True, we don't have hearts, but we remember what it was like. That's what makes us special.
Saïx, the Luna Diviner (月に舞う魔人 Tsuki ni Mau Majin?, lit. Demon Dancing in the Moon), is the Nobody of Isa, Rank VII within Organization XIII, and Rank VIII within the real Organization XIII. He is a major antagonist in Kingdom Hearts II and Kingdom Hearts 358/2 Days, acting as the second-in-command to Xemnas, and later returns as a member of the real Organization XIII in Kingdom Hearts 3D: Dream Drop Distance and Kingdom Hearts III. He derives power from the Moon, and uses this power to enter a berserk rage where he mercilessly attacks opponents with his massive claymore. He commands the Berserker Nobodies.
Saïx is the second-to-last member of Organization XIII to fall. Along with all other Organization members in Kingdom Hearts 358/2 Days, Saïx is a playable character in Mission Mode.
Next to Xemnas, Saïx appears to be one of the most "Nobody-like" of the Organization. Despite claiming to remember what possessing a heart was like, he behaves mostly as a cold, emotionless, and efficient operative until his final battle. In almost all of his appearances, Saïx acts very calmly, never losing composure in even the direst of situations. He is very aware of how emotions are unreal to them, unlike other members who imitate their emotions. He instead uses his memories of a heart to cruelly manipulate the hearts and behavior of others. He coldly toyed with Sora's emotions by having him beg to see Kairi, only to refuse his request. Saïx also sent the "useless" members to their deaths at Castle Oblivion under the guise of Xemnas's orders for the sake of his and Axel's plans. This was a smart tactic to simultaneously move up his rank while eliminating any competition or rebellion.
Saïx's goals as the Nobody that he was in the end was acquiring a heart and, by extension, Kingdom Hearts. He will do all he can to attain it, even turning on fellow allies without hesitation when they become obstacles, as happened with Axel. His near-obsessive devotion to his goal is his undoing. Throughout the game he repeatedly states his desire to "truly, finally exist", and it turns out his last words are only to Kingdom Hearts, sadly asking for his heart. Indeed, he desires a heart so much that he is even willing to risk staging a rebellion against the undeniably more powerful Xemnas due to knowing fully well Xemnas did not intend to grant him his heart back with Kingdom Hearts, although he displays his caution and intelligence by allying with Axel, another powerful member of the Organization, as he knew he alone could not challenge the Superior. Even then, he seemingly knows better than to fight Xemnas with only Axel and it is implied he intends to use Roxas or Xion as another ally, as he stated in the Reports his plans never counted on both of them leaving. Without Axel, it is likely that Saïx had no other option but to went along with Xemnas's plans until he could develop new but never revealed agenda, which involved him skillfully playing "charades" devoted to Kingdom Hearts but he clearly only saw Xemnas, who never intended to give him a heart, as a means to an unfortunate end.
However, as displayed by Kingdom Hearts 358/2 Days, he seems to still value his friendship with Axel from their time as humans over that which Axel has formed with Xion and Roxas, as was confirmed in the Secret Reports, apparently as he believes that Nobodies cannot form a real friendship without having had one with another beforehand, thus having memories to fall back on. Their relationship seemed to be the strongest, as Saïx entrusted him with his plans for a rebellion and gave him important missions for their plans, all which Axel carried out diligently, but when Xion and Roxas formed a close friendship with Axel, their friendship began to weaken due to how he has no care for Xion as a person and views her as only a tool for their needs and literally Saïx views her as a puppet, and even insists that the others say "it" when referring to Xion rather than "she", which he particularly insists to Axel as he can detect his faltering devotion, further driving them apart. It seemed that Axel already had some discomfort with how Isa had changed after becoming a Nobody even before this, which he stated openly in the Secret Reports and was what led to him to try to isolate himself, to no avail, by befriending Roxas and Xion, indicating although they trusted and were to an extent diligent regarding what they did, their relationship was only a cordial and somewhat mutually benefitting one. His inability to understand why Axel would choose Roxas and Xion over their old friendship only made the strain worse up until it seemed all sorts of friendly feelings between them had vanished, as Saïx showed a cold demeanor when Axel openly showed his betrayal in Hollow Bastion.
