Light

Light is a force parallel to Darkness, an element for Synthesis items, and is also used in the form of attacks in the Kingdom Hearts universe. Often associated with good simply because of the classic views of things, this is not always true as seen with Axel, Riku and a handful of other characters.

Light is also one of the four known realms of the Kingdom Hearts universe, they are as follows: Realm of Light, Realm of In Between, Realm of Darkness and the Realm of Nothingness.

Weapons and Special Uses of Light
Sora's Keyblade, the Kingdom Key, is a Light aligned Keyblade. Other notable Light Keyblades are Oathkeeper, Kairi's Keyblade and Way to the Dawn. The alignments of most player collectable Keyblades are still unknown at this point and purely speculation among the community.

Light can also be manipulated into attacks by some beings within the Kingdom Hearts universe, most notably being Sora and his Nobody Roxas. Similar to members of Organization XIII these two are able to physically call and wield the element of Light to their aid, although Sora is mostly unable to do so until much later in Kingdom Hearts II. Light is also an element found within magic as is seen with the spell Reflect.

On multiple occassions throughout the Kingdom Hearts series characters have been able to wield Light in unique manners not similar to those above. The most memorable of these would be the Princesses of Heart who are able to use their inner light to help those in need. Additionally Kairi is able to use the Light in her Heart during the confusion at Hollow Bastion following Sora's sacrifice to return his heart to him during the events of Kingdom Hearts. In the sequel, Sora is able to open the "Door to Light" in the Realm of Darkness using his Heart's Light to return himself, Riku, Donald, and Goofy to the Realm of Light on Destiny Islands. It should also be noted that Queen Minnie has limited control over Light as is seen with her "Limit"/Reaction Command with Sora, Faith.