Vanitas

Vanitas is an Unversed and one of the primary antagonists in Kingdom Hearts Birth by Sleep. He is the apprentice of Master Xehanort. Created by Master Xehanort, Vanitas is the embodiment of the extracted darkness from Ventus's heart. Vanitas's birth sparked the threat of the rest of the Unversed.

Kingdom Hearts Birth by Sleep
''A mysterious figure with ties to Master Xehanort. He warned Ventus that Terra was in some kind of danger, but disappeared before explaining any further.''

Kingdom Hearts Birth by Sleep
Four years before the events of Kingdom Hearts Birth by Sleep, Ventus served as Master Xehanort's apprentice. The Keyblade wielder was sent to the Keyblade Graveyard, where he was forced by his master to face several Heartless. Ventus lost the battle, and was knocked unconscious. Master Xehanort then proceeded to use his Keyblade to unlock Ventus's heart, extracting the darkness within and resulting in an orb of dark energy forming into a human who then assumes the name "Vanitas". The dark enigma is also the source of the Unversed, as well as a key component in Master Xehanort's plans.

After Master Xehanort views the battle between Terra and Aqua as part of their Mark of Mastery, he leaves the room to find a hidden Vanitas awaiting him. The two converse about Ventus, and Vanitas claims that Ventus's performance was weak, and he still needs to "break that loser in." Master Xehanort tells him to do so somewhere else as he needed to keep up appearances. So Vanitas decides to set him off on a journey. Vanitas later appears before Ventus in his room, speaking of Terra being a different person, and that Ventus should follow him to see it. Ventus denies his dark half's claims, saying that he and Terra will always be friends. Vanitas simply mocks his friendship with Terra, telling him to grow up and vanishes into a corridor of darkness, claiming that unless Ventus sees it for himself and looks beyond his "own little world", he will not know the truth.

After his first few ventures throughout the worlds, Ventus spots Vanitas in space and is lured to the Keyblade Graveyard. Vanitas approaches him, speaks of Terra losing his identity again, and challenges him to a duel, intent on testing his power and revealing for the first time he is a Keyblade wielder. Vanitas gains the upper hand mid-way, knocking Ventus down. Vanitas then prepares to eliminate Ventus for being at such a low level of power, deeming the boy too worthless to be of use, but before he could do so, Mickey Mouse appears, healing Ventus. Mickey Mouse and Ventus then proceed to fight Vanitas, who simply shrugs off the fight and leaves yet again upon his defeat, claiming that Ventus is on "probation".

After the battle against the Trinity Armor in Radiant Garden, Vanitas appears to Aqua and approaches her, taunting her by inquiring about Ventus and if he has gotten stronger. When Aqua asks what he means, Vanitas attacks, the two fighting a vicious battle. After the duel, Aqua attempts to remove Vanitas's helmet, but the dark enigma startles her with an insane laugh. He then compliments her skill, making an ambiguous comment about her being his backup plan, revealing that it was all a ruse to test her strength. Ventus overhears Vanitas's last few words to Aqua, returning to her side just as he leaves in another corridor of darkness.

While in Neverland, Vanitas encounters and kidnaps Mickey Mouse on Master Xehanort's orders. Though the fight is not shown, it is clear Vanitas won. The villain later crosses paths with Aqua again, this time with Ventus's cherished Wooden Keyblade. Vanitas cruelly mocks Aqua's actions and snaps the toy weapon in two, claiming that Ventus has outgrown the toy. Vanitas also claims that he has has outgrown his need for Aqua as a backup plan, and then battles her once again, but is soundly defeated and knocked out cold. The battle leaves Aqua exhausted and enraged at the thought of Ventus being in danger, and Vanitas then disappears through a corridor of darkness.

Vanitas encounters Ventus again in Destiny Islands, after the latter is thrown through a portal summoned by Terra. Vanitas tells him that since they are equal in power, they can fuse together to create the χ-blade. Ventus refuses, claiming that the χ-blade cannot be created if he does not fight. Vanitas, though slightly angered, remains unfazed. Then, in a series of flashbacks, Vanitas explains his birth from the darkness in Ventus's heart, and how he took his place as Master Xehanort's apprentice. This causes Ventus great pain in regaining his memories, while Vanitas vanished as Ventus fled the world. However, Vanitas quickly invited Ventus to the Keyblade Graveyard, where he threatens to "choke the life out of Terra and Aqua", and callously wonders how long Ventus will "play the pacifist."

