Universe of Kingdom Hearts

The Kingdom Hearts video game series, developed by Square Enix in collaboration with Disney, takes place in an unnamed fictional universe with numerous self-contained worlds based on intellectual properties from both companies. Many of these worlds are based on animated Disney movies, though Kingdom Hearts II introduced worlds based on live-action Disney films as well. In addition to the Disney worlds, a number of original worlds appear over the course of the series. The series centers around the main character Sora's search for his friends and his encounters with Disney and Final Fantasy characters on their worlds. The first game, Kingdom Hearts, takes him through each world to lock their keyholes and prevent the Heartless from destroying them. The sequel Kingdom Hearts: Chain of Memories takes place in Castle Oblivion, where he visits memory-based simulations of many of these worlds that are generated on-the-fly as he travels through them. In Kingdom Hearts II, Sora helps the residents of these worlds again in search of his friend Riku. The Kingdom Hearts games have been both critically acclaimed and commercially successful and the design of the worlds has been praised for its faithfulness to the source material.

Concept and design
The Kingdom Hearts games are divided into various game levels, referred to as "worlds", which the player progresses through over the course of each game. Worlds vary in appearance, typically dependent on the Disney setting which they are based on. The worlds' graphics resemble the art style from the originating Disney film and the worlds are inhabited by characters from their respective films; for example, Hercules and Philoctetes appear in Olympus Coliseum from Hercules, while Aladdin, Princess Jasmine, and the Genie appear in Agrabah from Aladdin. The game worlds consist of interconnected field maps where battles and plot-related events occur. Players travel from one world to another via a Gummi Ship, or in Kingdom Hearts Birth By Sleep, characters travel via "keyblade glider". In 358/2 Days, Corridors of Darkness are used. Worlds created specifically for the game mirror the overall appearance of the other worlds and predominantly feature characters from Final Fantasy games and original characters.

Though Disney gave director Tetsuya Nomura freedom to choose which characters and worlds would be used in the games, he and his staff tried to stay within the established roles of characters and boundaries of the worlds. Nomura found managing and keeping consistent multiple worlds to be problematic. After determining the number of worlds in the universe, Nomura picked ones he felt would fit into the series' scenario. The list was then evaluated by his team and finally by Disney representatives. Nomura tried to maintain the same number of worlds in each game and made an effort to minimize any overlap in the overall look and feel of each world. He and his staff accomplished this by categorizing various Disney worlds by appearance and setting. For example, a world based on The Jungle Book was considered for the first game, but was omitted due to its similarity to Deep Jungle from Tarzan. They also tried to take into account worlds with Disney characters that would be interesting. For example, Nomura chose to include a Mulan world for its unique atmosphere. The Tron world's design was meant to emulate an old computer game. Nomura got the idea to include this world after seeing a Disney employee working on Tron 2.0. He hoped that the fact that it was so different from the other worlds would make it enjoyable to players.

Common elements and basic concepts
Nomura intended hearts as well as the strengths and connections of the heart to be a common theme in the games. Characters within the Kingdom Hearts series are composed of three parts: body, soul, and heart. The body acts as a vessel for the heart and soul, with the soul giving life to the body. The heart holds their memories, and gives them emotion, light, and darkness. When darkness consumes a character's heart, they become corrupted and turn into Heartless; a Nobody is created from the remaining body and soul, when the victim is of strong heart and will. Heartless act as forces of darkness, seeking to consume more hearts, including those of worlds. In addition, it still appears that people can "die" like normal if not transformed into a Heartless. Disney's Hades rules over the afterlife—or, more accurately, the underworld—where the deceased of various worlds seem to end up, including Auron from Final Fantasy X.

The Kingdom Hearts universe is divided into planes of existence called "realms". Most of the series takes place in the "realm of light". Opposite the realm of light is the "realm of darkness", where Kingdom Hearts resides and where Heartless are born. The "in-between realm" is a plane where Nobodies come into existence. As well as these known realms, Ansem the Wise was banished to a "realm of nothingness", which he described as a realm "where all existence has been disintegrated".