In Kingdom Hearts III, while Saïx appears to retain his same personality and goals from his time in the previous organisation, it is revealed that one of the reasons he followed Xemnas was to find out what happened to their other female friend, showing his devotion to his human friends was already sufficient for him to go to endangering extents even when he was emotionless. After being given back his humanity, Saïx showed a better side to himself. He selflessly risked himself by working with Vexen to give Roxas and Xion the replica bodies needed to revive them and showed a more light-hearted side when interacting with Axel and revealing his desire to find their other friend. Although he still seemed to be distant at the idea of Roxas and Xion being Axel's friends, it is clear he did regret how he treated them. As he dies, he reveals that the reason he was so ruthless and berserk when fighting Axel and Sora was because of how he was outraged by how he deemed Axel abandoned him and their other friend on a whim in favor of Roxas and Xion while he remained loyal to the girl they befriended. He made peace with Axel as he returns to being Isa.
Further still, his usual calm and goal-oriented demeanor belies a fierce savagery. In his final confrontation with Sora under the heart-shaped moon of Kingdom Hearts, Saïx becomes a berserk force of destruction. Unlike his reserved manner that is usual of him, he roars, shouts, and attacks relentlessly in battle with no sense of self-control. In fact, Saïx is practically psychotic under the influence of Kingdom Hearts. What this raging state says of Saïx's own emotional capacity is unclear if it's not merely a manifestation of Kingdom Hearts' absorbed power.
Saïx wears a basic Organization black coat along with the usual black gloves and boots. He has long, frayed blue hair framing his face, though slicked back in wild spikes at the top. Behind, it reaches down to his mid-back and is cut slightly neater. A distinctive trait of Saïx's is the X-shaped scar between his yellow eyes that extends to about halfway up his forehead in one direction and to just under his eyes in the other. When Saïx enters his "Berserk" state, his eyes turn completely yellow, his scar becomes more jagged and a bit larger, and his hair becomes much messier. No matter what state, he wears a single studded earring on each pointed ear.
Saïx's transformation under the moon's power is a possible reference to several things, including: the ancient belief that the moon caused madness, hence the term "lunatic"; the modern belief that the phases of the moon can affect a person's mood; the legend of the werewolf, humans who became savage beasts under the influence of a full moon; as well as the berserker warriors of the Norse, who wore clothes made from bear skins as they went into battle in an insane fury and are the source of the modern term "berserk".
A data recreation of Saïx can be fought during the New Organization XIII Event in the month of July.
Saïx plays a relatively important role in Kingdom Hearts 358/2 Days. He assigns Roxas his missions in The Grey Area at the Castle That Never Was, and is present when Xion joins the Organization. He remains in this station throughout the beginning and middle of the game, giving Roxas and the other members missions and also being the one who issued Roxas's promotions into higher ranks and giving him the rights that came with it.
Saïx is the one who gave Xemnas's orders to Axel to eliminate traitors of Organization XIII in Castle Oblivion. It is generally accepted by the remaining members that at this point the two planned to not only eliminate traitors, but also anyone who stood in the way of their plan, such as Vexen and Zexion. Saïx is also revealed to be the one who picked which members would be going to Castle Oblivion, namely the members suspected of being traitors, as well as anyone else who was "getting in the way".
After Axel's return from Castle Oblivion and the growing friendship between Axel, Roxas, and Xion, a rift between Saïx and Axel begins to form. They had been planning to take over the Organization, knowing Xemnas's true plans are not to give them back their hearts, but ever since Axel befriended Roxas and Xion, he is quick to figure out Axel's devotion to their goals as starting to waver, starting from when Axel went out of his way to ask for Xion and Roxas to work together, which Saïx knew obviously something was wrong but he clearly couldn't understand Xion had lost her keyblade and her partnership with Roxas was to buy time until she could regain it, which is seemingly enhanced by how Axel didn't seem to care about capturing Hearts when he suggested he be sent to Agrabah to take care of a Heartless. This is make further worse by how Axel clearly disapproved of the way Saïx treats Xion due to his view of her as being nothing but a mere hooded puppet and even insisting that the others refer to her as "It". He eventually confronts Axel over it and asks he choose between their real friendship or the one Saïx personally considered to be false, even calling him by his real name, leaving Axel more conflicted. By the time of Roxas's departure from the Organization, Saïx dismisses his previous plans with Axel as "just an idle fantasy", as both have changed.
Working on Organization XIII's plans for Sora with Xemnas, when Roxas tries to escape, Saïx confronts him and states the Organization doesn't accept resignations, which Roxas doesn't care and bluntly tells that he has nothing to say, and the two do battle. Roxas comes out on top but Saïx remains conscious and alive. After Xion's end, Xemnas orders Saïx, who no longer remembers her, to retrieve Roxas, who is on his way to the Castle That Never Was to defeat Organization XIII and free Kingdom Hearts, because he believes it will resurrect Xion. While not confronting Roxas himself, it is possible that Saïx was the one who sent the Neoshadows after Roxas, who destroys the Heartless easily.
