I am Xehanort from the most distant past. My future self gave me a task - to visit the splintered versions of myself in many worlds, and ensure they gathered here today.
During a training journey to prepare for his upcoming Mark of Mastery exam, he was encountered by his future Heartless on the Destiny Islands, who gifted him the power to transcend time in order to assemble a new Organization in the future, consisting entirely of vessels infused with a fragment of his heart.
Young Xehanort displays a near-identical personality to his future self as Master Xehanort, though he is shown to be slightly cocky and arrogant as a result of his youth.
Young Xehanort has mildly tanned skin with pointed ears, golden eyes, and silver hair; originally however, he possessed silver eyes and had rounded ears as a boy, and would later gain pointed ears as he grew up while obtaining his golden eyes after mastering control over darkness. His hair slightly spikes and falls past his shoulders in the back, and he has four bangs framing his face, similar to Terra-Xehanort’s hair when he became Ansem the Wise's apprentice.
As a teenage Keyblade wielder, Young Xehanort wore the same style of white shirt similar to his future self and Heartless, a black vest with a high collar, long armbands which cover his forearms, and dark grey pants stuffed into his boots. When he acquires the power to time travel, Young Xehanort acquires a replica body from the future in order to remain during his travels. With his heart contained within a replica, the replica becomes modeled after him physically, although he wears a black coat instead of his normal outfit, though he later acquires a black coat of his own after returning to his time.
In Kingdom Hearts Birth by Sleep, Young Xehanort's body is completely covered by a hooded black coat with a fairly tall and masculine build. He never speaks at any point of the game.
Before Kingdom Hearts Birth by Sleep
This was where it started. At this point, I still had no idea that I was talking to myself.
Young Xehanort to Sora
In his youth, a boy named Xehanort left his homeworld of the Destiny Islands. He found his way to Scala ad Caelum, where he would begin training as a Keyblade wielder alongside his brother-in-training Eraqus. He would often play games of chess with him in-between their lessons, discussing the Lost Masters that started the Keyblade War and theorizing that the future was all but written by the Gazing Eye, though Eraqus remains confident that a predetermined future could be changed.
Years later, a teenage Xehanort began a training journey in preparation for his upcoming Mark of Mastery exam. While visiting many worlds, he returned to his homeworld, commenting that it was too small. Not long after, he was visited by a robed figure, who gifted him the power to travel through time, and instructed him to gather various hearts throughout time that had a strong connection to him and assemble them in the future; unknown to Xehanort at the time, the figure he was talking to was his own future Heartless.
After finishing his role, Young Xehanort was returned to his proper place in time with no memory of the future; however, these lost memories would remain etched in his heart, giving him a sense of direction for what he desires in the future. After resuming his journey, he meets a hooded figure in a black coat, who gifted Young Xehanort a black coat of his own. The two meet at the Keyblade Graveyard, discussing Young Xehanort's thoughts for what he wishes for the world and those who are tainted by the darkness of their own self-ambitions. At the end of their discussion, Young Xehanort questions the hooded man on his identity, to which he reveals himself to be one of the Lost Masters. The figure soon walks away, muttering the old Keyblade mantra "may your heart be your guiding key" while leaving Young Xehanort baffled.
As Terra, Ventus, and Aqua return separately to the Land of Departure's remains, they turn around when they feel a presence and find a hooded figure who challenges them to a battle. After the battle, they seem to have lost sight of the mysterious figure, and prepare to walk away when they spot him again, but he only walks away in the direction of the castle and disappears, fading out of sight.
Young Xehanort is shown as the first incarnation before both Ansem and Xemnas, and appears in his elderly form after them.
Not long after the defeat of Xemnas, the human counterparts of the first eight members of Organization XIII reappear in Ansem's Lab in Radiant Garden. The first to awaken is Braig, being done so by the time-traveling Young Xehanort. Remarking that things were back on track, Braig soon chats with Young Xehanort on the latter's future self's intentions before asking the youth which of the comatose apprentices to take with them. Young Xehanort smiles, and picks Saïx.
Young Xehanort appears numerous times to Sora and Riku during their Mark of Mastery exam as they traverse the Realm of Sleep and awaken several worlds previously destroyed by Ansem, Seeker of Darkness. During these appearances, Young Xehanort would taunt the two as he recruited other versions of himself throughout time and space to complete the real Organization XIII under Master Xehanort's orders. The original Organization XIII was meant to recruit thirteen strong beings to be used to make clones of Master Xehanort through the process of transferring portions of his heart into their bodies, but the first generation of Nobodies consisted of many failures. A majority of the original members were either traitorous to the Organization, were too weak for their purpose, or were simply distrustful. Young Xehanort then embarked on his mission to find suitable replacements; various versions of himself, throughout time. To this end, Xehanort recruited Ansem and Xemnas to the new Organization.
As the story progresses, it is revealed that Ansem once traveled back in time and set this younger version of his former incarnation on his journey as a fail safe should Xemnas' Organization XIII prove to be useless in his plans. After Sora fights Xemnas which damages the former's heart, Young Xehanort puts him into a deep sleep, planning to use him as the final vessel in his new Organization XIII. Sora is taken to the Organization's former headquarters in The World that Never Was, while Riku and King Mickey attempt to save him. Young Xehanort impedes their attempts and engages Riku in a brutal fight with his newly-acquired Keyblade, where Riku comes through victorious, but Master Xehanort returns immediately after the fight to assume control over his new army. Young Xehanort takes his place among the ranks under his older self's rule and escapes with all his counterparts, once Riku, Mickey, Lea, Donald, and Goofy prevented Master Xehanort from transferring a portion of his heart into Sora to make him his final vessel.