Heartless and Nobodies
The Heartless (ハートレス) are hearts corrupted by darkness, lacking a body or soul. They are named "Heartless" for their total lack of emotional capacity and are the most common type of enemy the player encounters in the Kingdom Hearts games. Originally there are only "Pureblood" Heartless, black shadow creatures that lack hearts who were born of pure darkness, and usually exist in the realm of darkness, rarely appearing in realm of light. However, the experiments by Ansem the Wise and his apprentices into the capacity of the heart lead to the seemingly unintentional creation of Heartless in the Realm of light.

While researching these Pureblood Heartless, Xehanort and Ansem's other apprentices devise the means to create artificial "Emblem" Heartless via the corruption of living hearts. Unlike Purebloods, which dissolve into black smoke when defeated, Emblem Heartless release hearts once defeated. However, unless the Keyblade is used to defeat the Heartless, the stolen hearts go to the realm of darkness where they turn into Heartless again. Ordinarily, the Heartless are mindless and function on instinct, but obey those with strong will. However, in worlds closer to darkness, the Heartless are stronger and become uncontrollable. They invade worlds through corridors of darkness, which are unpredictable pathways that interlink the many worlds.

When Heartless are created, the body and soul of those with strong hearts that have lost their hearts to darkness may become another type of creature called a Nobody (ノーバディ). As they lack hearts possessing light and darkness, they are "nothing", yet still exist within the Kingdom Hearts universe. Unlike Heartless, Nobodies are able to attack with definite planning. Members of Organization XIII, a group of Nobodies central to the plot of the series, keep their human form because they possessed strong hearts as humans and thus remember their original existence. However, if they lack memories, such as weaker Nobodies, they assume malformed, inhuman shapes. Most members of the Organization control one type of Nobody suited to their fighting style.

Like the Emblem Heartless, Organization XIII and the Nobodies have an insignia—an upside-down, incomplete heart—which was designed to look like a splintered heart as a complement to the Heartless emblem. However, upon being defeated, a Nobody fades into a state of non-existence until its Heartless counterpart is destroyed with the captive heart released, recreating the original being they were splintered from.

The world of the Heartless, End of the World, appears natural due to their instinctive nature, while the Nobody world, The World That Never Was has a city and castle, symbolising their ability to think and plan. Nobodies also appear to be stronger than most Heartless as Dusks(the most commen form of Noboddy's) can easily slay Soldiers(the most commen form of emblemed Heartless) without much effort.

The Heartless emblem appears to be based on the X-blades keychain while the Nobodies' is based on the Mark of Mastery (the emblem Eraqus, Terra, Aqua and Ventus wear).

Unversed
The Unversed (アンヴァース) are creatures that appear in Kingdom Hearts Birth by Sleep, prior to the Heartless and Nobodies within the continuity. Being extensions of Vanitas that feed off the negative emotions of people, the Unversed are used by Master Xehanort as the foundation of his master plan to obtain the ultimate powers of darkness. It appears boss-level Unversed can be created when they feed off the negative emotions of someone, without the help of Vanitas, as Symphony Master and Cursed Carriage appeared when Lady Tremaine grew jealous or angry with Cinderella. The Queen also turned the Magic Mirror into an Unversed using one of her potions (or darkness in the Japanese version). The Unversed cease to be after Vanitas integrates back into Ventus and is subsequently destroyed within Ventus's subconscious. The Unversed are described by Nomura as being "those who were not well-versed in their own existences."

