Zexion makes his debut as a boss in Kingdom Hearts II Final Mix and Kingdom Hearts Re:Chain of Memories, and is also fought inKingdom Hearts Union χ. Originally intending to recruit Riku as an aid against the rebellious Marluxia, Zexion and the boy later clashed after Marluxia's destruction, Riku naught but an annoyance to Zexion and, to a lesser extent, the Organization, with the traitorous Organization members having been defeated. Conquered by Riku during their climatic battle and later eliminated by the Riku Replica, Zexion later appeared before Sora as both an Absent Silhouette and a Data Rematch.
Kingdom Hearts Re:Chain of Memories
The battle against Zexion can be quite an annoyance and difficult to overcome. Fortunately, Riku will remain in Dark Mode for the entire battle, granting an increase of strength and speed, as well as the ability to use Sleights. Despite this, it is recommended that Riku have a relatively high AP level, ensuring he deals as much damage as possible through any means of offense.
Zexion's main strategy is to continuously steal Riku's cards in order to prepare for his more threatening techniques; this is done mainly by throwing the Book of Retribution in Riku's direction. If this attack hits, Riku will lose three cards. These cannot be reloaded while in Zexion's possession, but this tactic can be successfully dodged by Dark Mode's "Quick Run". However, Zexion has one last method of stealing Riku's cards, his only available Sleight in early stages of the battle, Cyclone Snatch. During the execution of this Sleight, Zexion will create a black vortex in the center of the battlefield. This vortex will draw Riku in so long as it remains, dealing slight damage when he touches it and stealing two cards per hit. Cyclone Snatch can be avoided, however, by continuously using "Quick Run" towards the edge of the battlefield until the attack ends.
When Zexion has collected enough cards, three copies of the Book of Retribution will appear in the corners of the battlefield, glowing with a mysterious aura. Zexion's deck will convert from his all-magic one to a deck comprised of Riku's stolen Soul Eater Cards, three copies of Zexion appear alongside him, each with a false Soul Eater in hand. When Zexion uses a Soul Eater card, his clones will rush at Riku, slashing him, the combo ending with a downward slam from Zexion himself. Zexion also will have access to two very powerful Sleights, Dark Punisher and Catastrophe. During Dark Punisher's execution, Zexion will grab Riku from behind and slowly damages him. Only a Card Break will free Riku from the boss's grasp. Catastrophe is far more deadly, however; Zexion summons a sphere of light energy in the center of the battlefield and shoots a laser beam at it while any remaining clones do the same. Zexion and his clones rotate around the area. Again, only Card Breaks will allow Riku to escape.
This execution of powerful melee attacks and Sleights will continue until the four Lexicons are destroyed, which can be done through careful utilization of aerial attacks or even an Inverse Burst Sleight by using a King Mickey Friend Card. Not only will destroying a Book of Retribution cause a Zexion clone to vanish (decreasing the number of hits landed in his standard combo), but it will also relinquish EXP. Successfully destroying all four Book of Retribution copies will cause all the remaining Soul Eater cards that Zexion stole to reappear on the battlefield; picking them up returns them to Riku's deck for normal use. Take extreme caution once the Book of Retribution copies are first destroyed, as Zexion may place a decoy Soul Eater card (recognized by its unique coloration) amongst the fallen cards he had previously stolen. Should Riku use this card unwittingly, he will take damage and be stunned for a time, opening him up for more damage and allowing Zexion to easily steal more cards. His most powerful techniques no longer available, Zexion will then revert to his card-stealing strategy.
Utilize Card Duels whenever possible. Dark Barrage can be especially powerful when one has a high AP level, and the fact that it can hit multiple targets will allow Riku to destroy Zexion's Book of Retribution copies, causing EXP to drop as a result. Zexion's attacks should be Card Broken whenever possible, as most will be unavoidable if this does not occur. Sleights should also be used to the Riku's advantage; even though Riku's poorly composed deck will only allow usage of Dark Break and Dark Firaga, a high AP level greatly increases the damage done by these attacks. Despite the great advantage Sleights will provide HP-wise, they should not be abused, as continued use of Sleights to deal heavy damage or Card Break an attack will quickly reduce Riku's number of usable cards from the beginning amount of 23 to one or two; this negative side-effect is only worsened by Zexion's card-stealing abilities.
