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.
At some point in time, he was gifted the power to transcend time by his future Heartless in order to assemble a new Organization XIII in the future, consisting entirely of thirteen 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. 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.
By unknown circumstances, Young Xehanort would be given a black coat to wear while he traversed through time to carry out his mission. Prior to this, he wore a black sleeveless top with a long black gillet over the top, dark grey pants and black boots.
At some point in time, Xehanort was once again encountered by the robed figure he met back on the Destiny Islands, the same one who opened a portal for him to travel to Scala ad Caelum. The figure would give Xehanort the power to traverse and manipulate time itself, instructing him to travel forward into the ages to collect the various splintered versions of his heart and assemble them in the future to form the real Organization XIII. Unknown to Xehanort at the time, the figure he was talking to was none other than his future Heartless.
In order to travel through time, Xehanort was forced to leave his body behind in the past, appearing nothing more than a corporeal heart wearing a black coat, devoid of a true physical form. Now under the name of Young Xehanort, he soon departed from his time and traveled to the future, seeking out as many hearts connected to his as he could.
Birth by Sleep
As Terra, Ventus, and Aqua each return separately to the Land of Departure's remains, they turn around when they feel a presence and find a hooded Young Xehanort, who challenges them to a battle. After the fierce battle, they seem to have lost sight of the mysterious figure, and prepare to walk away when Young Xehanort appears before them again, but he only walks away in the direction of the castle and disappears, fading out of sight.
Between Birth by Sleep and Re:coded
During his travels through time, Young Xehanort came to acquire the hearts of Vanitas, Riku Replica, Ansem and Xemnas prior to their demises to recruit them as members of the real Organization XIII. He would also at some point come into contact with the complete selves of Luxord, Larxene and Marluxia following their restorations to induct them back into the real Organization as their respective Nobody selves.
Not long after the defeat of Xemnas in the present day, 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 discusses with Young Xehanort on Master Xehanort's intentions before asking the youth which of the comatose apprentices to take with them. Young Xehanort smiles, and picks Saïx.
Dream Drop Distance
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.
Young Xehanort first reveals himself to the duo in Traverse Town, where he strikes a deal with the participants of the Reapers' Game to bring him Sora and Riku, though his dealings fall through, leaving him to summon the Hockomonkey for them to fight. From then on, Young Xehanort would meet with the two individually as they continued their test. In La Cité des Cloches, he confronts Sora in the cathedral alongside a faint apparition of Vanitas, critiquing him for his ignorance on his heart's status as a prison. He later appears on the roof of the cathedral alongside Ansem, taunting Riku for his lingering fear of darkness. In Prankster's Paradise, he appears alongside Xemnas as he talks to Sora about the possibility of Nobodies having hearts, and again at The Grid, where he cryptically tells Sora that he has wandered off of his set path. In Symphony of Sorcery, he meets with Sora atop a small ridge, commenting on the idyllic nature of the world while telling him that they would meet again should he sleep on. He then meets with Riku for the first time since La Cité des Cloches, stating that his resistance to darkness meant that he was of no use to him before summoning Chernabog to fight the boy.
Upon Sora's arrival to The World That Never Was, Young Xehanort guides him through various past memories, explaining the deeper significance within them, as well as the mechanics of how time travel works. After Sora learns from Xemnas that Nobodies could in fact generate new hearts and that the true purpose of Organization XIII was to serve as vessels for Xehanort's heart, he engages the Nobody in battle, which wears Sora down to nothingness, weakening his heart. Young Xehanort appears beside him, revealing his intentions to turn him into the final vessel of his new Organization before putting him in a deep sleep. Sora is taken to the Organization's former headquarters, while Riku and King Mickey attempt to save him. Young Xehanort impedes their attempts and engages Riku in a brutal fight with his 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.
Kingdom Hearts III
With their time up as corporeal hearts, Young Xehanort and the other time-traveling members of the Organization are forced to return to their original times, though they would 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, thus allowing them to remain anchored to the present.
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 before vanishing. Young Xehanort would later confront Sora and Jiminy Cricket in San Fransokyo, chastising the former on his reckless misuse of the power of waking to save the hearts of the fallen guardians of light. Before departing through a corridor of darkness, he warns Sora of a costly price he would have to pay for his actions.
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 darknesses 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 reminds him of the high price required 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, making him the twelfth member of the real Organization to fall.
Following his elimination, Young Xehanort's heart was returned to its proper place in time with no memory of the experiences he witnessed in the future. Despite this however, they remained engraved in his heart, and would ultimately guide him to his destiny as the elderly Keyblade Master who desires to forge the χ-blade and open Kingdom Hearts.
One year after Master Xehanort’s defeat and Sora's disappearance, a data recreation of Young Xehanort, along with the rest of the real Organization XIII, is fought by a digital copy of Sora with the hopes of uncovering the real Sora's location from the encrypted data they possessed. After defeating all thirteen data recreations however, the results proved inconclusive.
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, 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' 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 again 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 starting after the real Organization's first assemblage at The World That Never Was.