Realm of Darkness

The Realm of Darkness (闇の世界) is a realm made up of Darkness in people in every world. As with the Realm of Light, this realm has a Keyblade, Kingdom Key D, which King Mickey had obtained. Kingdom Hearts is found here. This is also the home of all the Heartless and where the most powerful ones can be found.

Kingdom Hearts Birth by Sleep
In the Final Episode, after Terra-Xehanort turns the Keyblade on himself, he falls into a dark portal leading to the Realm of Darkness. Aqua then dives in and sacrifices her Keyblade and armor to save Terra-Xehanort. However, Aqua herself is now trapped in the Dark Realm.

Between Kingdom Hearts Birth by Sleep and Kingdom Hearts
Ansem the Wise, betrayed by his apprentices, was banished into the Realm of Darkness, a realm he calls the realm of nothingness in his reports, due to nothing existing there save for the darkness. While he is in this realm, he learns to use the power of darkness to exact his revenge, but does not allow the darkness to control him as it has controlled his beloved apprentices.

Kingdom Hearts
Sora fights Ansem, Seeker of Darkness and World of Chaos here.

Kingdom Hearts II
In Kingdom Hearts II, Sora, Donald, and Goofy visit the Realm of Darkness after being saved from Saïx by Maleficent in Hollow Bastion, where they encounter a man in a black coat, later revealed to be Riku. Riku leaves behind a box with a picture of Hayner, Pence, Olette, and Roxas and a bar of sea-salt ice cream. In this same realm, the Keyblade reacts to the ice-cream and Sora opens a Gate.

Blank Points
In Kingdom Hearts Birth by Sleep's secret ending, Aqua finds Ansem the Wise sitting on the Dark Margin on the side of darkness. The scene takes place some time after the Kingdom Hearts Encoder exploded in Kingdom Hearts II. Instead of killing him, the machine's explosion transported Ansem to the dark realm and caused him to slowly lose his memory.

Aqua and Ansem the Wise have a conversation about the worlds and how Ansem came to know Sora. This leads Aqua to shed tears of hope, knowing that he would save her and her friends.

Corridor of Darkness
Corridors of Darkness are unpredictable pathways that interlink the worlds in the Kingdom Hearts universe. The Heartless use these extensively to reach other worlds, as do members of Organization XIII, their subordinate Nobodies, and many other characters. These pathways are formed out of Darkness, so it is unsafe for a normal person to travel them, because the constant use of these corridors would slowly corrupt one's heart. One upside to the Darkness in the Corridors is that it provides a faster means of travel than the Gummi Ships.

However, the Heartless, the Nobodies, and the Princesses of Heart don't have to worry about this, since the Heartless already have corrupted hearts, the Nobodies do not have hearts to corrupt, and the Princesses of Heart have hearts made out of pure light. An example of the Princesses of Heart's immunity would be, when Axel was kidnapping Kairi - he took her through a Corridor of Darkness. Kairi was wearing normal clothes, yet she wasn't affected by the Darkness, as her heart was made out of pure light. According to Nomura in the Director's Secret Report XIII, Riku and Mickey also aren't affected by the darkness at all, due to some "secret similarities".

Other characters who have used these corridors include Sora, Donald Duck, Goofy, King Mickey, Kairi, Riku, Naminé, DiZ, Beast, and even Pluto. Of these, only Riku, Naminé and DiZ have been responsible for summoning the portals.

Ironically, in the first Kingdom Hearts, after the face-off in Neverland, Riku's heart was significantly weakened as he carelessly used a Corridor of Darkness to return to Hollow Bastion. Nomura goes further to state that DiZ and the Beast can successfully use the Corridors of Darkness, and perhaps open them, due to their particularly strong feelings. Furthermore, despite Sora having used the Corridors of Darkness several times before, he has not used them frequently enough to allow the Darkness to stain his heart. The influential power of Darkness depends on the strength of a person's heart.

Anyone who has traveled in darkness for too long would show a few physical traits: their skin darkens and their eyes turn amber. This is especially true for Xehanort, whose Heartless and Nobody both have tan skin and amber eyes. In the case of Ansem the Wise and Braig, it is not so severe as they only have amber eyes.

Maleficent is also believed to travel the Corridors, though she does not show the physical changes. This could be due to her trying to command the Darkness, instead of becoming one with it. It is also known that Pete travels the Corridors as well. He is known to be protected from the Darkness by Maleficent's magic.

The Black Coats worn by Riku, King Mickey, and Organization XIII are said to protect wearers from the effects of darkness, and from detection by those who use darkness. Thus, those who wear these coats can traverse Corridors of Darkness without suffering the negative effects.

Dark Margin
The Dark Margin (referred to by Tetsuya Nomura as the Dark Coastline) is a mysterious place in Kingdom Hearts. It is first seen in the "Another side, Another story [deep dive]" FMV.

In Kingdom Hearts II and in Kingdom Hearts 358/2 Days, Roxas converses with Xemnas at the Dark Margin. He talks to Roxas, telling him how much he looks like Sora.

It reappears in the end of Kingdom Hearts II. After defeating Xemnas, Riku and Sora end up at the Dark Margin. Suddenly, after Sora reads a letter from Kairi, a door appears, leading them to Destiny Islands.

According to Another Report, Nomura states that the Dark Margin is "the tip of a world", i.e. the boundary between Darkness and In Between. Sora and Riku were on the coast of the side of In Between, and were looking over the sea in the Realm of Darkness. Having said this, the Door to Light which appeared in the ending scene is reminiscent of a theme which recurs in the Kingdom Hearts series: "No matter how deep the Darkness, a light shines within."

Realm of Darkness
The titular Realm of Darkness (referred as that in the game data) is first seen in Blank Points as the pathway that Aqua follow while lost in the darkness. Here, she encounters a numbers of Darksides. While she is about to give up and let herself be swallowed by the darkness, Terra's and Ventus' Keyblade, the Earthshaker and Wayward Wind rescue her before vanishing, renewing her hopes.

Realm of Darkness: Middle Zone
The Middle Zone is an open area coming right at the end of the pathway. The area is filled with stairs-like terrain, high cliffs, and strange column-like structure with glowing blue marks. There are also strange orbs of darkness that, when approached, will push Aqua away, and are useful for reaching higher areas by jumping on them. It is in this area where the player first encounter the heartless.

Realm of Darkness: Lower Zone
The Lower Zone is a maze-like area, with countless cliffs and twisted pathways populating this zone. In order to advance trough here, it is necessary to make good use of the dark orbs that push you away. There are zones where the pathway is vanished, and just noticeable for a subtle purple glow. For the path to appear, Aqua must defeat the Heartless that spawn near them.

Realm of Darkness: Upper Zone
The Upper Zone consist of various hovering platforms surrounded by twisted, glowing structures. Should Aqua fall in the pits below, she will return to the Lower Zone. The Heartless in this place only spawn once in the places where the ground is purple.

Valley of Darkness
The Valley of Darkness is an open space in the Realm of Darkness. It seems to be covered by a thick mist, and surrounded by twisted, dark trees in the background. It is here that Aqua is attacked by the Hunter of the Dark and engages in a fight with the Heartless. A mysterious vortex is seen in the background, surrounded by dark thorns.

Heartless
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