Saïx

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. He is 23 years old and 5'9" tall man. 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 demises at Castle Oblivion under the guise of Xemnas' 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

for 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 obtain 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 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 he had no other option but to went along with Xemnas' plans until he could develop new one, but it was never revealed the plan, 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.

He was not above all emotions, however, as he took sadistic pleasure in ending the charade at Xemnas’ blessing, and later flashed Sora a decidedly feral grin at the chance to confront him head on.

However, as displayed by Kingdom Hearts 358/2 Days, he seems to still value his friendship with Axel from their time as full beings over that which Axel had formed with Roxas and Xion, 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 quite 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 he even 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 benefiting 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 he showed a cold demeanor when Axel openly showed his betrayal in Hollow Bastion.

In Kingdom Hearts III, as he appears to retain his same personality and goals from his time in the previous organization, 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, he 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 lighthearted side when talking 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 fades away, 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 as 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, he 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 the matter of fact, he is practically psychotic under the influence of Kingdom Hearts. What this raging state says of his 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 Dark Pastel 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 amber 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".