Master Xehanort

Master Xehanort is a Keyblade Master, the first master of Ventus, and the creator and master of Vanitas, the original incarnation of Ansem and Xemnas (partially) and a counterpart of Young Xehanort. He serves as the main antagonist of Kingdom Hearts Birth by Sleep and the primary main antagonist of Kingdom Hearts 3D: Dream Drop Distance.

He is the main antagonist of the "Xehanort Saga", the first part of the Kingdom Hearts series.

Kingdom Hearts Birth by Sleep
''One of the true Keyblade Masters and a longtime acquaintance of Master Eraqus. He is connected with the masked boy, and harbors a hidden agenda.''

Unlike Master Eraqus, Xehanort believes darkness need not be rejected if it can be controlled.

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, whom he began to see as a younger brother. 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.

Throughout his travels, Xehanort saw that light was much more prevalent and believed that the darkness needed to be amplified to make a perfect balance. Seeing that light is becoming too prevalent while darkness is being excluded, Xehanort makes his plans to destroy the current system of light through another Keyblade War and reorganize the worlds into a more balanced existence through the great darkness.

After years of researching the Keyblade War, Xehanort becomes obsessed with unlocking all it's secrets and understanding just how the world was made through such a conflict. Knowing that the world was made from the great darkness of the war, Xehanort believes that another war would be the perfect way to recreate the universe into a more ideal one. Realizing the power unlocking the "heart of all worlds" would grant, Xehanort sets his goal on finding a way to open the door to Kingdom Hearts and incite another Keyblade War to find the answers he has been looking for and recreate the worlds.

He eventually discovered a way of doing so: forging the χ-blade, a legendary Keyblade capable of unlocking Kingdom Hearts and cause of the Keyblade War. One day, when he discussed his plans to forge the χ-blade with Master Eraqus, he was met with opposition from the latter, who insisted that his plan was too dangerous. This discussion quickly escalated into physical violence, which ended when Xehanort used the powers of darkness to scar Eraqus's face.

By this time, Master Xehanort had grown old, and realized that he must transfer his essence and knowledge to a "new vessel" in order to survive to see his plans reach fruition. To accomplish this, he sought out an apprentice and found the boy Ventus, who he began training as a Keyblade wielder with the intent of pitting him against one of Master Eraqus's students of light, forging the χ-blade, and to eventually use him as his vessel.

However, Ventus proved to be a poor candidate, and when he refused to use his darkness to fight several Heartless, Master Xehanort instead decided to use him as part of his ultimate plan: using his Keyblade, Master Xehanort extracted the darkness from Ventus's heart, forming a sentient being of pure darkness to whom Master Xehanort gave the name "Vanitas." With these two boys, Master Xehanort intended to forge the χ-blade.

Unfortunately, the process left Ven in a comatose state with his broken heart of pure light slowly fading out. Master Xehanort (in a Black Coat) decided to leave Ven to live out his last days peacefully in his old home, the Destiny Islands. To his master's surprise, Ventus's heart somehow survived and Xehanort realized the boy could still be of use. However, Ventus was still far too weak in comparison to Vanitas, for the two needed to be equal in power for the creation of the χ-blade.

Additionally, Xehanort realized that he could not train Ventus and Vanitas together, as Vanitas's darkness would eventually consume and completely destroy Ventus's light. Master Xehanort ultimately left Ventus in Eraqus's care, to let him train and grow 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 in the Land of Departure, Master Xehanort sabotages the Mark of Mastery Exam taken by Terra and Aqua, causing Terra to fail, and later tells him that if he were to become a true Keyblade Master, he would have to embrace the darkness in his heart and channel it rather than fight it. Shortly thereafter, Master Xehanort and Vanitas disappear on an apparent quest to find the Princesses of Heart.

During his travels, Master Xehanort manipulates 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, and at the same time, comes into contact with and also manipulates the evil fairy, Maleficent, into beginning a quest to capture the seven Princesses as part of an elaborate fail safe.

He encounters Terra in the Keyblade Graveyard and puts his manipulative skills to the test, explaining the reason for his actions: He is trying to safeguard the light from the "demon" he unleashed. He then tells Terra an altered version of Vanitas's origins: supposedly, Vanitas was created when Ventus was overtaken by his darkness and Master Xehanort extracted Ventus's darkness in a desperate attempt to save him, severely damaging Ventus's heart in the process. Ashamed, Xehanort left Ventus in Master Eraqus's care.