Bugs
Kingdom Hearts coded sees the inclusion of software bugs, simply referred to in-game as "bugs", as the game's main antagonistic force. These bugs appear after the contents of Jiminy Cricket's journal are digitized, corrupting the data therein, as an unintentional side-effect of Naminé leaving an extra message inside the journal for Sora and his friends to investigate. They primarily take the form of "Bug Blox" (バグブロックス), which are cubes that the game's main protagonist, a virtual replica of Sora called Data-Sora, can destroy or use as platforms. There are several different varieties of Big Blox, the most common, breakable variety being black-and-red in color. Other bugs take the appearance of Heartless that Sora had defeated in Kingdom Hearts. The original bug responsible for corrupting the journal's data takes the form of Sora's Heartless, and displays sentience as it tries to delete all of the data inside the journal. While its most basic form is the weak and common "Shadow" variety of Heartless, it grows increasingly powerful to the point where it takes other forms, such as an entirely black lookalike of Sora with yellow eyes, or a gargantuan variety of Heartless called "Darkside". The bugs cease to be after Data-Sora destroys the original bug and resets the entire datascape.

Dream Eaters
Dream Eaters (ドリームイーター) are the main enemies of Kingdom Hearts 3D: Dream Drop Distance. Like the Heartless, they are created from darkness and are compelled to find the keyholes of worlds. In contrast to the Heartless, however, Dream Eaters originate from the darkness created in worlds that are in a state of "deep sleep" and are isolated from other worlds. Though Dream Eaters usually manifest as "Nightmares", creatures that devour good dreams and create bad ones, there are also "Spirits" that do the opposite and function as Sora and Riku's partners.

Keyblades
Keyblades (キーブレード) are key-shaped weapons created to combat darkness and are currently the only thing that can free hearts from a Heartless form. Keyblades also have the ability to lock and unlock all manner of doors and keyholes. A Keyblade changes in both appearance and strength with different keychains, which augment its wielder's fighting capabilities; some can be obtained as a result of in-game events, while others can be obtained by completing mini-games. A driving element to the first game is the ability to seal the "heart" of a world by locking the keyhole to the door leading to it, preventing it from being destroyed by Heartless. In Kingdom Hearts II, the player uses the Keyblade to unlock pathways between worlds that were closed after the events of the first game. While Sora is the only one who uses the Keyblade in the first game, later games reveal more characters who wield Keyblades. In Birth by Sleep, Keyblades can be transformed into hovercrafts called Keyblade Gliders, which can be used to travel from world to world, making Keyblade wielders the only people with the means of transportation between worlds before Gummi Ships are used.

χ-blade
The χ-blade (χブレード) is a special Keyblade introduced in Birth by Sleep that is capable of directly unlocking Kingdom Hearts. It is a double-handed weapon that takes the shape of two "Kingdom Key" Keyblades that that intersect in an "X" shape, with additional features that give it the shape of an actual sword. The χ-blade can be created when two hearts of equal strength—one of pure light and one of pure darkness—clash with each other. With the creation of the χ-blade, the user can summon and open Kingdom Hearts. As shown in Birth by Sleep, Master Xehanort originally tries to create the χ-blade by training Ventus to become a user of darkness and pit him against Master Eraqus' light-wielding students. After this fails, Xehanort instead extracts the darkness from Ventus' heart to create Vanitas, a being of pure darkness, and sends Ventus, whose heart becomes pure light, to train under Eraqus. Late in the game, Ventus and Vanitas fuse into one being and create the χ-blade. However, while Vanitas possesses Ventus' body, completing the χ-blade in the physical realm, he is unable to take control of his heart, leaving their fusion incomplete within Ventus' subconscious. This allows Ventus to fight Vanitas from within his subconscious while his friends Aqua and King Mickey are forced to fight their complete fusion in the physical realm, leading them to destroy the χ-blade.

However, this was not the TRUE way to recreate it. As Master Xehanort explains, after being ressurected in Dream Drop Distance, at the end of the Keyblade War, the χ-blade was shattered into seven lights and thirteen darknesses; the lights became the Princesses of Heart. He merely used Ventus and Vanitas to create the χ-blade out of impatiance. Believing he may actualy need to properly forge the χ-blade, he tricked Maleficent into gathering the princesses as a backup plan. Needing twelve other darknesses, Master Xehanort carried on his plans as Xemnas to gather empty vessels to house fragments of his heart; Braig/Xigbar was the first, and willing, vessel of a fragment. This led to the creation of Organization XIII and their Kingdom Hearts, which would be used to split the fragments of Master Xehanort's heart amongst them. However, many of the members proved traitorous or too weak for the process, and Sora destroyed them all.

