora ever awakens, Xion came to the conclusion that she would become whole if she absorbed Roxas, Sora's Nobody, and attacked him. However, Roxas absorbed her instead, gaining use of her Keyblade which results in his signature fighting style.

Kingdom Hearts 358/2 Days
Xion is first introduced in the game on the seventh day with her hood up. After Axel is sent away to Castle Oblivion, Xion and Roxas are sent on missions together. Xion opens up to Roxas, first revealing her face to him, and on one of their missions, they discover that Xion can use the Keyblade. After some time, Roxas and Xion begin eating ice cream together on top of the Clock Tower, and they begin to bond. Later, on one of their missions at Beast Castle, Xion says she cannot summon the Kingdom Key on her own, so Roxas let's her borrow his. After defeating the enemy, Xion gives Roxas back his Keyblade saying she no longer needs it, and then has the ability to summon the Keyblade on her own.

One day Xion goes missing, and then we see her the next day crying on her bed. We are then shown a brief flashback of her fight against Riku. The next day Xion avoids Roxas and does not go to the clock tower. The next day Roxas has a mission in Twilight Town and sees Xion on top of the clock tower. He goes up to talk to her but she seems depressed by something. Roxas says that they should complete the mission together,she agrees. After the mission they go back to the clock tower for more ice-cream. Xion finally has a full flash back on her fight against Riku.

Fighting Style
As a replica of Sora, she can wield the keyblade and her fighting style greatly resembles his original Kingdom Hearts incarnation. However her style is more similar to Roxas. Like Roxas she thrusts with one hand and her finisher resembles the Vortex ability. She and Roxas can apparently share keychains with each other, allowing them to use the same keyblades.

Trivia

 * Xion is the fourth female boss to have appeared in the series and the second to undergo transformations.

Xion