When Terra, Ventus, and Aqua approach their final battle with Vanitas and Master Xehanort at the Keyblade Graveyard, intense battles ensue. The two villains meet up with the trio, and after a few heated words, Terra quickly charges towards them. Master Xehanort intervenes, however, blocking Terra's path with massive rock formations. As Terra continues to pursue Master Xehanort, Vanitas goes after Aqua and Ventus. The two fight valiantly against the dark apprentice, but not before Vanitas returns to Master Xehanort's side after Ventus is frozen. He battles Terra alongside Master Xehanort, who later commands Vanitas to go after Ventus and Aqua again.

Vanitas attacks Aqua from above, knocking her unconscious, and prepares the final blow to eliminate her while Ventus lies helpless and frozen. Ventus summons all of his willpower, however, and breaks out of the ice to face Vanitas in battle, defeating him once again. Vanitas compliments Ventus on his skill and finally reveals his face, explaining himself to be the source of all Unversed. Vanitas proudly explains that his plan was to spread the Unversed across the worlds, so Ventus could go on a journey and grow strong enough to form the χ-blade. While explaining this, Vanitas summons several Flood Unversed to restrain Ventus as he forcefully integrates into him. In a burst of light, Vanitas and Ventus are transported to the Dive to the Heart. Ventus's pillar now hosts a picture of Vanitas alongside his own. Vanitas wields an incomplete version of the χ-blade.

Vanitas claims their fusion was incomplete, and they only managed to make a fraction of the χ-blade. He then tries to fuse with Ventus once again, but Ventus refuses, vowing to defeat Vanitas and destroy the χ-blade. The dark apprentice simply laughs, confident in the fact that they both know that if the χ-blade is destroyed, so will be Ventus's heart. However, Ventus rebukes him, saying he will fight for his friends no matter what, even if the price is his heart, despite Vanitas's mocking of his reason to fight. The two Keyblade wielders then begin a final battle in the Dive to the Heart.

As Ventus battles Vanitas in their Awakening, Aqua and Mickey are forced in the Keyblade Graveyard to battle a sort of Ventus-Vanitas fusion, which is Ventus's form with Vanitas's golden eyes and bodysuit. Ventus-Vanitas summons the completed χ-blade, and exclaims with psychotic glee that he plans to unlock Kingdom Hearts so the worlds can be connected and the legendary Keyblade War can begin again, and attacks the duo. As Aqua defeats her possessed friend and destroys the χ-blade, Vanitas's metaphysical battle with Ventus comes to an end after he shatters the pillar on which they were fighting. Vanitas fades out of existence, taking all Unversed in existence with him and relinquishing his control over Ventus. Unfortunately, the victory is bittersweet, as Ventus loses his heart and falls into a coma in the process.

Appearance
Vanitas wears a black and red organic-looking bodysuit, which is quite similar to Riku's Dark Mode from Kingdom Hearts and Kingdom Hearts: Chain of Memories. He wears a silver helmet covered with dark glass, hiding his face from view. Just before he possesses Ventus, he unmasks himself, revealing that he looks identical to Sora, although he possesses golden-yellow eyes, black hair, and paler skin. In an interview with Tetsuya Nomura, it is revealed that this similarity is due to Sora's heart connecting with Ventus near the beginning of the game, and had anyone else connected with Ventus's heart, Vanitas would look like that person. Additionally, his voice is identical to that of the fifteen-year-old Sora, but at a much darker and more sinister pitch.

His appearance before Ventus's connection with Sora has yet to be revealed. He normally wields a Keyblade that is colored primarily in red and black, with two blue eyes like the Soul Eater, Way to the Dawn, Chaos Reaper, and Master Xehanort's Keyblade, but in the final chapters, he gains the χ-blade, and when he fuses with Ventus, he also alters Ventus' body to accommodate his yellow eyes and bodysuit.

