Ansem, Seeker of Darkness
Ansem, Seeker of Darkness, sometimes referred to as Xehanort's Heartless, is the main antagonist of Kingdom Hearts and the "Reverse/Rebirth" scenario in Kingdom Hearts: Chain of Memories, as well as a supporting antagonist in Kingdom Hearts 3D: Dream Drop Distance. He is a member of the True Organization XIII and the Heartless of Terra-Xehanort, and as such his appearance and personality are primarily derived from Master Xehanort, and he retains his original form's "shadow".
Ansem was created when Terra-Xehanort, masquerading as Ansem the Wise, reawakened his sleeping memories and split his heart from his body, creating a Heartless; this Heartless, also named Ansem, appears to have characteristics of both Emblem and Pureblood Heartless, and it is unclear exactly which category he falls under. However, because Terra-Xehanort did this of his own will, he retained his memories in his new existence, and gained the ability to control the other Heartless. With their power, Ansem attacked the Realm of Light, intending to have the Heartless consume the hearts of every world and lead him to Kingdom Hearts.
 Before Kingdom Hearts Birth by Sleep
On a quest from his original persona, Ansem travels through time to find Xehanort's younger self on Destiny Islands, before he had become a Keyblade wielder. Ansem spurs Xehanort onto his path towards darkness, and passes on his ability to time travel so that Xehanort can complete his own mission: gathering twelve other incarnations of Xehanort into an organization so that, together, they could create the χ-blade and restart the legendary Keyblade War. Afterward, Ansem returns to his own time to enact the next phase of his plan.
 Between Kingdom Hearts Birth by Sleep and Kingdom Hearts
Terra-Xehanort, at the time using his king's name, "Ansem", willingly gave his heart to the darkness in the pursuit of knowledge, creating both his Heartless and his Nobody, Xemnas. His Heartless was able to retain its selfhood for uncertain reasons, though it was believed by the first Ansem that this was due to Terra-Xehanort's willing abandonment of his heart. By casting off his body, Ansem also gained the ability to travel through time.
The self-styled "Seeker of Darkness" and the legions of Heartless at his command continued Xehanort's pursuit of knowledge in the belief that it lay with darkness, and stole countless hearts from both humans and worlds in their search for their ultimate goal, a legendary repository of tremendous power and knowledge known as Kingdom Hearts. To reach this heart of all worlds, Ansem would need to open the Final Keyhole, and to do that, he would need the Princesses of Heart to complete it first. He also realized that he needed to locate and neutralize the wielder of the legendary Keyblade, to prevent them from saving the worlds from his Heartless. Believing that the Princesses and the Keyblade wielder are connected, he sent Kairi, a Princess of Heart living at Radiant Garden, to a world where a future Keyblade wielder lived.
As he waited for his theory to be validated, Ansem traveled through time to Destiny Islands and completed his mission with the young Xehanort, then returned to his own time.
 Kingdom Hearts
Ansem, after nine years of being a Heartless, appears in a brown robe at the Destiny Islands Keyhole before the world's fall into darkness, insulting Sora's ignorance of what was to come, and completely ignoring Sora's questions.
The villain appears again to Riku, after his loss to Sora at Hollow Bastion. Shaken by his loss of control over the Keyblade to Sora, Riku lets himself be influenced by Ansem and his promise of power. Riku then lets his heart open up to the darkness, allowing Ansem to possess him.
Firmly in control of Riku's body, Ansem creates the artificial Keyblade of People's Hearts from six of the Princesses of Heart's hearts. This Keyblade possesses the power to unlock hearts, a property he soon tests on Maleficent, transforming her into a gigantic dragon. The dragon is felled by Sora and his friends, leading the Heartless to comment that the dark fairy was arrogant to believe that she manipulated the Heartless when it was actually the other way around. He insults Maleficent and takes his leave, waiting for Sora in the chamber of the Final Keyhole.
Sora arrives, finally reunited with Kairi, though she is comatose due to the loss of her heart. Ansem comments that she lacks a heart, and from his impersonal comments and unusual nature, Sora realizes that who he sees as Riku is not truly the friend he knew. Riku introduces himself as "Ansem, Seeker of Darkness". The Heartless goes on to explain that Kairi's heart is in Sora, and that his dark Keyblade is necessary to remove the imprisoned heart. Sora refuses to agree with the plan and they battle. Sora wins the duel, and Ansem retreats. However, his efforts are not in vain, as Sora stabs himself with the dark Keyblade, in order to free Kairi's heart as well as the six other Princesses. This ends up opening the final Keyhole and the way to Kingdom Hearts, as well as the loss of Sora's heart and his brief transformation into Sora's Heartless.
