Keyblade

Keyblades are mysterious weapons that share a link with their owners. Keyblades can be used as weapons and as a means of locking and unlocking anything, be it doors, chests, or links to worlds. Some keyblades have been known to even unlock the darkness to peoples hearts. Keyblades have the ability to change in appearance simply by changing the "key chain" at the bottom of the keyblade. Very little else is known about these tools except they choose there own masters and only choose those with strong hearts.

Keyblades

Sora's KIngdom Key (Realm of the Light)

Sora's keyblade is called the Kingdom Key, and in the Kingdom Hearts universe seen as the keyblade. He acquired it when his island was being overrun with heartless. It is described as "a Keyblade from the realm of light." It was originally chose to be wielded by Riku but when he chose to be engulfed by the darkness it weakened his heart and thus, the keyblade chose Sora. The Kingdom Key has the ability to open and close keyholes to worlds and change its appearance through key chains. It is yet clear as to if any other keyblades have these powers. This Keyblade has a strong link to Sora and will often teleport back to him if ever taken (ex: Leon, Roxas, Jack Sparrow). Roxas being Sora's nobody has the ability to use this keyblade as well. Roxas and Sora have both used a keyblade at the same time so it would seem that it isn't a simple matter of one keyblade, but rather one type per user. Xion used a keyblade like this one that later was revealed to be a sham. In one odd acurance, Riku was able to summon Sora's Keyblade from him but it later returned back to Sora.

Way to the Dawn

Riku's Keyblade is the Way to the Dawn. It seems to be an evolved from of the Soul Eater sword, which was formed from the darkness in his heart. The name and design of this keyblade refers to how Riku "travels between the light and the dark." the design combines both angel and devil wings to further show this. It also appears to have multiple crosses lodged in the Keychain, and it bears a heart symbol that closely resembles the Heartless emblem.

Kairi's Destiny's Embrace

 
Next to nothing is known about Kairi's Keyblade. It has a flowing Floral design and the paopu fruit key chain to represent Destiny Island.  It is given to her by Riku near the end of Kingdom Hearts 2. Since Kairi is able to wield a Keyblade is likely because of how strong her heart was as shown in the first game. Tetsuya Nomura has said the scene in which Riku gives her a Keyblade hints at something.

King Mickey's Kingdom Key (Realm of the Darkness)

King Mickey's Kingdom Key is a Keyblade from the Realm of the Darkness and it is the counterpart to Sora's Realm of the Light Kingdom Key. In is identical to Sora's Keyblade except that the colors are inverted and Mickey's is slightly smaller to match his size. When used in tandem with the Realm of the Light Keyblade, Sora and Mickey are able to seal the Door to the Darkness. It is safe to assume that this keyblades abilities are identical to Sora's.

Terra's Ends of the Earth

Not much is known is known about this keyblade except that it is owned by one of the keyblade warriors, Terra. Unlike other keyblades, this one does not have a key chain and is summoned in a digital fashion like Roxas summoned his in the fake Twilight Town. Also, Terra's keyblade can transform into different weapons (as seen in the boss battle against him in Kingdom Hearst II: Final MIx ). So far it is known to take the shape of a whip, a cannon, a fast spinning
cog-like weapon, and a vehicle of some sort. It is most likely that in Terra's game, Birth by Sleep, you will be able to unlock other keyblade forms.

Aqua's Stormfall

 
Nothing is known about this keyblade because of Aqua's preference for magic in the Birth by Sleep video. What is known is, like Terra, her keyblade has no chain and in a scene in Kingdom Hearts: Final Mix , Aqua's Keyblade and Armor are seen on the floor of Xemnas' Room of Sleep.

Ven's Wayward Wind 

Ven's Keyblade is uniquely designed to be held in reverse. Like the other two, it lacks a keychain.