Xehanort

Master Xehanort is the original master of Ventus, the creator and master of Vanitas, and the original incarnation of Xehanort. He is a Keyblade Master and a major character in Kingdom Hearts Birth by Sleep, shown at first in a positive light but later evolving into the main villain of the game.

Kingdom Hearts Birth by Sleep
In his youth, Xehanort, who once lived on a beach, had dreams of leaving his home in search for something greater. At some point he found a way to depart his home world and was trained to be a Keyblade Master, eventually befriending Eraqus, another Keybearer. Throughout his life, Xehanort traveled to many different worlds and obtained vast knowledge concerning Keyblade lore, the power of Light and Darkness, a detailed knowledge of the Heartless, the mysteries of the Keyblade War, and Kingdom Hearts. Realizing the power unlocking "the heart of all worlds" would grant, Xehanort set his goal on finding a way to open the door to Kingdom Hearts.

Having become an old man at that point, Master Xehanort realized he needed "a new vessel" so his knowledge would not be wasted and his goal of obtaining Kingdom Hearts could be realized. To this end he discovered Ventus and began training him to become a Keyblade wielder. Being too weak and gentle to be his Master's vessel, Master Xehanort instead used Ven to enact his ultimate plan. By shattering Ven's heart in two to create a heart of pure light (Ventus) and a heart of pure darkness (Vanitas), Master Xehanort intended to forge the X-Blade, a Keyblade capable of unlocking Kingdom Hearts.

Unfortunately the process left Ven in a comatose-like state with his broken heart of pure light slowly fading out. Master Xehanort (in a Black Coat) decided to leave Ven to die in a peaceful setting in his old home. To his master's surprise, Ventus's heart somehow survived and Xehanort realized the boy could still be of use. But Ventus was still far too weak in comparison to Vanitas, for the two needed to be equal in power for the creation of the X-Blade. Xehanort brought his former apprentice to his old friend Master Eraqus to train Ven and make him stronger.

At this point, Master Xehanort set his eyes on one of Master Eraqus's apprentices: Terra, within whom he sensed the correct potential to be his new vessel. While at the Land of Departure, Master Xehanort sabotaged the Master Qualification Exam taken by Terra and Aqua and later told him that if he were to become a true Keyblade Master, he would have to embrace the darkness in his heart rather than fight it. Shortly thereafter, Master Xehanort and Vanitas disappeared on an apparent quest to find the Princesses of Heart.

During his travels, Master Xehanort manipulated Master Eraqus's apprentices (Terra, Aqua, and Ventus), who had been sent to find him and destroy the Unversed, a malicious species created as a side-effect of Vanitas's existence. Working with Braig (who desired the Keyblade for himself), Master Xehanort staged his own capture and had Braig fight Terra, with Terra succumbing to the darkness and disfiguring Braig's face permanently. Lying that Vanitas was responsible for the whole chaos, Master Xehanort formed a pact with Terra to destroy him and took Terra under his wing, calling him by the name "Master Terra" and gaining the young man's trust.

Later on, Master Xehanort had Vanitas abduct Mickey Mouse as bait to lure Ventus to the Keyblade Graveyard, where he revealed to him the truth about his past, stating also that Master Eraqus knew about it. While Ven went to see Eraqus, Xehanort told Terra that Eraqus had gone mad and was about to destroy Ventus. Terra was tricked into defeating Master Eraqus in battle, allowing Xehanort to callously deliver the finishing blow to his former friend. Master Xehanort covered the Land of Departure in darkness, completely destroying the world and leaving nothing but the castle's remains.

Soon enough Terra, Aqua, and Ventus discovered the truth and confronted Master Xehanort and Vanitas at the Keyblade Graveyard (the remains of the legendary Keyblade War). There, Master Xehanort revealed to them his true plans as well as his intention to use Terra's body as a vessel to continue his existence long enough to see his plans of obtaining Kingdom Hearts reach fruition. In the ensuing battle, Master Xehanort froze Ventus and had Vanitas knock Aqua out cold, causing Terra to lose control of his anger and succumb again to the darkness in his heart.

Terra used the power of darkness to defeat the elderly Keyblade master, but Xehanort enacted his final scheme and used his Keyblade to unlock his own heart and transfer it into Terra's body, prolonging his life and transforming him into the new Xehanort while Master Xehanort's original body faded out with a triumphant smile.

In one of the game's final scenes, it is revealed that the hearts of Master Xehanort and Terra were (at the time) battling over internal dominance within the new Xehanort. However, with the destruction of both "Ansem" (the Heartless of Xehanort) and Xemnas (the Nobody of Xehanort) at the hands of Sora and Riku, the status of Master Xehanort is currently unknown.

Appearance
Master Xehanort appears to be an old man, bald except for thin eyebrows and a curled, silver goatee. His ears are pointed and his eyes are yellow. He has broad, hunched shoulders and a crooked back. He overall appears as a somewhat feeble old man, certainly deceiving given his absolute power.

