The Keyblades (キーブレード Kīburēdo ) are mysterious weapons that are heavily featured in the Kingdom Hearts series. Wielded by the main character, Sora, as well as a number of other important characters, the Keyblade is a main part of the battle between Darkness and Light.
According to an interview with Tetsuya Nomura, the original weapon shown during development was actually a chainsaw-like weapon. This was eventually scrapped in favor of the Keyblade.
Before Kingdom Hearts Birth by Sleep
Long before the events of the Xehanort Saga, in the "age of fairy tales" when the world was whole, Kingdom Hearts gave Light to the world. However, it remained out of mankind's reach, as the way to it could only be unlocked by the χ-blade which coexisted with Kingdom Hearts and symbolized the perfect crossing of light and darkness. Eventually, darkness sneaked into the hearts of mankind and caused them to become jealous and greedy; they forged the first Keyblades in the image of the χ-blade in order to unlock Kingdom Hearts and take the Light for themselves. In response, defenders of the light forged their own Keyblades and attempted to stop the servants of darkness. This battle erupted into a grand Keyblade War which embroiled even those who did not desire Kingdom Hearts, and took the lives of thousands, as well as extinguishing light from the world and trapping Kingdom Hearts in the deepest darkness. The final site of the Keyblade War became the barren Keyblade Graveyard, littered with ancient Keyblades.
However, because light remained in the hearts of children, it was able to draw the fragments of the world back together into separate worlds. The remaining Keyblade wielders decided to use the Keyblade in order to protect what was left of the Realm of Light. They primarily settled in worlds within the Realm Between, such as the Land of Departure, where the Realm of Light bordered the Realm of Darkness. Memories of the Keyblade War survived in various legends, which disputed whether the Keyblade was used to save the world or to wreak chaos and destruction upon it.
Kingdom Hearts Birth by Sleep
Ten years before Sora's first journey, there were eight known Keyblade wielders: Ventus, Aqua, Terra, Master Eraqus, Master Xehanort, Vanitas, Master Yen Sid, and Mickey Mouse. When they confront him at the Keyblade Graveyard, Master Xehanort explains to Terra, Aqua, and Ventus that the Keyblades at Keyblade Graveyard are the remains of the Keyblade Wielders after the Keyblade War between the forces of Light and Darkness.
At one point, Terra performs the Keyblade Inheritance Ceremony with Riku, making the child into a potential Keyblade wielder, and Aqua accidentally does the same with Kairi. She meant to perform it purposefully with Sora before deciding against it, but instead Ventus is the one who gives Sora the ability, when the two boys join hearts after the destruction of the χ-blade; however, neither of them realize it at the time.
When the worlds first started to disappear, King Mickey realized that Kingdom Hearts was going to be opened, and went to the Realm of Darkness to find its Keyblade, with which he could seal the door. However, he would also need someone to use a Keyblade from the Realm of Light in concert with him, so he left a letter for Donald Duck and Goofy, asking them to find the chosen wielder of that Keyblade and assist him in saving the worlds.
When the Heartless invade Destiny Islands, Sora rushes to the small island to save his friends, but finds that Kairi and Riku have already been swallowed by darkness. It is at this point that the Keyblade which Terra had promised Riku finally appears on the island, but because Riku has already given himself to darkness, the Keyblade falls to Sora's ownership. When Sora first arrives at the Traverse Town, he meets Leon which later gives him shelter and some insight about the Keyblade and Heartless. Yuffie and Leon have to get Sora off the Keyblade since it's the only way to "conceal his heart (Sora's)," this is due to the Heartless fear of the Keyblade and they will stop at nothing to eliminate the wielder of the weapon.
On Atlantica, King Triton is enraged when he finds out that Sora is the key bearer and he tells him that as a key bearer, one must not meddle in the affairs of another world and that Sora had violated the principle. He also thinks that the Keyblade and its wielder can only shatter peace and bring ruin.
Sora uses this Keyblade to seal the Keyholes of the worlds he visits, but when he arrives at Hollow Bastion, Riku reveals that the Keyblade was intended for him, and takes it back as Sora's heart falters. However, Sora soon confronts Riku, and the strength of his heart proves greater than Riku's, allowing him to steal the Keyblade back.
Confused and angry, Riku runs off and is found by Ansem, who convinces Riku to give Ansem his body in exchange for more power. This new "Dark Riku" summons the Keyblade of People's Hearts from the Princesses of Heart, in order to unlock the Final Keyhole, but it remains incomplete due to it lacking Kairi's heart. When Sora tracks down Dark Riku and confronts him, Dark Riku reveals that Kairi's heart is in fact within Sora, and attacks Sora in order to steal it. Sora defeats Dark Riku, but in order to restore Kairi's heart and fully seal the Final Keyhole, he uses the Dark Riku's Keyblade on himself, completing the keyhole and restoring all of the Princess's hearts at the cost of his body and soul.