Saïx's first appearance is in Hollow Bastion, along with the surviving Organization members, excluding Axel, to taunt Sora. He remarks "You're doing well", but like the others (except for Xigbar), does not confront Sora, and simply stands next to Xemnas with his hood down.
Upon Sora's second visit to Twilight Town, the trio fight off several Nobodies that were attacking Seifer and his gang. After they save him, Saïx appears before them, applauding their battle skills. He warns them of a traitor in the Organization: Axel, and he says that he might be in Twilight Town somewhere. Sora insults the Organization, remarking on how they're "not a very organized Organization". Saïx is unfazed, and tells Sora to watch his back, for Axel will stop at nothing to turn him into a Heartless. Sora declares he is not worried, prompting Saïx to remark that the Organization would want nothing to happen to Sora. He also cryptically remarks that the Organization knows how to "injure a heart". He then opens a portal of darkness behind him, and Sora thinks of jumping in after him, though Saïx overhears this and advises not to do so, lest he end up like Riku.
Sora inquires as to what he means, but Saïx immediately leaves to report to Xemnas that he succeeded in placing Sora in a state of confusion and frustration to keep him going toward their goal. Saïx also states that Axel may prove a thorn in their side, which leads to Xemnas giving him orders to deal with the renegade. By the events of the Heartless Invasion at Hollow Bastion, it is revealed that Saïx kidnapped Kairi from Axel. Arriving to interrupt Axel and Sora's conversation, the former fleeing, Saïx ensures that Axel will be rightly punished while playing with Sora's feelings over Kairi by having get onto his knees and beg at the Nobody's feet.
Seeing Sora's devotion, Saïx sees this as a further opportunity to enrage and confuse Sora by eliciting the boy's fury upon refusing to take him to Kairi. Conjuring Heartless, Saïx reveals the Organization's goals to have the hearts held within Emblem Heartless be released by the Keyblade, so that they may flock to Xemnas's synthetic Kingdom Hearts and complete. Despite Maleficent's interference, Saïx has the Dusks he summon subdue her so he can force Sora into defeating more Heartless and release more hearts. But before he can finish his ploy, Maleficent conjures a portal of darkness to spirit Sora and his group away.
Do you feel it? The moon's power!Saïx during his last battle
Later, as Sora makes his way to the Castle That Never Was, Saïx visits Kairi in her cell while making her feel guilty by revealing that she is the "fire that feeds Sora's anger." However, prior to fading back into Kairi, Naminé breaks her original self from her cell and attempts to take her to safety. But Saïx attempts to block the girls' escape before Riku, still cloaked and in the form of Ansem, Seeker of Darkness, attacks him from behind. Saïx does a back flip in the air, and lands a few feet away. Riku slams him up against the wall, intending to finish him once and for all. However, Saïx opens up a portal behind him and sinks away into the wall with a smirk.
Welcoming Sora to the castle, Saïx looks lovingly upon Kingdom Hearts while telling Sora that Kairi no longer needs him and is with a "friend from the darkness". Saïx also states that the Organization's Kingdom Hearts is nearly done, summoning more Heartless for Sora to destroy. Though he notices that Maleficent has also infiltrated the castle along with Pete, Saïx takes this in stride as he vanishes see Xemnas. Once having permission to kill Sora as Xemnas deems their Kingdom Hearts complete, Saïx smiles savagely and remarks that he's waited so long to hear that.
Awaiting Sora and group in Addled Impasse, Saïx calls Sora by the name of "Roxas", saying only he could have made it this far, though Donald vehemently states that he is Sora. Saïx seems not to care, simply stating: "Different name, same fate." Then, summoning his Lunatic claymore, he creates a potent shockwave that pushes Kairi and Riku back towards the entrance of the room as he quickly erects a force field to Sora, Donald, and Goofy for the final time while using the light of Kingdom Hearts to become a berserker. However, despite the incredible power and abilities Saïx is overcome. Defeated and mortally wounded, he limps away from Sora to the ledge overlooking the moon. With the last of his strength, he asks: "Why... Kingdom Hearts... Where is my heart?" All his power gone, he now fades back into darkness. Sora watches with a brief look of pity and regret, then turns to rejoin Kairi and Riku.
Saïx makes his appearance towards the end of the game, when Lea saves Sora from Master Xehanort in Where Nothing Gathers, revealed to have underwent the process of becoming a Xehanort clone by being infused with a part of Master Xehanort's heart. Xigbar calls out to Master Xehanort, who smiles, and Saïx leaps into action, summoning his Claymore in the process. The two former friends have a brief "fight" until Lea jumps out of the way with the comatose Sora. Saïx then flees along with the rest of the Real Organization XIII from The World that Never Was.