Ansem shortly returns, having expelled Riku's heart and shaped his body into one resembling his original human self. Now that the final Keyhole is open from Sora's sacrifice, he plans to kill Kairi now that her purpose in his plans has been fulfilled. Donald and Goofy bravely make a stand against Ansem in order to protect Kairi, but both know that, without Sora, they may not be able to stop him. Before he can dispose of the three, Riku projects himself from Xehanort's stolen body and manages to establish enough control to stop the Heartless in his tracks, allowing Donald and Goofy to escape with Kairi. This leads to an internal struggle between the two that Riku ultimately loses. His heart is forced out of his body, and Ansem completely takes control. Ansem then allows himself to be enveloped by the darkness flowing out of the Keyhole, and travels to the End of the World and Kingdom Hearts.
As Sora, his humanity having been restored by Kairi's light, arrives at the remnants of Destiny Islands at End of the World, Ansem appears, bearing Riku's form. He explains Riku's fall to darkness, that he desperately sought to escape the island "prison" enough to open his heart to darkness. Afterward, Ansem explains his philosophy: that worlds and hearts begin and end in darkness. Thus, darkness is the heart's true essence. Sora denies this, in words and in battle, with Ansem. During the battle Ansem summons both his familiar, the Guardian Heartless, and a Darkside Heartless to assist him. As the battle rages on, Ansem leads the trio to the endless abyss where the Door to Darkness resides. This time, Ansem merges himself to the World of Chaos, a monstrous Heartless ship, and captures Donald and Goofy, though Sora rescues them.
After several more rounds of combat, Ansem, weakened, opens the Door to Darkness, imploring Kingdom Hearts to fill him with the power of darkness so that he can gain enough power to destroy Sora, Donald, and Goofy and shroud the universe in darkness. However, Ansem is horrified to see light pour out of the door. The overwhelming light of Kingdom Hearts envelops and destroys Ansem, allowing Riku to take back his body.
 Kingdom Hearts: Chain of Memories
However, because Riku served as the host for Ansem, a piece remains even after his destruction by the light of Kingdom Hearts. This bothers Riku greatly, who ends up in Castle Oblivion thanks to his heart resonating with Sora's, who is also in the castle.
Guided by a mysterious voice, Riku climbs through the basements of Castle Oblivion, trying to rid himself of his darkness. However, Ansem appears early on, intending to overcome Riku, but fails. Still, Ansem remains, and even stirs the darkness in Riku's heart so that he may use it in battle, if he so chooses. The dark being remains confident that Riku will eventually give into the darkness.
At times, Riku almost becomes overwhelmed by the darkness, but King Mickey's light continually comes to the rescue, frustrating Ansem. Eventually, Riku overcomes his fear of the darkness, intending to use it as well as the light. He also additionally receives some guidance from the enigmatic DiZ, the true owner of the mysterious voice, who in turn leads Riku to Naminé. Naminé offers to seal away Riku's darkness and Ansem, but he instead chooses to face the Heartless on his own. DiZ then gives Riku a card that will give Ansem form, so that Riku can finish him off once and for all.
Ansem again tries to turn Riku to the darkness completely, and tries to defeat the young boy so that he can take over again. However, though he is defeated, Riku realizes that Ansem still lingers in his heart, and sets off with King Mickey in order to rid himself of the Seeker of Darkness forever.
 Kingdom Hearts 358/2 Days
Within Riku's heart, Ansem's darkness starts to eat away at him, forcing the boy to wear a blindfold to put a stop to Ansem's false visions. This comes to a head when DiZ sends Riku to capture Sora's Nobody, Roxas, so that the two can join and Sora can awaken from his slumber. Riku catches up to Roxas at The World That Never Was, but Roxas proves to be too powerful and Riku is left with only one way to overwhelm the Nobody: unleashing his inner darkness. This allows Riku to manifest Xehanort's powerful guardian, who seizes Roxas and knocks him unconscious, but also forces Riku to take on Ansem's appearance. Feeling that he has sacrificed his identity, Riku takes on Ansem's name.
 Kingdom Hearts II
During the Battle of the 1000 Heartless at Hollow Bastion, King Mickey reveals the truth about "Ansem" to Sora, Donald, and Goofy—the Heartless wasn't the real king of Radiant Garden, but the Heartless of an impostor. While the trio are shocked and dismayed to learn this, Mickey pacifies them by telling them that Ansem still needed to be stopped.
Following the destruction of the Kingdom Hearts Encoder Ansem the Wise was using, the resulting explosion of light restores Riku to his normal form, implying that "Ansem" has finally been destroyed and his hold on Riku broken once and for all.
 Kingdom Hearts coded
Yen Sid later explains to Mickey that the destruction of both Ansem and Xemnas has revived Xehanort and will lead to the restoration of Master Xehanort. Ansem appears along with Xemnas as one of Mickey's mental images.
 Kingdom Hearts 3D: Dream Drop Distance
Ansem returns to become part of Master Xehanort's new Organization XIII, thanks to Young Xehanort's doings while time travelling. Accompanied by Young Xehanort, Ansem appears before Riku in La Cité des Cloches, stunning the young Keybearer, and offers him to become part of the darkness again, but Riku protests, reminding Ansem that he now walks the road to dawn. Undaunted, Ansem merely takes his leave.