Though he had attempted to keep Vanitas contained, the dark enigma escaped and began spreading the Unversed throughout the worlds. Master Xehanort then asked Terra to help him stop Vanitas and atone for his mistake. Terra agrees, and is instructed to search in the Radiant Garden, where Vanitas will undoubtedly strike next.

He next travels to the Radiant Garden and strikes a bargain with Braig, who desires the Keyblade for himself. Afterwards, Master Xehanort stages his own capture and has Braig fight Terra, with Terra succumbing to the darkness and injuring Braig, blinding the young man in the right eye and scarring his face. Master Xehanort tells Terra that he shows the true Mark of Mastery, as he was able to channel the darkness instead of rejecting it, and that Eraqus will never accept it out of his fear of darkness.

He then goes on to state his belief that light and darkness are a balance that must always be maintained. He then gives Terra an opportunity to be his pupil, claiming that they can do the worlds much greater good by wielding light and darkness in equal shares. Master Xehanort then pulls the final string, calling him by the name "Master Terra" and gaining the young man's trust.

Later on, Master Xehanort has Vanitas abduct Mickey Mouse as bait to lure Ventus to the Keyblade Graveyard, where he reveals to him the truth about his past, also stating that Master Eraqus knows about it. While Ven goes to see Eraqus, Xehanort tells Terra that Ventus went to see Eraqus about his past, and is worried he may force the truth out of him. He also tells him that Eraqus has gone mad and is about to destroy Ventus. Terra is tricked into defeating Master Eraqus in battle, allowing Xehanort to cruelly deliver the finishing blow to his former friend.

Master Xehanort then tells Terra to go to the Keyblade Graveyard where he will see Aqua and Ventus for the last time before falling prey to the darkness. He then covers the Land of Departure in darkness, completely destroying the world and leaving nothing but the castle's remains, telling Terra he would not need a home where he is going.

Soon enough Terra, Aqua, and Ventus discover the truth and confront Master Xehanort and Vanitas at the Keyblade Graveyard (the remains of the legendary Keyblade War). There, Master Xehanort reveals to them his true plans to create the χ-blade and unlock Kingdom Hearts. In the ensuing battle, Master Xehanort freezes Ventus, and when Terra reaches Master Xehanort, he demands to know what really happened to Ventus's heart.

Master Xehanort gladly reveals that he intentionally shattered Ventus's heart and created Vanitas. Terra becomes enraged, and battles Xehanort and Vanitas. Mid-way in the fight, Master Xehanort commands Vanitas to fuse with Ventus and kill Aqua.

Terra tries to stop Vanitas, but is impeded by Master Xehanort, who gleefully tells Terra that he is powerless to save them, and that he should use his rage and despair to empower himself. Terra, enraged that Xehanort would destroy his "father" Eraqus and go after his friends, loses control of his anger and succumbs again to the darkness in his heart.

Terra uses the power of darkness to defeat the elderly Keyblade master, but Xehanort enacts his final scheme and uses his Keyblade to unlock his own heart and transfer it into Terra's body, prolonging Xehanort's life and transforming Terra into Terra-Xehanort, while Master Xehanort's original body fades out of existence with a triumphant smile.

Blank Points
The hearts of Master Xehanort and Terra are shown disputing over internal dominance within the amnesic Xehanort. Despite Master Xehanort's insistence that he will soon incorporate Terra's heart into his own, Terra remains confident that he will win over and eventually expel Master Xehanort, who realizes that Terra is harboring the heart of Master Eraqus. Despite this, Master Xehanort shows no concern and reveals to Terra that possessing him was merely one of many roads he chose to take.

Signs of What's Next
In Kingdom Hearts Re:coded, Yen Sid explains that the destruction of "Ansem" and Xemnas will eventually lead to the reconstruction of Master Xehanort.

A fragmentary passage
A young Master Xehanort is shown as the first incarnation before both "Ansem" and Xemnas, and appears in his elderly form after them.

Kingdom Hearts 3D: Dream Drop Distance
With Master Xehanort's impending return drawing closer and closer, Yen Sid finally reveals the truth behind Xehanort to Sora and Riku as he tasks them with the mission to awaken seven different worlds from a state of sleep. However, as Sora and Riku go through these worlds deep within the Realm of Sleep, they are intercepted by various incarnations of Xehanort, including Xehanort's Heartless, Xemnas, and a former Young Xehanort of the Keyblade Master.