Later on, after Sora, Donald, and Goofy defeat Ansem and attempt to close the door to Kingdom Hearts, King Mickey finally reappears with the Kingdom Key D, the Keyblade of the Realm of Darkness that he had gone to search for. With their help, as well as that of the restored Riku, they close the door, saving the worlds from the imminent flood of darkness.
Kingdom Hearts: Chain of Memories
Since Sora retained his memories and feelings as a Heartless, something only one other person had done, Axel becomes particularly interested in why the Keyblade chose Sora as its wielder. Tired of Xemnas's rule, Marluxia conspires with Larxene to use Naminé's magic to rewrite Sora's memories so they can use his Keyblade's power to overthrow the Organization.
Kingdom Hearts 358/2 Days
As Sora's Nobody, Roxas can use his Keyblade. In addition, Xion is created by Xemnas to ensure there will be a Keyblade wielder loyal to the Organization. Upon Xion's destruction, Roxas awakens the ability to wield two Keyblades, Sora's and Ventus's. The Keyblade was used during this time as part of Xemnas's plans for his Kingdom Hearts.
Kingdom Hearts II
Sora, Riku, Kairi, Roxas, and King Mickey can use the Keyblade. Sora uses the Keyblade to open new paths to new worlds through Gates. While King Mickey comes out occasionally to assist Sora, Riku receives his own Keyblade shortly before reuniting with Sora and Kairi in The World That Never Was.
Kairi's use of the Keyblade is limited to the Heartless surge in the Castle That Never Was.
Kingdom Hearts coded
Data-Sora can use his digital version of the Kingdom Key to fix the World source of Bug Blox and to seal the data Keyholes. His digital Keyblade was destroyed in Episode 5, but gained a new Keyblade in Episode 6. King Mickey explains that this Keyblade is tightly connected to the Power of the Heart, implying that his Keyblade is genuine.
King Mickey also uses his own Keyblade to defeat the Heartless that attack his castle.
Kingdom Hearts 3D: Dream Drop Distance
All Keyblades share the same fundamental features, modeled after a key: a guard with a handle, a hilt, and a head at the end of the shaft that resembles the teeth of a skeleton key. The exception is the Fenrir, which is instead modeled after a pin tumbler lock key.
The original χ-blade's existence was intimately linked with the existence of the true Kingdom Hearts, and so it was destroyed along with Kingdom Hearts in the first Keyblade War; however, Master Xehanort's research uncovered that it can be reforged by fusing a heart of pure light with one of pure darkness. The lesser Keyblade of heart, whose existence opens a path to any existing Kingdom Hearts whether they be pure or incomplete, can instead be forged from the union of seven hearts of pure light.
The method for forging a regular Keyblade is not entirely clear, although several newly-forged Keyblades do appear in the series. Riku's Keyblade, the Way to the Dawn, was able to manifest by using his Soul Eater as an intermediary, while Data-Sora's strength of his heart allowed him to create a true Keyblade after his artificial, digital Keyblade was destroyed by Maleficent.
The Keyblade only lets a chosen wielder hold it, but those with the strength of heart to wield a Keyblade are able to give or take them from others, or take control of them if they have been abandoned. A wielder is able to summon or dispel their Keyblades at will. Those incapable of wielding a Keyblade cannot keep it, even if a wielder hands it to them. Furthermore, Sora and Roxas, who share two Keyblades, are able to use Synch Blade and channel each of their Keyblade's innate abilities at the same time; however, it is unknown if this ability is exclusive to them.
It is also possible for a wielder at the level of a Master to choose someone of a strong enough heart as their successor. This is often done through the Keyblade Inheritance Ceremony, but can also be performed informally when the wielder lets a candidate touch their Keyblade, or if their hearts link together.
The Keyblade's main ability is the power to open or close any lock, whether it be a physical object, or even the heart of a person or world. Their ability to unlock a person's heart makes them particularly effective weapons against Heartless and Nobodies, but also draws these beasts to the wielders. Meanwhile, their power over a world's heart allows a wielder to open or seal the barriers between worlds, or even lock the world's heart to protect it from darkness. Keyblades usually exercise this power by emitting a bright, thin beam of light, but can also work by being directly impaled into a person's chest.
In combat, Keyblades are used in a manner similar to swords. Despite most Keyblade's lack of a cutting edge, or the apparent frailty of their design, Keyblades are able to serve as both excellent blunt weapons, and supernaturally precise cutting tools. Keyblades can be used to channel the powers of light or darkness, and are also natural conduits for magic; even Keyblade wielders without formal training are able to perform magic with power rivaling that of expert mages.