Being left with only low-numbered cards will greatly hinder Riku once Zexion summons his clones, as he will use higher card values than usual during this time, making destroying the Book of Retribution copies a difficult task. The lack of high-valued cards in Riku's deck makes it almost impossible to stop Zexion's Sleights. Any King Mickey cards should be saved, as they will be useful for replenishing Riku's HP if it ever drops to the Alarm Zone. If Zexion ever utilizes his Enemy Card, which grants him the Confu-Strike ability, be cautious, as any attack utilized by him will have a chance of inflicting the Confused status on Riku. While confused, Riku's controls will be reversed. This can be an extreme hindrance when it comes to dodging. If Riku ever needs extra support mid-battle, an Enemy Card such as Jafar, Maleficent, or Oogie Boogie can be used.
Kingdom Hearts II Final Mix
Zexion appears as an Absent Silhouette. Due to the absence of cards in the game, Zexion's attack style has been completely changed.
At the start of the battle, Zexion will attempt to trap Sora and friends within the Book of Retribution. In order for any member of the trio to be trapped, they must stand within the path of the glowing symbol Zexion summons before him. If Donald or Goofy is trapped, they will alert Sora by shouting his name, needing to be released from the book through physical combos. Once it is destroyed, the character held captive will be freed.
If Sora is captured, he will be sent to a parallel dimension contained within the Book of Retribution. Here, Sora will be bombarded by copies of the Lexicon and must find Zexion, who has concealed himself within the true one. Once the Book of Retribution hiding Zexion has been located, its HP bar must be depleted and the "Dispel" Reaction Command must be used to return Sora to the real world. In the mean time, Sora may be able to utilize a unique, non-offensive Reaction Command. This will allow him to obtain much-needed Drive Orbs and HP Orbs mid-battle via the command menu. Abilities such as Donald's Comet Limit will prevent Sora from taking damage from the Lexicons as they rain down on him, also dealing damage to Zexion's book. Limit Form is a recommended Drive Form for use when within the pocket dimension, as its HP-restoring attacks will also deal great damage and not cause Donald or Goofy to disappear. Once "Dispel" is used and Sora is returned to the real world alongside Donald and Goofy, bombard Zexion with both ground and aerial combos.
As Zexion's HP begins to dwindle, he will capture Sora and send him to a different area of the pocket dimension. Three circles of light, two red and one blue, will then appear on the ground. The colors of the circles will then proceed to shuffle around, changing thirteen times in total. When the final shuffle occurs, Sora will have only a moment to enter the blue circle, requiring use of Quick Run for consistent success. Success will surround Sora, Donald, and Goofy in a protective barrier, allowing them to attack the concealed Zexion. Failure to do so will cause Sora and the party to be bombarded by meteors. A long-lasting Limit such as Duck Flare or Comet can be used to prevent damage, but Sora can also rely on the Once More or Second Chance abilities if he has them equipped and then utilize Cure or a Potion when the attack ends. Sora, Donald, and Goofy will then be transported back to the first area of the pocket dimension, Zexion again needs to be located and attacked so that the "Dispel" Reaction Command can be used. Zexion can then be bombarded by physical attacks or spells such as Fire and Thunder until defeat, Zexion relinquishes the Book of Shadows Recipe as a reward for being defeated.
The Data Rematch against Zexion will flow similarly to the battle against his Absent Silhouette. The only differences will be the amount of HP he has and the pattern in which he uses his attacks. Simply recall the strategy used in the Absent Silhouette battle and use the "Dispel" Reaction Command when trapped within the Book of Retribution. Sora also should be of a relatively high level, using spells such as Curaga and Reflega, as well as Drive Forms and a powerful Keyblade such as the Ultima Weapon. The reward for defeating the Data Rematch is a Lost Illusion.
Sleights and attacks