It is eventually revealed by Braig, who has also returned due to his Heartless and Nobody being defeated, that Master Xehanort has enlisted the help of his younger self from an alternate timeline, who was given powers to survey time and space itself to enlist different incarnations of himself, including Xehanort's Heartless and Xemnas, to form a new Organization XIII.

With these various forms of himself under his control, Xehanort uses them to draw Sora deeper into the worlds of sleep to use him as a vessel to complete the new Organization. Riku and Mickey are able to locate a comatose Sora in the Organization's former headquarters in the World that Never Was, now under the control of Master Xehanort, and face his younger self, infused with his future self's power to wield a keyblade, in battle to save him. When they defeat him, the final remnants of Master Xehanort's consciousness leave his younger self and combine to form the original, elderly Master Xehanort, finally returned to full power.

Upon Master Xehanort's return, the villain reveals that he has not given up on his plans to form the χ-Blade and incite another Keyblade War. In fact, he further states that everything that has occurred throughout the past twelve years, from Maleficent capturing the Princesses of Heart, to the formation of Organization XIII, was all part of an insidious, fail-safe plot to form the χ-Blade.

Xehanort explains to Riku and King Mickey how his plans to merge Ventus and Vanitas were an overly hasty attempt to form the χ-Blade, and that he overlooked the true way to create the weapon; by clashing thirteen hearts of darkness against the seven defending lights of the worlds. It is revealed that in the aftermath of the Keyblade War, the χ-Blade was shattered, and released seven lights and thirteen darkness's, and when the two sets of light and darkness are brought together, the true χ-Blade would return.

Over a decade ago, Xehanort enlisted the help of Braig, who desired the power of the Keyblade for himself, to form Organization XIII in order to gather thirteen strong beings to fill with fragments of darkness and Xehanort's heart to make them all clones of him, and use them to fight the seven Keyblade defenders of the worlds to recreate the χ-Blade. Braig was the first of these planned clones, which was why his appearance changed&mdash;he had a yellow eye and pointed ears&mdash;due to him agreeing with Xehanort's plans; he would be able to share in Xehanort's power and wield the Keyblade once a full clone, though he would slowly lose his will and mind to Xehanort, in exchange.

To further these plans, Xehanort, possessing Terra's body, and Braig enlisted the help of Ansem the Wise's other apprentices and exploited his research to experiment with separating hearts from bodies in order to create Nobodies of them all, leaving them hallow vessels ready to be filled with fragments of Xehanort's heart, as well as build up a destructive force of Heartless for their plans. However, as Xehanort himself also separated his heart and body, his Nobody, Xemnas, made plans to form an artificial Kingdom Hearts in order to gain the power to fragment his heart into the other Nobodies.

However, Xemnas and Braig knew through their research of Heartless and Nobodies that Nobodies could indeed cultivate hearts once more and develop emotions, as with the case of Roxas, Namine, and Axel. Knowing that this would entice the members of the Organization to disobey them, Xemnas and Braig deceived them all by telling them that Kingdom Hearts was the only way to recover their hearts.

However, most of the members were either too weak or turned traitorous before they could be turned into appropriate vessels, and had to be eliminated or were defeated by Sora and Riku. Xigbar, the Nobody of Braig, and Saix, the Nobody of Isa, were the only members that were strong enough and had gone through the initial stages of the cloning process. Xemnas, however, knew his younger self was assembling a fail safe group and continued on his plans to form Kingdom Hearts to gain absolute power, and embark on the next phase of his plans.

At the same time, Xehanort's Heartless destroyed thousands of worlds to form a Kingdom Hearts made entirely of darkness, and manipulated Maleficent into capturing the Princesses of Heart to use their hearts to locate the Door to Darkness in an attempt to extinguish their light and leave the worlds vulnerable to the darkness. However, this plan was promptly thwarted when Sora rescued the princesses and began destroying the members of Organization XIII, but Xehanort took precautions in case of such circumstances.

To this end, Xehanort's Heartless enlisted the aid of a younger version of himself from a separate timeline, and gave him the powers to survey time and space itself in order to enlist 6 different incarnations of himself, while Braig and Isa rejoined Master Xehanort, to create a new Organization XIII. Riku was originally intended to become the final vessel once Xehanort's Heartless seized complete control of his body, but this failed when the heartless was destroyed and Riku built up a tolerance to the darkness. Xehanort then moved his sights to the next best candidate&mdash; Sora, the same boy who contains the power of Ventus, Xehanort's first pupil, who is personified in Sora's nobody, Roxas, who was made from Ventus's heart.