However, an unseen part of Master Xehanort's backup plan was the assistance of his time-traveling younger self, Young Xehanort, who traveled through the different timelines and gathered Xemnas, "Ansem", Braig, Isa and six others to serve as members of a new Organization XIII along with the revived Master Xehanort. Because they were unable to induct Riku due to his resistance to darkness, they tried making Sora the final vessel, but failed. Because they lacked a thirteenth vessel, the Organization retreated until they had their final member to clash against the Princesses of Heart. Upon their retreat, Yen Sid deciced to gather seven Keyblade wielders to fight against the new Organization, but only Sora, Riku, Kairi, Lea, Mickey and himself were the only ones left -- they were also short by one.

Kingdom Hearts
The titular "Kingdom Hearts" is the "heart of all worlds" and the source of hearts, being in the shape of heart-shaped moon. It is an object of immense power and a central plot element that drives the conflict within the series, appearing through the gathering of hearts, be they from worlds or people. Though only touched upon in the first game, appearing as a sphere of light beyond a white door which Xehanort's Heartless was intending to open, Kingdom Hearts' role is expanded in Kingdom Hearts II as part of Organization XIII's goal to complete their existences. To that end, they use Roxas and Xion's ability to wield the Keyblade to defeat enough Heartless to form Kingdom Hearts over the World That Never Was, expanding it until Xion's demise and Roxas' departure from the Organization. By Kingdom Hearts II, the Organization uses Sora to fulfill their plans instead. Kingdom Hearts is nearly completed late in the game until Ansem the Wise's sacrifice reduces the amount of hearts it is composed of. The χ-blade is said to co-exist with Kingdom Hearts while the Keyblades are "man-made counterparts" to it, at least according to Master Xehanort's notes.

In Dream Drop Distance, Master Xehanort, who has been revived thanks to the destruction of his Heartless and Nobody, explains "Ansem" was creating a Kingdom Hearts of darkness out of the hearts of destroyed worlds to reorganize the universe's balance of light and dark; Sora stopped him. Xemnas was also creating a Kingdom Hearts, but from the hearts obtained from slain Heartless. However, it was not to regain the lost hearts that they each lost; he was going to use its power to place fragments of Master Xehanort's heart amongst the rest of the Organization as part of his plans for the χ-blade.

The TRUE Kingdom Hearts would only return once the χ-blade is forged, meaning all other Kingdom Hearts are pale imitaions of the real thing. This would mean the Kingdom Hearts that appeared in the Keyblade Graveyard when Master Xehanort stole Terra's body, and where Ventus fell into a coma after destroying Vanitas, was the genuine article.

Worlds
In the Kingdom Hearts universe, travel between worlds is not normally possible. Worlds are protected from extraterrestrial interference by an invisible shell. When the heart of a world is opened, the shell breaks apart, appearing as a meteor shower. Fragments from the wall are called "Gummi blocks" and can be used to make spaceships called "Gummi Ships", which serve as the main mode of travel between the various worlds. Gummi Ships can be shaped into any structure, and the origin of the Gummi Ship material allows for travel to other worlds. Gummi blocks can serve different functions, from navigation to offense and defense. Other methods to travel between worlds are the "corridors of darkness" and the "lanes between"—interdimensional pathways through which frequent travel eventually erodes the user's heart with darkness. These pathways are normally used by Heartless and Nobodies, but have been used by other characters in the series, including Riku and Mickey Mouse.