Personality
As a being created from the purest of darkness, Vanitas is proud, cunning, cruel, and pure evil. The lives of others, including that of even Master Xehanort, hold absolutely no value to him, he shows no remorse for his actions, and as a pragmatist, he will strike without a moment's thought or warning, as seen when he ambushes Aqua in the Keyblade Graveyard and attempts to eliminate her. Despite his loyalty to Master Xehanort, he has disregarded his orders on occasion; for example, he attempts to eliminate Ventus after defeating him in their first battle despite full knowledge that Master Xehanort needed Ventus alive for his plans, and even fought Aqua to test her for a possible "back-up plan." He is also shown to be uncaring, having no sympathy for anyone but himself, in addition to frequently criticizing Ventus' friendships with Terra and Aqua and constantly referring to Ventus as an "idiot." He can also be overconfident at times; when fighting Aqua for the final time, Vanitas boasts that nothing Aqua tries will be able to stop him. His overall personality is in an extremely stark contrast to Ventus and Sora, as well as their extensions Roxas and Xion, who are valiant, value friendship, and possess heroic qualities.

Vanitas also appears to be somewhat insane, judging by what has been shown in-game. The most prominent examples include his bursts of maniacal laughter when Aqua tried to unmask him and when Ven declared he would defeat him and destroy the χ-blade, and his explanation to Aqua and Mickey about what he plans to do with the χ-blade and Kingdom Hearts after possessing Ventus, the latter of which he does with a crazed smile on his face.

Abilities
Vanitas is, to say the least, a skilled and extremely aggressive opponent, showing a mastery in both dark magic and wielding the Keyblade. He is swift and agile, able to perform complicated and nearly impossible acrobatic feats such as jumping off of a high cliff while still landing on his feet, and even riding a cloud of flying Keyblades, as well as teleporting behind opponents at high speeds to launch attacks. Able to combine physical combos with magic, he appears to have superhuman endurance, surviving each of his battles while taking little to no bodily damage. Vanitas also seems to possess superhuman strength; while possessing Ventus, he is able to shatter Ventus's metaphysical Awakening pillar with a single strike and create a gust of wind powerful enough to send Aqua and Mickey flying with a single swing of his arm. It is most likely that these actions were made possible only through the χ-blade, which Vanitas wielded on both occasions. Vanitas is also a difficult opponent to fight in close combat, as he can quickly counterattack if struck multiple times, making him very dangerous. He also demonstrates the ability to levitate.

While Vanitas acts based on his own desires, it appears that Master Xehanort can summon him at will. Vanitas's arguably most dangerous and destructive ability, however, is the power to create and control the Unversed. As he was born from the purest form of darkness, Vanitas can manipulate negative emotions and spawn them as Unversed. All defeated sentiments return to him, able to be summoned again if needed.

Weapon
Vanitas wields a very unique Keyblade known as the Void Gear, and has a battle pose that is very similar to Riku's stance. The Keyblade can be summoned at will, appearing in Vanitas's hand in a flash of purple flame. Vanitas's Lingering Spirit‎ also wields a monochrome version of this Keyblade.

When fused with Ventus, Vanitas gains the ability to wield the most powerful Keyblade of all, the χ-blade. This weapon multiplies his initial strength and attack range a great deal. Vanitas shows great skill in wielding both the incomplete and finalized versions of the χ-blade, able to perform strong combos and powerful desperation moves.

Trivia

 * After his first spoken line, Nomura made a joke saying that he was to voice Vanitas. Nomura also stated in another interview that Vanitas's identity was familiar and perhaps also shocking. It was later revealed that Vanitas was voiced by Miyu Irino, the Japanese voice actor for Sora. According to Tetsuya Nomura, Irino had said for a while that he wanted to play an evil character, and Nomura jokingly stated he sort of got carried away with it.
 * Vanitas's name is derived from the Latin word for "Vanity" or "Emptiness", and was chosen for its meaning, that it sounded similar to "Ventus", and that it was a written pun on "Sora" in Japanese.
 * The Kingdom Hearts Birth by Sleep Ultimania refers to Vanitas as the Masked Youth (仮面の少年).
 * Out of all the antagonists to appear in the series, Vanitas has been fought in the most boss battles, a total of seven battles in all.