His attire is nearly identical to the clothes that Ansem wears, namely, a white and black cloak with a red inner lining, a white shirt, black boots and white gloves. The only major difference in appearance between them is that Ansem has his chest bared, along with his emblem on the front, while Master Xehanort does not. There are a few minor changes as well - Ansem's cloak has a gold lining on the edges, while Master Xehanort's cloak has black ones. This is later carried on to Ansem, explained because this particular Heartless was made from the heart of Master Xehanort.

Master Xehanort's previous attire is briefly shown as a Black Coat, possibly as a predessesor to the attire of Organization XIII.

Master Xehanort is briefly shown when he was younger (though his face is never shown), he's seen with fairly long, mildly tanned skin, and silver hair with an interesting hairstyle (similiar to the hairstyles of Terra, Xehanort, Ansem, and Xemnas). He also wears a sleeveless black shirt and pants of the same color.

Abilities
Despite his bent and fragile appearance, Master Xehanort seems to be one of the most powerful figures to appear in the Kingdom Hearts universe and also has the ability to wield his own Keyblade, which has a black/silver finish, a spiky shaft, a head resembling the blade of a battle axe, and bears some similarities to the Oblivion Keyblade. His Keyblade also has two demonic-like eyes that were previously unique to the Soul Eater, Way to the Dawn, and his second appentice's Keyblade.

He is clearly a very powerful mage and possesses exceptional physical strength. With his magical abilities he is able to make massive columns of earth erupt from the ground and has also been shown to be able to lift hundreds of Keyblades from the ground with a powerful manipulation of wind, creating a destructive vortex which moves at his will. His ice magic not only damages on impact, but also spreads through Terra's left arm freezing it in the process. After grabbing Ventus by the head with a single hand and crushing his helmet he instantly froze his entire body although it appears to have been only externally as he was still conscious and moved his eyes.

He also displayed the ability to either teleport or move at an extreme speed as he appeared to have vanished when Ven attempted to slash him from the back. His skill with the Keyblade is also impressive. He deflected Terra's powerful strikes effortlessly and is able to wield it with either hand. He also has an as-of-yet unexplained ability involving the Keyblade where he can turn it into a ball of blue-purple energy that can be fired into the sky and apparently summons Kingdom Hearts.

His greatest and arguably deadliest ability, however, is that of using his Keyblade to transfer his heart into Terra's body and takes over him completely, combining his own powers with Terra's powers and creating the ultimate Dark Keyblade Master: Xehanort.

Personality
Much like Xehanort, "Ansem", and Xemnas, Master Xehanort is shown to be a cunning, callous, and purely evil being with the sole goal of merging with Kingdom Hearts. To this end, he is willing to put whatever he pleases on the line or destroy anything in his way, demonstrated when he manipulates several characters such as Terra, Aqua, Ventus, Braig, and even Maleficent; creates Vanitas, a sentient being for the sole purpose of forwarding his evil plan; and slays his old friend, Master Eraqus, in cold blood, after tricking Terra into defeating him in battle.

Master Xehanort is not without good points, however. His past shows that he was once a noble man who willingly took Ventus as an apprentice and cared for him until he started to lose his grip on sanity. Even after this, he still shows pity for Ventus and leaves him under Master Eraqus's care, although at the end of the game he appears to have put this behind him, shown when he freezes Ventus solid and almost kills him.

Overall, Master Xehanort is arguably the catalyst of all the events in the series so far, and could even be seen as the true villain of the Xehanort Saga. He shares most of his personality traits with Xehanort (before the latter's fight against the Lingering Sentiment and Aqua) and "Ansem", while Xemnas appears to be a fusion of Terra's characteristics and Master Xehanort's characteristics. For unknown reasons, he has a tendency to turn away from the people he speaks to, shown when he speaks to characters such as Terra, Vanitas, and Eraqus.

Fighting Style
Despite being the instigatior of the events of Kingdom Hearts Birth By Sleep, Master Xehanort only appears as a boss in Terra's story. Master Xehanort is a skilled warrior with the Keyblade even in his advanced age. He is seen casting several spells and even uses the flying Keyblades to attack.

Trivia

 * Tetsuya Nomura stated the relationship between Master Xehanort and Master Eraqus is something like old classmates.
 * Master Xehanort is voiced by Chikao Ohtuska, the real-life father of Akio Ohtsuka, the Japanese voice actor of Xehanort and Ansem (aka Xehanort's Heartless). Chikao Ohtsuka also previously voiced Captain Hook (but was replaced by Naoya Uchida for Kingdom Hearts Birth by Sleep).
 * In his youth, Master Xehanort's briefly heard voice sounds like Ryotaro Okiayu, the Japanese voice actor of Terra, possibly implying a previous connection between Master Xehanort and Terra.
 * In Kingdom Hearts Birth by Sleep, Yen Sid wonders if Master Xehanort still has "distracting thoughts". This is a sign that the two have possibly met before, as Yen Sid is revealed to be a former Keyblade Master and an acquaintance of Master Eraqus.
 * Tetsuya Nomura has confirmed in recent interviews that Xehanort will return in future installments and that Kingdom Hearts III will feature his final battle against Sora, but it is currently unknown if he will return as Master Xehanort or in his younger incarnation (Xehanort).