Those who travel between worlds are advised to limit their interactions with the inhabitants of foreign worlds in order to maintain the world order. For this reason, the main characters change their appearance in certain worlds to avoid standing out. In the worlds based on The Little Mermaid and The Nightmare Before Christmas, Sora, Donald, and Goofy transform into undersea creatures and Halloween monsters, respectively. For The Lion King, they transformed into animals (or, in Donald and Goofy's case, less humanoid forms) because Nomura felt that it would appear odd to have Sora and the others interact in their standard forms, since no humans appear in that film.

Disney worlds
The majority of worlds that appear in the games are based on Disney films. Most of these worlds, such as Wonderland, the Land of Dragons, and Deep Jungle, follow abridged versions of the stories found in their respective films. Agrabah notably covers the first two Aladdin films in Kingdom Hearts and Kingdom Hearts II, while Halloween Town and Atlantica only mirrors its films in the second game, having an unrelated plot in the first game. On the other hand, worlds like Monstro and Neverland focus heavily on the main Kingdom Hearts plot, the latter being reduced to Captain Hook's ship, where Riku reveals to Sora that Kairi has lost her heart. Beauty and the Beast is an interesting case—the Beast appears in Kingdom Hearts to aid Sora when he temporarily loses the Keyblade. After Beast's Castle is restored at the end of that game, the Beast becomes a pawn in the plot of Organization XIII during Kingdom Hearts II.

During the development of Kingdom Hearts II, Nomura had more creative freedom due to advances in technology. Port Royal, Space Paranoids, and Pride Land, in particular, benefited from these advances. In Port Royal and Space Paranoids, the character models were generated from live-action pictures using a new program. Nomura had wanted to include a world based on The Lion King in the first game, but could not since its engine could not process quadrupedal character models properly, a feature which was resolved for Kingdom Hearts II. A sub-world of Disney Castle is Timeless River, meant to be the "past" of Disney Castle, shortly before it was built. The world is portrayed in black and white; Nomura had intended it to be this way from the beginning of development. The world has many throwback effects including intentionally poor sound quality to imitate old cartoons. In this grayscale world, Sora's character model is simplified to the style of early cartoons, while Goofy and Donald Duck revert to their original designs from when they first appeared in Disney cartoons. In Kingdom Hearts 3D: Dream Drop Distance, Country of the Musketeers served as a basis for the movie, Mickey, Donald, Goofy: The Three Musketeers. Notably, it is the first world in the Kingdom Hearts series originating from a direct-to-video feature instead of a film from the Disney animated features canon.

In addition to the Gummi Ship minigame, minigames feature prominently in certain worlds. The 100 Acre Wood in all three games consists entirely in minigames based on classic Winnie the Pooh shorts, with Sora taking on the role of Christopher Robin. Olympus Coliseum features optional fighting tournaments; due to Hades' popularity, the Underworld was added in Kingdom Hearts II, where Hades has opened his own tournament. While Atlantica is a normal world in Kingdom Hearts, albeit with a special "underwater" control scheme, it becomes an interactive rhythm game in Kingdom Hearts II which is completely unrelated to the overall story and serves as mere filler. Finally, Space Paranoids features a Light Cycle mini-game that strongly deviates from the original film. Nomura included this minigame because he knew people associated the Light Cycles with Tron. Kingdom Hearts Birth by Sleep introduced several new Disney-based worlds to the series, such as Castle of Dreams, Enchanted Dominion, Dwarf Woodlands and Deep Space. Kingdom Hearts 3D: Dream Drop Distance introduced more new Disney worlds, such as La Cité des Cloches, Prankster's Paradise, Country of the Musketeers, Symphony of Sorcery, and The Grid.

