Zexion appeared in Kingdom Hearts: Chain of Memories as a participant in the struggle within the Organization between the newer and veteran members. He is also central to the plot to use Riku as a puppet in Castle Oblivion. Zexion also appears in Kingdom Hearts 358/2 Days, as one of the playable characters in Mission Mode.
He's No. 6 in the Organization. Zexion generally avoids dirtying his own hands when there are deeds to be done. However, with the destruction of Vexen and Lexaeus, he was forced into action. Disguised as Sora, Zexion confronted Riku. But Riku no longer feared the dark, and victory was beyond Zexion's reach. After Sora had been lured into Castle Oblivion, Zexion discovers two other scents deep in the dungeons of the castle. One of them belongs to a Maleficent formed from someone's memory, having been given life by Castle Oblivion's unique properties. Originally, he mistakes the other scent to be that of "The Superior". Eventually, however, Zexion and his cohorts determine that the scent belongs to Riku, who had appeared in the castle by force of will after Sora's arrival. Vexen hypothesizes that the darkness in Riku's heart, "Ansem Seeker of Darkness", caused Zexion to mistake him for "the Superior", calling the effect "fascinating." Specifically, Riku's heart is plagued by the presence of Ansem.
Zexion, as well as Lexaeus and Vexen, come to see that Marluxia, keeper of Castle Oblivion, intends to take control of Organization XIII, with the help of Larxene, by using Sora as their puppet. Though they see that they can use Riku to counter Sora, they decide to oppose Marluxia's plot by having Vexen investigate Marluxia under the guise of offering to help using the Riku Replica he creates with combat data from the real Riku. However, Vexen is eventually killed on Marluxia's orders by Axel, whom Zexion and Lexaeus had been unsure about trusting. Axel later tells them he had performed the deed only to gain Marluxia's trust, and continues to cooperate with Zexion in tracking Sora and Riku.
Seeing that Vexen's efforts to derail Marluxia's plan had failed, Zexion sends Lexaeus to sway Riku into joining them, but Riku refuses to allow darkness to control him and defeats Lexaeus in combat. With the last of his strength, Lexaeus manages to knock Riku unconscious, rendering him helpless. However, before he can finish the job, Ansem takes control of Riku's body and finishes Lexaeus with the power of darkness. Riku is then enveloped in his own personal darkness, where "Ansem" tries to corrupt him—however, he is saved by King Mickey and continues ascending Castle Oblivion.
After Lexaeus dies in his failed attempt to subvert Riku's resistance to darkness, Zexion discusses the Organization's fate with Axel and learns that Larxene has been killed as well, bringing the number of Organization members eliminated to three. Axel tells him that he himself was defeated by Sora as well, and that Marluxia is almost certainly the next to go. Zexion decides that with the possibility of Marluxia dying soon, Riku is no longer needed, and heads off to intercept him.
Zexion appears before Riku while he is between floors of the castle, shortly after the death of Marluxia. As the force of Marluxia's death shakes the castle, Riku halts with surprise and comments how a very strong scent in the air has died. Zexion materializes in front of him and tells him that Sora has just defeated Marluxia. Riku is surprised to learn that Sora is also in the castle, but Zexion tells him he would never be able to face him after having such darkness in his heart.
He gives Riku a World Card to Destiny Islands. While he explores it, Zexion reappears, and continues to play on his guilt, telling him Sora will always oppose him as a host of the dark. Zexion vanishes and Riku winds up facing a Darkside Heartless. After he defeats it, Sora then appears himself, brandishing his Keyblade and accusing Riku of being corrupt. He envelops Riku in light, rendering him unable to do anything. Instead of drowning Riku into helplessness, however, the predicament causes Naminé to come to his aid. In the guise of Kairi she tells him that he should stop rejecting the darkness within his heart, and instead draw on that power to free himself of the oppressing light and strike out at Sora.
