Universes

In the Universes, also called the World, there are many worlds that fall into certain realms. All of these realms are on their own plane of existence. A Universe is also a term used to collectively refer to all the particular characters, stages, items, music, and other properties appearing in the fighting games that are thematically featured in another game franchise.

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 * —About the Universe.

Travel
Travel between the other universal worlds is normally impossible. The worlds are all protected by dimensional barriers that prevent outsiders from entering for the most part. However, these barriers can be broken, resulting in a meteor shower in that world.

Sora use the Gummi Ship to travel between worlds on the World Map, an event that serves as a mini-game between areas. Some worlds require certain special Gummi Blocks to access; for example, a special Navigation Gummi must be installed by Cid to unlock a second set of worlds. Once they reach them, the party can enter and then depart each world through its Save Points.

Three worlds can only be accessed by entering through other worlds and do not directly require use of a Gummi Ship
 * 100 Acre Wood via space-time book in Traverse Town and Hollow Bastion/Radiant Garden.
 * Timeless River via the Hall of the Cornerstone at Dimension Castle.
 * Space Paranoids via Ansem's computer in Hollow Bastion/Radiant Garden.

It should be noted that, there are no Gummi Ships; the worlds Sora visits are recreations from his memories from the first game brought to life on each floor of Castle Oblivion. This is likewise true of wherein, all worlds are recreations of data from Jiminy's Journal.

There are also no Gummi ships, as these sleeping worlds are entered through diving, a mini-game similar in format to the original Gummi Ship mini-game but with some characteristics from the iteration, such as bosses that must be defeated before you are able to proceed to the world.

According to Hawk, the pathways between the worlds are known as the Lanes Between.

There are six known ways to travel through the worlds:
 * Piloting a Gummi Ship; as Gummi Ships are composed of fragments of shattered barriers, they are capable of passing through them.
 * The "Star Shard" that Commander Arthoross took from Jolnir to travel across worlds. The downside to this method of travel is that if the user does not know how to control the shard, the destination and time of activation will be random.
 * Utilizing the Corridors of Darkness; this is a faster means of travel than the Gummi Ships, but those who use them are at great risk of being corrupted or destroyed by the darkness.
 * Teleportation, used by beings that possess powerful magic; Dr. Wily was able to teleport himself, and Sora, from Hollow Bastion/Radiant Garden to Dimension Castle, as well as teleport Cranky Kong to Radiant Garden. Wizeman is also capable of teleportation between worlds.
 * Keyblade Gliders; Terra, Aqua, and Ventus can change into their armored form and turn their Keyblades into vehicles that can travel to other worlds by using the Lanes Between.
 * Time travel, such as used by Ansem, Seeker of Darkness, Young Xehanort, Jolnir and Pete. However, Young Xehanort's method of time travel is trickier than the Jolnir and Pete's; there needs to be a version of himself where he needs to go and he can only go backwards or forwards in time.

Stars
Stars are massive, luminous balls of plasma that are held together by their own gravity.

In the Kingdom Keymasters games, each star is the representation of one specific world. Should a star stop shining, that would mean that particular world has disappeared from existence, most likely from destruction from the Heartless.

In Kingdom Keymasters, many stars disappeared. In Tom's Letter (before Destiny Islands is attacked by the Heartless), He mentions the fact that the stars have been disappearing, one by one, and so he went to find out why. When first arrived at Traverse Town, they discovered a star corresponding Destiny Islands fade out of existence. They were restored after Sora and his friends stopped Ansem's plan to plunge the world into darkness.

In Kingdom Keymasters II Conner Cooper implies that there are stars to represent certain individuals as well, such as when she told young Sly Cooper that all their great ancestors of the Cooper Clan are looking at them in the form of stars. After the raid and attack of Clockwerk and the Fiendish Five, the young Sly tries to reach out to his deceased father, and he appears to him immediately. The same implication happens, when Master Jolnir detects that "Eraqus's star has blinked out", after he was struck down by Master Xehanort.

Realm of Light
The Realm of Light (光の世界, Hikari no Sekai) is a realm made up mostly of light and makes up almost half of the Kingdom Hearts universe, similar to the Realm of Darkness. Like the Realm of Darkness, the Realm of Light has a Keyblade, the Kingdom Key, which chose Sora as its wielder.

Most of the game's worlds are found here, save for those in the Realm of In Between, like Traverse Town, Twilight Town, Castle Oblivion, and The World That Never Was. It can be presumed that most of the Worlds accessible by the Gummi Ship are either within the Realm of Light, or are related to it, like Twilight Town.

In Kingdom Keymasters II, one notable citation had been made by Sora regarding the Realm of Light during the scene of Sora and Riku at the "end of the road" after defeating Xemnas: ''The other side... The realm of light is safe now. Kairi, the King and the others are there''.