Saïx returns with the other members of the real Organization XIII who were from the present. He was first seen talking with Vexen, stating that he was surprised that he wanted to join them but welcomed him into their ranks nonetheless. It was revealed, however, that the two are working together to secure replica bodies for Xion and Roxas.
In Twilight Town on the day before the Second Keyblade War, Saïx appears before Lea through a corridor of darkness, who is sitting on the clocktower. Saïx invites himself and sits next to Lea, saying that he wasn't there to fight and takes an ice cream. When Saïx asks why he bought three, Lea was unable to respond. Saïx starts reminiscing when they were apprentices under Ansem the Wise in Radiant Garden to rescue a girl. He blames Lea for giving up, though Lea argues against it, because he assisted Saïx in climbing up ranks to get closer to Xehanort's Nobody to find out what happened to her. Even though Saïx believes that she and Roxas are gone forever, Lea promises he will get all his friends back, including him. Saïx notices Lea's upside-down tear markings missing, which have stopped him from crying. Lea then scoffs and claims he doesn't need them anymore. Before Saïx disappears, Lea promises to beat and then bring him back the next day during the final battle, which causes him to dryly laugh.
Saïx later appears in the Keyblade Graveyard, walking with the rest of the Organization as they confront the Guardians at the crossroads of the Keyblade Graveyard. After Master Xehanort creates the Skein of Severance, the Organization begin their clash with the Seven Guardians of Light. Saïx and a hooded Keyblade wielder (later revealed to be Xion), clash with Lea and Kairi, with Saïx founding himself matched with Lea, the battle seemingly even, if not slightly leaning towards Lea. When Sora came in to aid them, Saïx proceeds to activate Berserk Mode and overpowers them with Xion's help. As Sora and Kairi are almost finished off by Saïx, Lea attempts to defend them, demanding Isa to stop fighting but is pushed back. Suddenly, Xemnas appears and condemns Lea for betraying them when he used to eliminate traitors. He almost finishes off Lea until the hooded Keyblade wielder stops him, claiming they need him alive. Xemnas clarifies saying they only need his heart, not his soul, and since they were former friends Xemnas passes on the task. Despite being beaten and injured, Lea wanted to know who the hooded figure is, who struggles to strike him down. Sora decides to calmly intervene, pleading and reassuring the figure whom he refers to as "Xion", who becomes overwhelmed with emotion. Unsatisfied, Xemnas kicks her, pulling back her hood revealing her face, causing Lea's memories of Xion to surface. As Xemnas attempts to kill Xion, Lea tries to stop him by hugging his leg, but is unable to stop him. A heart then escapes from Sora and Roxas suddenly reforms, much to Lea's joy.
However, Xemnas kidnaps Kairi and leaves the four to fight Saïx. Xion tells Lea to rest due to his injuries; Roxas and Xion fight along Sora's side against Saïx and despite his best efforts, Saïx is defeated. Lea goes over to him and Saïx bitterly asked why he appears sad, remarking that he thought Lea didn't need the markings under his eyes as it looked like he needed them. Lea is disgusted at that Saïx let the Organization reduce him to this state and says he thought everything was for their missing friend. Saïx confirms that he did sacrifice everything to find her but seeing Axel made friends with Roxas and Xion and abandon him and their missing friend infuriated Saïx beyond all reason, causing him to lose all sense of purpose. Lea, feeling guilty for this, notes he did not forget them and Saïx sadly agreed that Lea wouldn't be that type of person, admitting that he was jealous of Lea's new friendship with Roxas and Xion. After making amends with his friendship with Lea, Saïx fades away.
Saïx, fitting his status as Xemnas's second-in-command, is perhaps the second most powerful member of the Organization 13 just under Xemnas himself. His power is shown by how he is able to survive a fight with Roxas and remain conscious while Axel, who had defeated Xion with some of Roxas's power, was left unconscious from the battle, and he later challenges Sora, Donald and Goofy by himself, proving to be one of the most difficult bosses due to his might, before being defeated. His mere arrival on Hollow Bastion alone was able to intimidate Axel into fleeing. In Kingdom Hearts III, his power has rose to the point of overwhelming Sora, Kairi and Lea with aid from Xion and was later able to stand up to Sora, the dual-wielding Roxas and Xion before being beaten, remaining among the most difficult of bosses in the game.