He wounds Sora, whose disguise falters to reveal Zexion, who had been using his powers of illusion to deceive Riku. Zexion is astounded by Riku's ability to control the darkness, and is also enraged at his perseverance. He decides to engage Riku in combat himself, albeit wounded, but still puts up a rather difficult fight. However, Riku eventually overcomes and defeats Zexion.
After escaping from Riku, Zexion appears in the meeting room he shared with Lexaeus and Vexen, flabbergasted as to how Riku can wear darkness the way he does as no one has ever done so before. Waiting for him are Axel and a companion. In a panic, Zexion thinks Axel's companion is Riku himself, but then realizes it's only Riku Replica. Axel and the replica then approach Zexion, and Axel directs the replica's attention to his lack of wholeness. He tells him that if he can find strength that the real Riku doesn't have, he can become a whole person of his own, rather than a mere puppet or whole copy of Riku.
Axel then suggests that he should start by eliminating Zexion and taking his powers for himself. Zexion is horrified by Axel's suggestion and tells him he can't do that, but before he can do anything, the replica absorbs Zexion's life force, taking his power; judging by Axel's line of Zexion finding out "way too much", Axel having purposefully set this up in order to move Saïx up within the ranks of the Organization.
Initially, Zexion was never seen in combat, and his weapon and attribute were a mystery. In an effort to keep Zexion's weapon unknown, his gravestone in the The World That Never Was laid destroyed, as all the gravestones depicted the member's weapon of choice. Kingdom Hearts Re: Chain of Memories and Kingdom Hearts II Final Mix revealed his weapon as the Lexicon. Zexion can use his Lexicon to mimic the attacks of his enemies in Kingdom Hearts 358/2 Days and in Kingdom Hearts Re:Chain of Memories.
He is also seen to be able to change how he appears to others. In Kingdom Hearts Re: Chain of Memories, he takes the form of Sora to taunt Riku in Destiny Islands. He envelopes Riku in light, thinking that he would drown into helplessness. After freeing himself, Riku strikes Zexion, causing his disguise to fade and revealing himself.
This ability follows a trend where the Organization members bear abilities and skills mirroring those of Final Fantasy jobs (ex. Xaldin = Dragoon, Luxord = Gambler, etc.). In Zexion's case, his abilities mirror those of a Blue Mage, who can learn and mimic enemy attacks, or possibly a Mime who can perfectly imitate the most recently used ability.
In one, Zexion's copies vanish while Zexion grabs Riku and drains his HP. Zexion's other new sleight is a sleight in which he and his copies vanish and then reappear near the perimeter of the island and each fire an energy beam. The beams meet and slowly form a ball of energy as Zexion and his clones rotate around the island before the energy ball explodes over the entire island. In Kingdom Hearts Re:Chain of Memories, he has a unique fighting style; he steals and hoards his foe's cards until he has enough to use it in his own deck. He has copies of his lexicon float around and attack the opponent. His standard attack steals Riku's attack cards, and his standard sleight creates a tornado of dark energy that drags Riku in, and then damages him while stealing his cards. When Zexion hoards enough cards, he copies the Soul Eater and copies himself, gaining the uses of two new sleights.
His standard attack now becomes a combo with each of the copies slashing once in turn. Meanwhile, the lexicons are spreads out through the island encased in blue flames. Each of those lexicons support and act as the health of a clone. Destroying a lexicon causes a clone to disappear, and the destruction of the last copy frees all the stolen cards, and Zexion reverts to attacking with his lexicons until he hoards enough cards again. However, even if Riku manages to steal his cards back, Zexion occasionally prepares a countermeasure of sorts by planting a dummy Soul Eater card amongst the scattered pile for Riku to collect. The card is distinguished by the "wing" of the blade's design being orange instead of red, as well as the Soul Eater facing the opposite direction. If the card is collected then used, it damages and stuns Riku momentarily, giving Zexion an opening to steal cards again.
In Kingdom Hearts II Final Mix, Zexion returns as an optional boss. Zexion's fighting style is totally different; however, in the islands, his Absent Silhouette's only attack is to seemingly ensnare his prey in his lexicon, through use of illusion, causing them to hallucinate and physically feel any damage they believe they are taking. Once they have fallen victim to the illusion, they begin to see an area where lexicons float around, being conducted by Zexion, who makes himself appear as a lexicon himself to hide.