Once this new Organization is formed, Master Xehanort intends to use them to eliminate the Princesses of Heart, thus throwing the worlds into turmoil and leaving them vulnerable to the darkness. Then, by having the thirteen members of darkness clash with the seven lights, the χ-Blade would finally be forged, the true Kingdom Hearts would resurface, finally complete, and the Keyblade War would begin anew. Through this war, Xehanort would finally gain all the answers he craved for most of his life, and become all knowing. Through the great darkness that would awaken, Xehanort would reorganize the worlds to one where light and darkness are balanced, in a universe under his rule.

Xehanort then attempts to make Sora his final vessel, but is stopped by Lea, who has volunteered to help Yen Sid protect the worlds from Xehanort. Xehanort then cruelly orders Lea's former best friend, Isa, to attack him and sends his Heartless and Nobody counterparts to restrain Mickey and Riku. As Riku, Lea, and Mickey fight off their opponents, Xehanort's Heartless and Xemnas are defeated with the timely arrival of Donald and Goofy. Unshaken by this minor setback, Xehanort informs all the heroes that the clash between light and dark is inevitable and bids them farewell as he looks forward to the start of the battles that will create the χ-Blade and escapes.

In the end, Yen Sid and Mickey prepare to form a group of seven Keyblade Wielders of light to stop Xehanort and his new army from murdering the Princesses of Heart and forging the χ-Blade to start a second Keyblade War, while fearing that such a war may be inevitable, as the seven lights and thirteen darkness' may be forced into conflict to prevent the deaths of the princesses.

Appearance
Master Xehanort appears as 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 immense power.

Master Xehanort's clothing is the same as that worn by his eventual Heartless, Ansem. It is composed of a white and black coat with a red inner lining, over a white shirt with two thin black belts, as well as white gloves and calf-high black boots. The major difference between the two outfits is that Ansem wears the shirt unbuttoned, exposing the Heartless emblem on his chest. However, there are a few minor changes as well; Ansem's coat has gold lining on its edges, where Xehanort's has black lining. Master Xehanort sometimes wears a Black Coat over this outfit.

In his youth, Master Xehanort had mildly tanned skin, golden eyes, and silver hair which both slightly spikes and falls past his shoulders in the back; it is styled similar to Xehanort's, albeit with four bangs framing his face - the back two thicker than the front two - and the two backwards spikes on the sides are absent, the topmost one slicked back. He wore the same style of white shirt, which only reaches to his thighs, a black vest with a high collar, long armbands which cover his forearms, and dark grey pants stuffed into his boots, similar to those worn by Organization XIII but absent of the silver lining on top, much like those worn by the guards of Radiant Garden.

In the English version of Kingdom Hearts: Birth by Sleep, Master Xehanort is voiced by Leonard Nimoy, who was chosen by Tetsuya Nomura specifically for his role as Spock in the Star Trek franchise. Nimoy also featured in the 1978 film, Invasion of the Body Snatchers, which is also similar, given Xehanort's tendency to steal bodies, having done so to Terra and Riku. Nimoy will reprise his role in Dream Drop Distance.

In the Japanese version of Kingdom Hearts: Birth by Sleep, Master Xehanort is voiced by Chikao Ōtsuka, who was chosen by Tetsuya Nomura specifically because he is the father of Akio Ōtsuka, the Japanese voice actor of Xehanort and "Ansem". Chikao Ōtsuka also previously voiced Captain Hook in the original Kingdom Hearts but was replaced by Naoya Uchida for Kingdom Hearts Birth by Sleep.

Personality
Much like Xehanort, "Ansem", and Xemnas, Master Xehanort is shown to be a cunning, callous, and pragmatic being with the sole goal of merging with Kingdom Hearts and become all knowing, the lives of innocent people and even his closest friends meaning absolutely nothing to him. To this end, he is willing to put whatever he pleases on the line or destroy anything in his way, demonstrated when he manipulated 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.