Keyblade wielders are also able to modify the size and shape of their Keyblade. This can be used to merely augment their use as weapons, or even to transform the Keyblade into a vehicle called a "Keyblade Glider", which the wielder may use to traverse the Lanes Between. A Keyblade wielder can also attach a Keychain or Gear to their Keyblade in order to transform it into a set size and shape, as well as to channel the Keychain's innate strengths and abilities. Equipping a Keychain also changes the effect generated when the Keyblade is summoned; this effect is generally based on the Keychain's symbolism.
Prominent Keyblade wielders
The most prominent character in the series to use a Keyblade is Sora, who has used them successfully in the two main games in the series (with one minor incident). His ability to use and possess the Keyblade was a major plot point in the first game. He has used more Keyblades than anyone else in the Kingdom Hearts series; the variations are created through various keychains attached to his original blade, the Kingdom Key.
Sora's Keyblade is a "Keyblade of Worlds' Hearts", and nearly all of his Keychain tokens represent some important item from a world he has saved. Usually, Sora is not actually shown to be given the Keychain from one of his many friends, so it is possible that after saving a world, or completing a major step in that direction, the world itself rewards him with the ability to access its power in the form of a unique Keychain.
Keychains that Sora receives from his friends, or from defeating challengers in the Olympus Coliseum, always use a token that is somehow intimately symbolic of that person. While Sora's Keyblade is not specifically a Keyblade of human hearts, like the explicitly named Keyblade of People's Hearts, it is likely that the connections between his heart and those he meets allow him to sometimes access their power as well. Sora and Roxas's Oathkeeper and Oblivion are said to specifically embody Sora's memories of Kairi and Riku and Roxas's oath to Xion before her death (Oathkeeper) as well as her demise (Oblivion) and so it is extremely likely that for "people-Keyblades" like these, the Keychains act as a physical embodiment of the memories Sora and Roxas have of those that are important to them. Keyblades that represent entire worlds likely function the same manner, being formed from Sora's memories of that world.
The King of Disney Castle, King Mickey's Keyblade is known as "Kingdom Key D". It looks the same as Kingdom Key, but its colors are inverted compared to the Kingdom Key. In Kingdom Hearts coded and Kingdom Hearts Birth By Sleep, he uses the Star Seeker, the Keyblade he used in his days as an apprentice under Yen Sid.
Sora's best friend and rival, he wields the Way to the Dawn Keyblade, though in Kingdom Hearts he briefly took possession of Sora's Kingdom Key. In Kingdom Hearts, he stayed behind with King Mickey in the Realm of Darkness. In Kingdom Hearts: Chain of Memories, he explores the basement of Castle Oblivion and struggles in resisting the darkness in his heart, Ansem, Seeker of Darkness, while in Kingdom Hearts II, he helped Sora defeat Xemnas. In Kingdom Hearts: Chain of Memories and Kingdom Hearts, he used the Soul Eater as his main weapon until it transformed into the Way to the Dawn Keyblade.
Sora's Nobody and the thirteenth member of Organization XIII, Roxas also possesses the ability to wield the Keyblade, an ability which Xemnas uses to his advantage by ordering Roxas to gather countless hearts to complete Kingdom Hearts itself. Upon the absorption by Roxas of his Replica, Xion, Roxas regains the ability to wield the two Keyblades, Oblivion and Oathkeeper, an ability passed onto Sora when Roxas fuses with him. Roxas utilizes Gears, which function more or less exactly the same as Keychains would, and create Keyblades that feature apparent Keychains.
Terra, Aqua, and Ventus
Three Keyblade wielders before Sora, apprentices under Master Eraqus. Sharing a common foe, Master Xehanort, they each suffer horrific fates due to Xehanort's doing at the end of the game: Terra is possessed by Master Xehanort and becomes Terra-Xehanort; Ventus is rendered comatose after his heart is damaged following a victorious confrontation with his dark side, Vanitas; and Aqua is stranded in the Realm of Darkness. All three currently await for Sora to rescue them from their fates.
Master Xehanort is the primary antagonist of the "Xehanort Saga", but makes his appearance through a variety of incarnations, most of which can wield the Keyblade. He himself is a Keyblade Master who plans to restart the Keyblade War; his hybrid form Terra-Xehanort has the same abilities, but is inflicted with amnesia soon after creation and forgets how to use them until shortly before he splits himself into a Heartless, Ansem, and a Nobody, Xemnas. While Ansem is implied to have required Riku's body to wield the Keyblade of People's Hearts, series-creator Tetsuya Nomura has hinted that Xemnas had the ability but intentionally did not exploit it. Master Xehanort's youthful, time-travelling "Young Xehanort" identity can also wield the Keyblade as well as weapons similar to Ethereal Blades, and No Heart, a data simulation of Xehanort in his Keyblade Armor, wields a data simulation of Master Xehanort's Keyblade.