Without the temporal flexibility of the Sleeping Worlds, Young Xehanort and the other time-traveling members of the Organization are forced to return to their original times, though they soon regather in the future once more, this time with refined replicas from the early batches of the Replica Program waiting for them to use as vessels for their hearts.
Young Xehanort reveals himself to Sora and company at Toy Box, revealing that he had split the world in two and scattered its inhabitants among the two halves. He goes on to explain that he was using the world's unique property of living toys with hearts to conduct an experiment that would allow the Organization to obtain their final vessel, though he remains cryptic with most of his plan's details. After appearing before the group again at the video game store, he unveils that he was using Woody and Buzz Lightyear as the prime candidates for his experiment, stretching the limits of their friendship and trust with Buzz's insecurities of Sora in order to create a pawn of darkness out of Buzz. However, Sora, Woody and company are able to save Buzz from Young Xehanort, though he remains confident with the results of his experiment before leaving the world, but not before telling Sora to find the hearts joined to his and summoning the King of Toys for them to deal with.
Young Xehanort later appears in the Keyblade Graveyard, appearing in front of Master Xehanort, Ansem, and Xemnas with Vanitas; Vanitas comments that once the Guardians had been broken by battle upon battle, the χ-blade can be complete, with Young Xehanort adding that it is what they must do, for it has been "etched". The five darknesses soon unleash a massive swarm of Heartless, Nobodies, and Unversed to attack the Guardians.
During Sora's attempt to use the power of waking to rescue his fellow Guardians from the Lich after their defeat by Terra-Xehanort and a Heartless swarm, Young Xehanort appears before him and Jiminy Cricket in San Fransokyo. He comments that his gallivanting through the Sleeping Worlds had taught him nothing, and that he nearly buried himself in the depths of sleep, comparing it with Sora's current situation. He explains that the Lich he had been fighting was unlike any Heartless he had previous encountered, for its existence was to usher hearts down into the abyss of darkness, telling Sora that he would condemn his heart to that same abyss should he continue chasing it. When Sora claims his heart was strong, Young Xehanort asks him what he thinks the power of waking is, revealing that it was for traversing hearts to reach other worlds, not the other way around. He adds that misusing such a power would come at a great cost, to which Sora sarcastically questions if he was now worried about him, although Young Xehanort denies, remarking that there was no saving him. Before leaving through a corridor of darkness, Young Xehanort tells Sora that the price had been paid, and it lies as the bottom of the abyss before disappearing.
Young Xehanort later walks with the rest of the Organization as they confront the Guardians at the crossroads of the Keyblade Graveyard before Master Xehanort creates the Skein of Severance to serve as the battlegrounds of the Keyblade War. After nine of the thirteen Organization members had fallen, Young Xehanort joins Ansem and Xemnas atop the Tower of Endings to fight against Sora, Riku and King Mickey in one of the last battles of the Keyblade War. After being defeated, Young Xehanort falls to the ground, laughing. Sora asks what was funny, to which Young Xehanort says that there was a high price to pay for all of this. When asked what that would be, Young Xehanort ignores the question and stands back up, saying that he will go back to his time to live out his life, but tells Sora that his journey has reached its end. As he told a satirical goodbye to Sora, he tells him that his time in the world was up, although he is cut off mid-sentence as his replica body fades away while his heart returns back to its proper place in time, making him the twelfth member of the real Organization to fall.
Young Xehanort wields many incredibly formidable abilities that makes him an extremely powerful foe to behold. He was granted the power of space-time manipulation by Ansem, which he uses to great effect; for example, he recovered from the effect of Mickey's most powerful Stop spell within mere moments, far faster than any of his comrades. He can manipulate time so precisely that he is capable of controlling time to achieve a myriad of effects while in battle, performing such feats as slowing his opponent or reversing the flow of time to regenerate health. During his battle with Riku, Young Xehanort would merge with the clock in the arena and if enough time has been given, could restore a decent amount of health by rewinding time. Like his older self, he is an extremely powerful magic user, capable of casting many of the most powerful spells available to all the protagonists of Kingdom Hearts Birth by Sleep, with the addition of being able to use Doom, and he can cast powerful fire, wind and ice spells that project fiery vortexes, summon tornadoes and fire several large ice blocks. His telekinetic prowess is capable of easily throwing around Riku and Mickey.
In every boss encounter, Young Xehanort is immune to all status effects and displays outstanding swordsmanship skills as well as great speed and agility, wielding first his dual-blades to perform many deadly attacks, also displaying proficiency with the whip and spear form the weapons can undertake by fusing them together, and later his Keyblade to quickly unleash a flurry of combos capable of trapping and quickly dealing heavy damage to Riku, with him also making effective use of his ability to transform it into a shield and whip. In Birth by Sleep, Young Xehanort is also capable of turning himself invisible and firing lasers. In Dream Drop Distance, he can enter the World of Sleep, summon Dream Eaters, open Keyholes and the Corridors of Darkness.
In his initial appearance, Young Xehanort wields two weapons that bear a striking resemblance to Xemnas's Ethereal Blades, but appear to have hilts, which many of Xemnas's blades do not, but they also resemble some clock hands or clock arrows. The blades are made of light blue energy and the black handles are somewhat reminiscent of the Terminus and Ruination Ethereal Blades. The blades can be combined into a dual-blade, and extend to be lashed out like a whip. Young Xehanort wields these weapons with a reverse grip, similar to the unorthodox way Ventus wields his Keyblade. He would later wield these blades during the second phase of his battle with Riku in Where Nothing Gathers.
Young Xehanort is later revealed to have to power to wield a Keyblade that incorporates elements of the No Name and the Gazing Eye Keyblades, using this as his main weapon of choice instead of his ethereal blades starting after the real Organization's first assemblage at The World That Never Was.