Only the reaction command, Dispel, used on Zexion after depleting his fake HP frees them from the hallucination. Meanwhile, they are either bombarded by lexicon copies and explosions, ensnared in life-draining lexicons, or have their commands mixed up. However, if the right commands are selected, HP, MP, Munny balls, or experience points can appear, while another command temporarily removes all the decoy lexicons.
His greatest attack involves creating another illusion, which causes the victim to see a pitch black room, save for three spotlights, one of which will be blue. The blue light will rotate between the three lights thirteen times until it comes to a complete stop, after which the entire area will be bombarded by meteors, with Zexion's laughing heard. However, the spotlight where the blue light stops on will be protected by a barrier. Zexion is also forced into the barricaded area, leaving him vulnerable to attack.
In both instances, he is shown to be a particularly powerful opponent, noted by many to be more difficult than Ansem, Seeker of Darkness inKingdom Hearts Re:Chain of Memories Reverse/Rebirth.
In Kingdom Hearts 358/2 Days, Zexion has a Limit Break called Meteor Mirage. During Meteor Mirage, Zexion and his open lexicon are brought into the air. While in the air, Zexion summons many balls of dark indigo energy to bomb the field, dealing a large amount of damage to enemies hit by the barrage. During the bombardment, Zexion cannot move around to hit enemies that are further away with the meteors but, if you press B, you can cancel the limit to run to a better position and then press A to resume the attack.
During Zexion's Final Limit, Zexion exerts more power into his lexicon for the attack. The meteors that he summons are larger and more plentiful, and crash down faster.
Also in 358/2 Days, during Mission 03, Zexion displays use of the Fire and Blizzara Panels.
WeaponZexion uses a book called a Lexicon, the Greek term for a dictionary. Its main form is named the Book of Retribution. It is unclear exactly what the pages contain, but from what can be seen, it tells some sort of story and lacks a basic dictionary layout. The cover displays three interconnected Nobody symbols. The back bears the outline of another Nobody logo. The spine of the book displays a Roman number six (VI), along with the title "Hallucination—Another Side", superimposed over yet another Nobody symbol.
Zexion has the power to seemingly trap people within the pages themselves, sending them to a different dimension where he can hide from them and attack. Although it is quite possible this is just a hallucination that his foes experience after looking into the green light emitted from the lexicon. He can also hide himself in the pages through use of illusion to make it appear he is actually inside them.
An accessory based off the lexicon called the "Shade Archive" can be synthesized in Kingdom Hearts II Final Mix.
Role in the series
Zexion was actually considered to be resurrected back to life and into the Villain League. He was intended by Mang to be used against Twilight Sparkle since both have fondness for books for another attempt to snag Kairi during Twilight's birthday sometime after the events of the Pirate Season 2 starter episodes had passed. Zexion's resurrection was entrusted to Dr. Blowhole in light of Junjie's "failed" resurrection of Vexen. The resurrection went without a hitch this time, and Zexion was brought before Xemnas and Xehanort, with Blowhole instructed to leave afterwards. However, Zexion smelled his darkness was far worse than what was expected. Zexion eventually forced Xehanort to confess he plans to enact The Great Cycle. Zexion protested it is against even the standards of darkness, which only invited Xehanort to order his recorruption, once again entrusted to Blowhole. The Corruption Temple was in the midst of a near-successful corruption, but Axel and the reformed Nobodies (Minus Vexen) appeared and saved Zexion, wiping Blowhole's memory of the event, and damaged the Corruption temple enough to make it look like another accident. Mang was upset he lost Zexion from another convenient accident, and cancelled the plan, which resulted in following Junjie's backup plan of being inside Twilight's birthday cake, and the rest, was history. Axel didn't have much trouble winning Zexion over. Zexion knew well enough the Great Cycle isn't something that should be toyed with, and become their other strategist like Vexen.