When Sora is captured in the World That Never Was, Riku rushes to his rescue and runs into Ansem again. Ansem reveals that Riku had been traveling within Sora's dreams like a Dream Eater, and asks Riku to join him now that the boy has accepted his darkness. As they fight, Riku counters by asking Ansem to become part of his light, but Ansem ignores him and is eventually forced to retreat.
Once Riku finds Sora in the throne room with Mickey's help, Ansem appears before them along with Master Xehanort, Young Xehanort, Xemnas, Xigbar, Saïx and the rest of the new Organization. Master Xehanort proceeds to reveal that Ansem's possession of Riku's body, along with overseeing Maleficent's gathering of the Princesses, was all part of his master plan with Riku meant to become the vessel to complete the Organization. Ansem physically restrains Riku from trying to save Sora from becoming Master Xehanort's final vessel, but Lea's unexpected intervention distracts Ansem long enough for Riku to break free. Ansem summons his Guardian and has it grab Riku and Mickey, but the Guardian is defeated by Donald and Goofy. As the heroes advance, Ansem retreats with the rest of the Organization, returning to his rightful point in time.
 Other appearances
Before possessing Riku, Ansem was little more than a wandering heart and could only appear as a figure in a brown hooded robe. This robe has two dark brown straps crossing over his shoulders and chest with five metal studs lining either strap. Due to his lack of a body, he appears much shorter and crippled in this form and wears the robe's hood up to hide his lack of a face.
Like his Nobody counterpart, Ansem's skin color varies by being depicted as tan in the game to quite dark in official artwork. He shares Xehanort's amber-orange eyes and long white hair, as well as the three spikes on the top and sides of his head, but he lacks Xehanort's bangs.
He wears silver-white gloves on his hands, each with a grey band on the wrist, while the rest of the glove, which has three black buttons lining one side, bells outwards. There is a black pauldron on both of his shoulders, each attached to his coat by two straps. He also wears black pants and black, silver-lined, knee-high boots identical to the ones worn by Organization XIII members. On the Heartless's chest is the Heartless emblem, but it seems that it is not part of him, as when Ansem creates the World of Chaos, he loses both of his jackets and his gloves, and the emblem transfers to the World of Chaos. He also grows to a tremendous size and his eyes become completely orange in this form.
Ansem's black leather coat is red on the inside and lined with yellow, and also has a large grey section that covers the lower half and shoulders of the coat. Upon closer inspection, this grey section seems to be attached by several small pins or buttons around the hip and neck sections of the coat, as well as by a belt that wraps around the Heartless's back and attaches to the rim of the coat. This coat is high-collared and completely unzipped, showing the second, shorter jacket the Heartless wears underneath. Ansem's second jacket is white and high-collared much like the outer coat. It is mostly unbuttoned and exposes Ansem's chest before being closed up by three buttons and two belts near the Heartless's waist, only to flare outward again, leaving three buttons undone. When seen cloaked, Ansem appears to be shorter and more crippled.
As Ansem is essentially the Heartless of Master Xehanort, his overall appearance is nearly identical to a younger version of Master Xehanort, wearing the elderly Xehanort's attire.
Ansem is, thus far, one of only three Heartless with human-level intelligence, the others being Sora's Heartless and Scar. His knowledge of the worlds and hearts shows that Xehanort's keen intellect has survived the transition into a Heartless. However, the few shreds of humanity which remained in the researcher have been obliterated. Ansem is cold, calculating, and utterly ruthless. He treats people and their hearts as either tools to be manipulated and disposed of, or as cattle for his ravenous Heartless legions. He reveres power and knowledge above all things, and he despises ignorance.
The only times when Ansem's voice rises above a cold, monotonous drone is when he is berating Sora for his foolishness, or when he is reveling in his latest triumph. However, Ansem's scientific genius is blinded by obsession with the darkness. His arrogance ultimately leads to his destruction when the door to Kingdom Hearts is opened, and his greatest thesis is, in the end, proved wrong.
Kingdom Hearts Birth by Sleep reveals that Ansem is essentially the Heartless of Master Xehanort. This is why he appears to share most of his personality traits with the elderly Keyblade Master, demonstrated by his choice of words when facing Sora, Donald, and Goofy; this is also reflected in his desire to find, open, and become one with Kingdom Hearts itself.
As a Heartless, Ansem has control over darkness, which he can use to attack others, steal hearts, and create Corridors of Darkness. He can also possess other beings, and has command over the Guardian.
Ansem does not wield a specific weapon.
While possessing Riku in Kingdom Hearts, he wields the Keyblade of heart, which was created from the six captured hearts of the Princesses of Heart. Later, in his World of Chaos form, Ansem wields a weapon as massive as he is, a dual-bladed Soul Eater.
When fought on his own, Ansem simply uses the power of darkness and his Guardian to attack opponents. When Riku assumes Ansem's form to become Riku-Ansem, he wields his Soul Eater (and later the Way to the Dawn), just as he does normally.
 See also
 Notes and references