Despite his overweening malice, Xehanort has shown to have some slight sympathy, though the only known occurrence of this trait is when he takes pity on Ventus, following the rupture of his heart, and decides to leave him to die a peaceful death on Destiny Islands. All of Master Xehanort's other positive points are revealed to have sinister intentions behind them, demonstrated when he only took Ventus as an apprentice and cared for him solely with the intention of making the boy his vessel once he was strong enough, left him in Eraqus's care to simply make him stronger to be joined with Vanitas years later, and only accepted Master Eraqus's invitation to witness the Mark of Mastery Exam to sabotage it and put Terra on the path to darkness so as to make him his new vessel after deciding to instead use Ventus for the χ-blade.

Despite his sinister actions throughout the series, the root of Xehanort's malice appears to originate from his curiosity of how the universe was made and his lust to become all knowing. It is this trait that enticed Xehanort to leave the Destiny Islands in search of other worlds, ultimately starting his life as a Keyblade Wielder. This trait is shared throughout his various incarnations as Xehanort, Xehanort's Heartless, and Xemnas all justify their actions by believing that it is all for the sake of research.

His descent into darkness is owed partially by this lust as he wished to learn everything there is to about the worlds, including the Dark Realm. He does not believe in mindless violence or destruction without cause or motive, nor is sadistic in nature, shown by his merciful sympathy towards Ventus after rupturing his heart, but will willing engage in violence, cause destruction, and even commit cold-blooded murder if it benefits his quest for knowledge. Ultimately, knowledge and power are the only things Xehanort finds value in and only sees other living beings as tools to be manipulated if they are useful or destroyed if they are hindrances to his grand designs, but always with a greater purpose in mind.

Additionally, Xehanort's reports show the man in a different light than what is initially portrayed as an individual that does not cause destruction and tragedy for the sake of it, but to gleam answers from it. Unlike villains such as Maleficent, Xehanort does not seek to form Kingdom Hearts to purely obtain power, but to incite a Keyblade War and see firsthand just how the world was made from such a conflict. Through this observation, he would be able to become all knowing and create a universe that is more to his liking where light and darkness are more balanced.

While these motives of seeking knowledge and creating a more balanced existence were not initially evil in nature, they allowed Xehanort to feel no remorse for his actions and commit heinous atrocities throughout the worlds for years on end, turning Xehanort into a violent and amoral villain who is eventually consumed by his lust for knowledge, power, and darkness. Though Xehanort's goal of completing Kingdom Hearts is for various reasons, he is not above of being memorized by the absolute power that he would be granted through possessing the X-Blade and unlocking Kingdom Hearts; this lust and obsession would continue on with his Heartless and Nobody counterparts.

Regardless of his justifications and motives for his plans, Xehanort has shown an extreme disregard for all life. This disregard for life is seen in his ultimate goal of inciting another Keyblade War to simply quell his curiosity and remake the universe, which would cost the lives and billions of innocent people and the destruction of all worlds. He gleefully took the life of Master Eraqus, his former best friend, to simply make the darkness in Terra's heart stronger, showing that Xehanort's obsession with Kingdom Hearts overshadows even that of the care he once felt towards a man he saw as a brother.

His counterparts also share in his extreme disregard with his Heartless destroying thousands of worlds to form a Kingdom Hearts made of the darkness of their destroyed remnants and unleash it onto the worlds while his Nobody created millions upon millions of more heartless from the hearts of countless individuals and manipulated his own associates for his own ends, feeling no attachment to them watsoever and decieving their own emotions. This trait is also very indiactive of Xehanort's overall persona as he believes that only the emotions of anger and hatred within the heart gave one power as they feed the darkness within all hearts. Xehanort's complete disregard for human life, lack of any empathy or remorse, and disdain to any emotion within the heart aside from anger and hatred arguably makes him a psychopath, unable to feel any attachment to anything aside from Kingdom Hearts.

While possessing amazing skills, stamina, and powers, even at such an old age, Xehanort rarely brags about his skills and even accepts the fact that he is capable of being defeated. Knowing that not even he is unbeatable, Xehanort is always laying out numerous back up plans in case his original designs do not go as planned. This not only allows Xehanort multiple paths to take even if his schemes are spoiled, but keeps him one step ahead of all his adversaries, even the immensely wise and powerful Yen Sid. His modest demeanor and acceptance of possible defeat also contributes to his calm appearance as he knows that even in defeat, he still has other alternatives to turn to.

