Vanitas

"It happened when you and I were split into two. The negativity took shape as these monsters. They are what I feel-a horde of fledgling emotions under my control. I released them into all the worlds I could, hoping to lure you away from home and isolate you from your master. We needed to make you stronger. The Unversed were the perfect opponents. And better yet, no matter how many times you defeat them, their negativity flows right back into me. You never stood a chance against us, Ventus."

- Vanitas

Vanitas is one of the main antagonists of the Kingdom Hearts series. He is Ventus's dark half and Master Xehanort's apprentice.

Birth By Sleep novels
In the novels, Vanitas's life between his creation and the events of Kingdom Hearts Birth by Sleep is expanded upon. At first, Vanitas was a faceless being much like a Heartless but with red eyes, that felt sad for his separation from Ventus. However, that sadness soon turned to hate and contempt for what he considered his weakness. In a way, Vanitas hated himself for being so weak. Vanitas was well aware of his existence, and soon started questioning why he was born, and every time he felt something, an Unversed would come to be. This caused him to be irritated by the fact that such a monster was born from him, so he destroyed the Unversed with his Keyblade without any hesitation; but every time he destroyed an Unversed, he himself would feel strong physical pain running through his body, and after the Unversed was destroyed, the pain and negative feeling would return to Vanitas's mind, which added more to the irritation he was feeling and in turn another Unversed of "irritation" would be born from him. When a newborn's heart came in contact with Ventus's fractured heart, he also directly contacted Vanitas's heart. After feeling a sharp pain in his chest, Vanitas's body fell to the ground of the wasteland near the Keyblade Graveyard and almost lost his consciousness, feeling being engulfed by absolute Darkness. That was when Vanitas heard Sora's voice and then he saw Light. The Light eventually surrounded his whole body. He then heard a voice saying, "Let's open the door". Vanitas then opened his eyes and found out that now he had a normal boy's face. He also realized that someone, probably also a newborn heart like himself, had saved Ventus's heart from completely fading away. Because Vanitas told Master Xehanort that if he kept both him and Ventus, he couldn't guarantee that he could keep Ventus alive, since he found it was hard to suppress his impulse to hurt Ventus, Xehanort had to take Ventus to the Land of Departure, asking Eraqus to take care of the boy. But after Ventus left, Vanitas started to miss him, and he kept wondering why they got separated from each other. This caused him to feel miserable and immense pain. At the same time, he also felt very lost and anxious about his future; without Ventus, what would become of him? What was he supposed to do? What was the meaning of his existence? Why did he feel so suffocated in his chest? The more he thought about these questions, the more anxious, irritated, and lonely he felt. And the more he felt that, the more Unversed were created. Looking at the Unversed was like looking at his own weakness that he did not want to admit, so he started to kill them in a cycle of suffering that he could not escape. At the same time, Master Xehanort could only coldly watch Vanitas harming himself from far away. Vanitas desperately wanted to escape from this vicious cycle of pain and suffering. But as young as he was at that time, he simply didn't know any other ways other than killing the Unversed. Until the point the pain was too much to endure, he finally collapsed onto the ground of Keyblade Graveyard, and cried. Tears started running down his face silently as he lay on the ground, alone. Master Xehanort came to him, telling him the only way for him to achieve salvation was to become the χ-blade. Becoming the χ-blade was the only way for him to truly unite with Ventus again, and the χ-blade would bring salvation not only to him but also to the whole world. Vanitas desperately wanted to free himself from this unbearable fate, thus to become the χ-blade had now become his goal, his whole life purpose, and his only Light of Hope to lead him out of this Darkness.

Birth By Sleep
As Ventus-Vanitas, Vanitas was found by Xehanort and became his apprentice, Xehanort decided to use him to create the χ-blade and also as a vessel, he found that Ventus could not be a vessel but could still make the χ-blade. Xehanort gets Ventus to fight against a horde of Neoshadows but Ventus is defeated so Xehanort splits him into two beings, Ventus-heart of pure light and Vanitas-heart of pure darkness.

After Ven's training, Vanitas arrives and taunts him about being weak before leaving and telling him that if he does not chase Terra, he will never see him again. Vanitas later met Ven at the Badlands and attempted to kill him, thinking he was too weak but Mickey saved him and Vanitas left.

Vanitas later encountered Aqua at the Radiant Garden and they fought, but Vanitas left, revealing that it was just a test. Vanitas met Aqua again in Neverland and fought her because he no longer needed her. After the battle she faints and he leaves, it is unknown why he did not finish her off.

Vanitas confronts Ventus and forces him to go to the Keyblade Graveyard after revealing their past.

Vanitas then fights against Aqua and Ventus at the Keyblade Graveyard and then he faces Terra with Xehanort's help, though he lives midway through the fight so he can forge the χ-blade. Vanitas knocks Aqua out and is about to finish her but Ventus recovers and fights Vanitas.

In the end, while confronting Ven, Vanitas takes his mask off, revealing his face to be look like Sora, minus the black hair and gold eyes. He reveals the Unversed came from him, and then would return to him once they're defeated.

During the final confrontion, Vanitas forces Ventus to fuse with him to become Ventus-Vanitas, Ventus fights Vanitas inside his mind, while Aqua and Mickey face off against Vanitas controlling Ventus. After a long fight, Aqua and Mickey defeat Ventus-Vanitas and Ventus defeats Vanitas in their mental battle.

During Aqua's search for Terra, she senses a strong presence in the Keyblade Graveyard, arriving there she is confronted by Vanitas' Lingering Spirit who attacks her, she knows he has all of his old powers plus the Unversed's powers and the χ-blade. After a long battle, Aqua defeats him and continues her search for Terra.

Pre-Kingdom Hearts
Vanitas' Heart latched onto Sora at the same time as Ventus' Heart did.

Dream Drop Distance
In Dream Drop Distance, Vanitas appears to confront Sora inside the Cathedral alongside Xehanort as his heart is no longer fully inside Sora. He later appears in the World that Never Was when Sora is trapped in a Nightmare. He comes out of Sora in the form of Anti Black Coat and confronts Riku when he attempts to save Sora from being possesed. Later after Xehanort manages to damage Sora's heart, Riku is forced to dive into Sora's heart, Vanitas notices him and attacks in the form of many AntiSoras, when Riku finally reaches Sora's heart, Vanitas confronts Riku as Nightmare Sora but is defeated.