Although he appears calm and collected throughout when speaking, in battle he becomes a wild, dangerous opponent. Be as wild and savage as he may be, he is an excellent fighter with his large Claymore, wielding it with great skill to perform powerful combos and while he primarily uses his brute strength to compliment his attack, which causes his blows to be somewhat slow despite the strength of it making up for the lack of speed, he is also capable of being swift and agile, quickly landing 3-hit combos and effectively employing jump-strikes, and adept at defense. Even without his Berserk Mode, due to his skills with his weapon, strength and surprising swiftness and agility, he remains a formidable threat and diligent defense is needed in his boss fights to exploit his weaknesses. As displayed when he fights without his Berserk Mode against Lea one-on-one in Kingdom Hearts III, his fighting skills with his Claymore could easily match and even pressure Lea using his Keyblade despite seemingly being at a stalemate with Lea, showing superior skills to Xion, who was knocked aside by Axel. Even in his Berserk Mode, Saïx is still capable of fighting skillfully and attacking swiftly with his Claymore, as displayed in his Limit Cut Boss, where he is shown able to close the distance and attack with quick slams and spins of his weapon. Along with that, even without his Berserk Mode active, he could still manipulate the energies of the moon for quite powerful effects, as before beginning to fight Sora and the party, he was able to cast a potent shockwave capable of forcing Riku with the powers of Ansem back when he protects Kairi and erect an impenetrable force-field to cut off Riku from helping Sora and he is seen unleashing blue energy to force back Isa when at an impasse in a weapon lock. However, his true danger is his ability to draw power from the moon to enter a "Berserk Form". Upon entering this form, Saïx's Lunatic Claymore shifts shape and produces a white aura which serves as extra blades and in 358/2 Days his attacks can inflict silence while his aura is able to push back close enemies. Saïx himself grows bestial, with glowing eyes, manic hair, and bared fangs. His strength and speed increase greatly, with him still having formidable skill with his weapon and can unleash powerful and deadly combos, incorporating spinning and swinging maneuvers, and he becomes nearly invulnerable. He is capable of slamming his Claymore into the ground to produce shockwaves and can unleash streams of blue energy by throwing his Claymore, which he does with great accuracy and speed. While absorbing power from the moon, he keeps himself off the ground through levitation. In Kingdom Hearts III, Saïx displays an even more Berserk Form where he gains 4 replicas of his Claymore that he can use to unleash multiple shockwaves at once and throw them down to slam the ground to emit shockwaves. He also proves able to somehow endure Sora's attacks while gathering energy, indicating the moon's energy could shield him to an extent despite still sustaining damage.
However, Sora can pick up any of the Claymores that Saïx releases, allowing him to use Reaction Commands that will knock Saïx out of his berserk state, as well as inflicting significant damage. When knocked out of his berserk state, Saïx will spend most of his time with his arms stretched towards the moon, absorbing its power. At the verge of defeat, he can fill in the Berserker Gauge much faster. In Kingdom Hearts III, the level of charging speed of the Berserk Gauge is about as fast as when he becomes weak in his first boss and it only grows as the fight continues until his ultimate Berserk Form ends but he can be knocked off with each hit.
The Nobodies under his command, the Berserkers, follow his attack style, using brute strength and a large weapon, but share the same weakness as Saïx.
In Kingdom Hearts 358/2 Days, Saïx's Limit Break is also called Berserk. During Berserk, Saïx goes into a berserk stage; he rushes across the field, dealing continuous, devastating damage to enemies that he comes down hitting with his claymore. When the attack button is pressed, he will jump and perform a stronger smashing attack. Each smashing attack is followed up by a shockwave.
During Saïx's Final Limit, Saïx goes into an even more berserk stage; He comes down to attack even more often, and exerts a sphere of his strength straight from himself while in the air before coming down. The shockwaves that come after each attack also increase in range.
Saïx wields a massive blade known as a Claymore. His signature Claymore is known as Lunatic. Despite many dissimilarities to real claymores, Saïx does use a very large, two-handed bladed weapon. His Claymore is decorated with many additives that resemble the Nobody logo, in blues and yellows. When in normal form, Saïx attacks with powerful slashes and combos with the bladed edges.
Although it seems to be a completely different weapon, the Cursed Hammer of the Berserker Nobodies is used in much the same way, and even has the same Reaction Command.
The names of Saïx's various claymores are all references to astronomy or astrology (especially the moon), with the exceptions of Crocea Mors (Latin for "yellow death") in the Japanese version, which is the purported name of Julius Caesar's sword; and Just Desserts, his joke weapon.