After taking over Terra's body, the villain retains all of his personality traits as the new incarnation of Xehanort (before the latter's fight against the Lingering Will and Aqua) and "Ansem", who's attire is the same as Master Xehanorts'. Xemnas, meanwhile, appears to be influenced several times by Terra's characteristics, such as his goal of locating Ventus and speaking to Aqua's armor as a fallen ally and friend rather than an enemy. Regardless, Master Xehanort's influence appears to be the primary and dominant conciseness controlling Terra's body and mind as all his forms are obsessed with Kingdom Hearts and completing the alternative plans that Master Xehanort had laid out prior to taking over Terra.

Lastly, Master Xehanort also has a few unusual tendencies and quirks as well, such as turning away from the people he speaks to, or over-dramatizing his hand gestures when delivering a speech, even flexing his fingers in an unusual manner, as if itching to grab something. These actions seem very indicative of his obsession and excitement over his plans and visions, nearly losing his calm composure when discussing over what can be achieved and when fulfilling the most essential steps of his elaborate plots and calculated betrayals.

Overall, Master Xehanort is the true catalyst, either direct or indirect, of all the events in the series so far, such as the creation of all his counterparts, Vanitas, the Unversed, the Emblem Heartless, and Nobodies, Organization XIII and the Disney Villains' hunt for Kingdom Hearts. He appears to be the most evil and dangerous of all of Xehanort's forms and where all their malice and evil truly stems from. What started as simple curiosity turned into pure malice and deception, turning the man into a massive threat and villain throughout all the worlds that has lived on through countless incarnations.

Abilities
His age often causing opponents to underestimate him, Master Xehanort is an extremely skilled Keyblade Master and magic user. Able to teleport if he is in danger, Master Xehanort strikes opponents with powerful, fast-paced combos. He also can bombard foes with Thunder, Blizzard, and Earth-based magic. His magic skills are some of the most advanced seen in the series so far, able to create massive rock formations and pillars, encase Ventus's body in ice, project a gust of wind powerful enough to send Ventus and Mickey flying from his hand, block Braig's Arrowgun shots without raising his arms, and telekinetically control the Keyblades covering the Keyblade Graveyard to attack Terra and Aqua. He also possesses physical strength sufficient enough to grab a fully-armored Ventus by the back of the head and lift him into the air with one hand.

Master Xehanort shows a great deal of skill in utilizing the heart and its capabilities, able to create a living being, Vanitas, out of the darkness of Ventus's heart when he unlocks it and even able to direct his heart into Terra's body to possess it after his defeat in the Keyblade Graveyard.

Once he becomes the young man known as Xehanort through the possession of Terra's body, Master Xehanort proves to be the stronger of the two hearts residing within him. Master Xehanort's overpowering Terra's is demonstrated several times during the battle between Terra-Xehanort and Aqua, Master Xehanort's influence beginning the fight in the first place and even releasing Terra's heart from within the body of his younger incarnation when Terra begins to regain control. Also, his combat abilities somewhat increase with the combination of Terra's power upped by Xehanort's agility.

His greatest asset, however, is his intelligence and skills at manipulation. For over eleven years, Xehanort's master plan has been going about, resulting in, among other things, the founding of the original Organization XIII and Riku's possession of the Seeker of Darkness.

Weapon
Master Xehanort is able to wield his Keyblade with great skill despite his age, and enough of his strength has remained over the years that he is able to use it in fast-paced physical combos. His battle pose is similar to that of both Vanitas and Riku, but he mainly allows the Keyblade to hang loosely at his side as he walks slowly towards opponents. Master Xehanort also uses his Keyblade to unlock countless hearts, including his own.

When Master Xehanort possesses Terra's body to become Terra-Xehanort, he abandons Terra's Keyblade and replaces it with his own. Terra-Xehanort wields the weapon with great skill, combining several of Terra and Master Xehanort's abilities to form his own deadly combos. As this Keyblade was gained by Terra-Xehanort through Master Xehanort's heart's more powerful influence, it is also used through Master Xehanort's influence to unlock Terra-Xehanort's heart.

Trivia

 * Ansem, Seeker of Darkness, made from the heart of Master Xehanort, is referenced twice in Kingdom Hearts: Birth by Sleep. First, Master Xehanort asks Terra to "Seek out the darkness that upsets the balance", similar to Ansem's title, and second, Terra tells Master Xehanort in Blank Points that "You're gonna get shown the door, old man", referencing Ansem's fate at the end of Kingdom Hearts.
 * In both versions of Kingdom Hearts: Birth by Sleep, the voice actor for the young Master Xehanort is uncredited.