Original worlds
The worlds created specifically for the series predominantly feature original and Final Fantasy characters and figure more centrally to the overarching plot of the Kingdom Hearts series. The first world of each game serves as a tutorial to introduce new gameplay elements and frame the story. Destiny Islands, the home world of the main characters, Sora, Riku, and Kairi, serves this function at the beginning of the first game and Kingdom Hearts Re:Coded. The next available world serves as a hub world, where the player returns multiple times throughout the game to unfold the main story. Traverse Town, a world cobbled together from the remains of worlds destroyed by the Heartless, fills this role in Kingdom Hearts, but becomes the tutorial world in Kingdom Hearts: Chain of Memories. The penultimate world of each game wraps up many plot threads in preparation for the final world. Hollow Bastion is this world for Kingdom Hearts, but, in Kingdom Hearts II, it is the hub world. Twilight Town is both the tutorial world and the penultimate world in Kingdom Hearts II, containing a secret pathway to the final world of that game. The final world culminates in a battle with the main antagonist of the game. End of the World, made out of the worlds that lost their hearts to the Heartless, and the World That Never Was are the final worlds of Kingdom Hearts and Kingdom Hearts II, respectively. Kingdom Hearts: Birth by Sleep differs slightly, however. In its case, the Land of Departure serves as the tutorial world, hub world and where the plot threads wrap up. The final world in the game is the Keyblade Graveyard, where each of the main characters' final battles take place.

Hollow Bastion plays a central role in the backstory of the series, as the home world of a majority of the Final Fantasy characters who appear in Kingdom Hearts, as well as the original home of Ansem the Wise, the ruler of that world, then called the Radiant Garden, and Kairi, who was sent to the Destiny Islands as part of an experiment conducted by Ansem's apprentice, Xehanort. Ansem studied the darkness in people's hearts with six apprentices, including Xehanort. His apprentices continued this dangerous research without his permission, causing the world to become overrun by darkness. Deserted, the castle was later adopted by Maleficent as a headquarters. Castle Oblivion, another villainous hideout and the main setting of Kingdom Hearts: Chain of Memories, consists of multiple floors which transform into memory-based reconstructions of other worlds, via special cards. Finally, Organization XIII is based in the World That Never Was, a world in the in-between realm that houses Kingdom Hearts. This conception of Kingdom Hearts was designed to appear as the heart-shaped moon from the cover of the first Kingdom Hearts game. When the scenario writer, Kazushige Nojima, created the scenario, he described it as a moon floating in the World That Never Was. Upon reading that, Nomura thought of using the visuals from the first game to create a connection.

Reception
The series' setting has garnered a mixed to positive reception from critics. Following Kingdom Hearts's initial announcement, publications expressed skepticism towards the first game's viability. Andrew Reiner of Game Informer stated that despite the extreme differences between Final Fantasy and Disney properties, they blend well together along with the new content created for the series. A second Game Informer reviewer, Matt Miller, described the concept as a "hard sell", describing the combination of the two properties as "ridiculous". Though in contrast, he stated the franchise's formula is successful. The graphics of the games have received generous praise, with particular focus on their similarity to the source material. IGN stated that the "worlds look very much like their filmed counterparts". Japanese gaming site, Gpara.com also praised the look of the worlds. GameSpot referred to the worlds as "wonderfully rich familiar environments", and GamePro described the worlds as "spot-on with the original movies."

Following the release of the first game, the Disney settings were well received by critics. Allgame's Scott Marriott stated the Disney settings are the most attractive feature of the game and considered some of the world choices a surprise. He praised the level designs, commenting that a good amount of familiar elements from the Disney films were integrated into them. Marriott further stated that though the stages were small, interacting with beloved characters and exploring familiar settings were enjoyable aspects. Maura Sutton of Computer and Video Games attributed the Disney elements as a major factor in creating the game's "astounding worlds". She summarized her review by calling Kingdom Hearts a "delightful mixture of two enchanted worlds". Video game critics of Kingdom Hearts: Chain of Memories expressed disappointment at the limited number of new worlds to explore in the game. 1UP.com's Bryan Intihar lauded Kingdom Hearts II's environment, calling it appealing and stating it was an improvement over the first title's. He described the level designs as "impeccable", citing the presentation of Timeless River stage's atmosphere. Intihar further commented that the expansions and changes to previous worlds made them "feel fresh". In contrast, Reiner described the Disney elements in Kingdom Hearts II as "tacked on".