Door to Light
The door leading to the Realm of Light is called the Door to Light. It was the door Sora and Riku went through while they were stuck in the Dark Margin. It is not certain what caused the door to appear, though one reason could be, as Riku pointed out at the end of the game, the light within Sora's heart, which was brought out by Kairi's Letter (prior to reading it, Sora had willingly given up hope of returning home).

Its counterpart is the Door to Darkness.

Realm of Darkness
The Realm of Darkness (闇の世界, Yami no Sekai) is a realm made up of darkness and makes up almost half of the Kingdom Hearts universe, its counterpart being the Realm of Light. Like the Realm of Light, the Realm of Darkness also has a Keyblade, the Kingdom Key D, which Commander Arthoross had obtained. Little is known about this realm, save for the fact that it is the home of the Heartless, and Kingdom of Hearts is found within its deepest depths.

Many characters have been in the Realm of Darkness before, the most notable being Aqua, Ansem the Wise, Riku, Commander, Roxas, Xemnas, and Sora.

Door to Darkness
The Door to Darkness is a door in the Realm of Darkness that leads to the deepest, vastest darkness. This darkness can attract an endless swarm of Heartless. Beneath this darkness, however, is the light of Kingdom of Hearts. Sora and Commander Arthoross worked together to close the Door to Darkness in the original Kingdom of Hearts.

Its counterpart is the Door to Light.

Realm Between
The Realm Between is the third realm in the Kingdom Keymasters series, and lies on the boundary between the Realms of Light and Darkness.

Few worlds exist within it, and most have some special nature or purpose. As of now, Traverse Town, Land of Departure/Castle Oblivion, Twilight Town, Mysterious Tower, and The World That Never Was are the only worlds confirmed to exist within the Realm Between. Each world ties closer to the Realm of Light or the Realm of Darkness, with the exception of Twilight Town, which exists exactly in the middle.

Worlds
The World (世界, Sekai) is a location that appears in the Kingdom Keymasters series. Serving as the "levels" for the games, Sora and other characters are charged with visiting and protecting them through the course of the series. By defending the worlds from the Heartless, Nobodies, or other enemies, the series' respective protagonists keep the Darkness from spreading and the worlds from being manipulated or destroyed.

At the end of every world (in the original Kingdom Keymasters) Sora have to fight a boss of that world (which is either a giant Heartless, or a villain) which opens the Keyhole area when defeated. At the end Sora locks the Keyhole and earns a Gummi that will let him go to the next world.

Each world that appears in the Kingdom Keymasters series has its own distinct look, and for the most part hold true to the video games, movies and cartoons they are based on. Often the plot of the game in that world will be based on its original source.

Almost all worlds can be visited in the course of the game and are part of the course; there are exceptions, though, since some places can be seen in cinematic cutscenes but not actually accessed by Sora's party. All worlds are separate from one another, and with only a few exceptions, most people are unaware of the existence of other worlds.

World Characteristics
There are over thirty worlds that have appeared in the Kingdom Hearts series so far. Most of them are based on various animated features and contain locations and characters from or inspired by the films. As a result, worlds are greatly varied in appearance, style, and nature, as their sources range from the oldest to more current canon.

In addition to the Based-on worlds, twelve worlds are exclusives that were created by game developers Square Enix just for the Kingdom Keymasters series. They are not part of the canon, nor Square Enix's games canon, but do tend to be populated with even Square Enix characters, especially from the Final Fantasy series, as well as the occasional Disney character or original characters created just for Kingdom Keymasters.

Some worlds have names that don't seem to accurately reflect what is found there. A famous example is Neverland in Kingdom Hearts; Sora and company get to go through a pirate ship and fly around the Clock Tower, but never actually reach the island where live. To further confuse things, some worlds in Kingdom Keymasters II contain what could almost be considered sub-levels or second worlds within them.

Past
According to the story told by Kairi's Grandma in the Hollow Bastion's Library, long ago, there was one single world that was constantly bathed in the warmth of Light. When people began to fight over the Light within their world, Darkness appeared in their hearts, and the world was consumed. However, fragments of light remained within the hearts of children. From this light, children were able to rebuild the lost world.

However, darkness still existed, which caused the worlds to be separate from each other, divided, waiting for the true light to return. This was explained in more detail in Birth by Sleep, where it was revealed the fight was between the many Keyblade holders over Kingdom Hearts, and eventually led to the Keyblade War.

Prior to Kingdom Keymasters, the worlds were surrounded by barriers, to prevent outside interference, making it impossible for different worlds to have contact. The arrival of the Heartless caused the barriers between the worlds to crumble and disappear, and some worlds were even consumed by the Heartless. Gummi Blocks are actually pieces of these broken barriers.