Keyblade of Chaos

The Keyblade of Chaos, alternatively known as the χ-blade, is a legendary weapon that Dr. Koopa wields throughout the Freedom Fighters NEO series and it's semi-canon spin-off. It is a direct upgrade to Enerjak's Sword of Chaos and has the power to unlock Kingdom Hearts. It is also the inspiration for all Keyblades.

Background
The counterpart of the mighty Kingdom Hearts, the χ-blade exists as its protector and equal counterpart. From studying the χ-blade, the Master of Masters discovered the means of materializing Keyblades, weapons imperfectly modeled after the χ-blade, from the hearts of those worthy enough to wield one.

Due to the Keyblade War, the χ-blade was shattered into twenty pieces: seven of light, and thirteen of darkness, and as a result Kingdom Hearts itself was swallowed into darkness. With the conclusion of the war, people came to believe that the Keyblade wielders participating in the war fought for control of the χ-blade and Kingdom Hearts, while in actuality the conflict was caused by the Foretellers' mistrust of each other, and seeing the destruction brought upon, those who would become masters of their own told the tales to their students but discouraged them from attempting to start another war.

Researching the Keyblade War, a Keyblade Master named Master Xehanort learned of the χ-blade and intended to recreate it to begin a new Keyblade War and use Kingdom Hearts to recreate the worlds with pure light and lead them, seeing how both light and darkness were used amorally. Within his reports, Xehanort theorized that the χ-blade could be created when a heart of pure light intersects with an equal yet opposing heart of pure darkness. Although Xehanort anticipated he could potentially fail in creating the χ-blade, which he had a backup plan for, at the same time he decided to take the easily available option at the moment to fulfill his goals. As a result by pure chance, Xehanort used Ventus as a tool to create the χ-blade as he made his heart into one of pure light and used the extracted darkness to create Vanitas.

Creation
However, while creating Vanitas, Xehanort's plan was doomed to fail, not because of Ven's heart being damaged, or because of Vanitas being a being of pure darkness, and therefore he might grow out of control, but because the χ-blade was already forged at the time. In the Forgotten War, which took place in the Prime Zone right after the Keyblade War, Enerjak got one of the pieces of pure darkness and used it to create the Sword of Chaos. Centuries later, the sword was found by Dr. Eggman and stolen by Bowser Jr. When Bowser Jr. transformed into Dr. Koopa and turned against X and Zero, he felt as if the Sword of Chaos is no match for the two or for Metallix, so he decided to upgrade it by extracting soul essence via interdimensional travel. He extracted soul essence from 7 beings of light ( Iris, Sally, Alia, Bunnie, Zooey and Julie-Su, the latter being an ironic case, since she's a Dark Legionarrie) and 12 beings of darkness (Robotnik, Naugus, Mammoth Mogul, Colonel, Sigma, General, Copy X, Zero, Mario, Serges, Violen and Agile), and when he inserted the soul essence in the Sword of Chaos, the χ-blade was forged. Dr. Koopa, however, didn't know about the χ-blade, or about Keyblades in general, so he decided to call it "The Keyblade of Chaos", because it looked like two crossed keys. However, he never used it against X, Zero or Metallix, because of Zero turning into Omega and the Mother Elf "possessing" Iris (in truth, regaining it's body, since the Mother Elf was actually Iris' heart, recreated from Zero's memories of Iris).

Usage
As the pronounciation of "χ-blade" (it's pronounces "chi-blade", and "chi" sounds similar to "key") implies, the Keyblade of Chaos is mostly utilized as a sword. Unlike most Keyblades, who have no visible cutting edge, the Keyblade of Chaos, being a perfect reconstruction of the χ-blade, has one. Like all Keyblades, the Keyblade of Chaos is effective against Heartless, Nobodies, Unversed and Dream Eaters. Although Heartless use Keyblades as beacons, they seemingly know that not even them are a match for the χ-blade if it's wielder has a strong heart, as well as numerous hears of light to support it.

The main power of the Keyblade, however, is the ability to seal or open the barriers between worlds, as well as to "lock" a world's Keyhole, preventing the Heartless from attacking that world's heart. As an offset of this ability, the Keyblade can also be used to lock or unlock any lock, allowing the user to access any sealed interior, whether it be a locked room, gate, or treasure chest. The Keyblade opens and shuts locks by emitting a bright, thin beam of light. The Keyblade can also unlock hearts, as seen when Terra-Xehanort's Dark Guardian is revealed to be Terra's heart. The χ-blade, however, has an unique power among the Keyblades: the power to unlock Kingdom Hearts. When unlocking Kingdom Hearts, the χ-blade uses hearts depending on what hearts the χ-blade's users wants to use. For example, when Dr. Koopa, who wanted to protect the Freedom Fighters and Jumba's experiments from Sonic.EXE, accidentally unlocked Kingdom Hearts, he used the hearts of both the Freedom Fighters and Jumba's experiments.

Keyblade wielders can transform their Keyblades into other objects, vehicles, and weapons though it is hinted that Keyblade wielders can only do this after a certain amount of training.

According to Metallix, the χ-blade has the power to overwrite reality.