Light

Light is a force parallel to Darkness, a strong element used in Synthesis items, and may also be used as an attack in the Kingdom Hearts universe. Although often associated with the forces of good, light is not entirely benevolent; for example, Xemnas uses Roxas's power over light against Sora and Riku in his last stand. The Realm of Light is also one of the three known realms in the Kingdom Hearts universe, along with the Realm Between, and the Realm of Darkness.

Special uses of light
Light can also be manipulated into attacks by some beings within the Kingdom Hearts universe with a strong affinity for it, most notably being Sora and his Nobody, Roxas. Similar to members of Organization XIII's usage of their respective elements, these two are able to physically call and wield the element of light. Roxas's light powers, however, are significantly more advanced than Sora's; he is capable of creating spears and force fields out of light. Sora only seems to be capable of using it to augment a select few of his combo finishers, such as Explosion. However, he also can call to his power of light in his Final Form, during which he can use fighting techniques similar to Roxas's.

Ventus also shows to have an affinity for light-based attacks. He can use several light-based commands like Salvation and Faith, and his ultimate Finish Command, Stratosphere, combines both light and wind into a devastating attack. Aqua also uses light in the four variations of her Deck Command Magic Hour, in where she sends orbs of light spiraling upwards.

Also, during the Final Episode of Kingdom Hearts Birth by Sleep, Ventus's sleeping form is able to summon his Keyblade and open the Door to Light, leading himself and Aqua back to their home of Land of Departure.

Sora's Keyblade, Kingdom Key, is a light-aligned Keyblade. Other notable light-aligned Keyblades are Destiny's Embrace and Way to the Dawn, used by Kairi and Riku, respectively.

On multiple occasions throughout the Kingdom Hearts series, characters have been able to wield light in unique manners not similar to those above. Most notable are the Princesses of Heart, who are able to use their inner light to help those in need. For example, after Sora sacrificed himself and became a Heartless in Kingdom Hearts, Kairi used the light in her heart to turn Sora to back to his original form.

In Kingdom Hearts II, Sora is able to open the "Door to Light" in the Realm of Darkness, at the Dark Meridian. By using the light in his own heart, Sora was able to return himself and Riku to Destiny Islands.

Although she is not a Keyblade wielder or Princess of Heart, Queen Minnie has control over light; when she assists Sora during the Heartless invasion of Disney Castle, they can perform a Reaction Command in which a beam of light falls on her, and releases a shockwave of light; she also occasionally casts "Pearl".