Seven Guardians of Light

The seven guardians of light (7光の守護者), is a group nominally consisting of seven Keyblade wielders that is first referenced in Kingdom Hearts 3D: Dream Drop Distance.

Kingdom Hearts 3D: Dream Drop Distance
Following their sealing of the seven Sleeping Keyholes, Sora and Riku both end up in The World That Never Was. While the former is put into a deep slumber by Xemnas, Xigbar, and Young Xehanort, Riku escapes from within Sora's dreams and arrives in the true world. Reaching the castle and meeting up with King Mickey, Riku faces Young Xehanort before the other members of the real Organization XIII appear and taunt the heroes. Master Xehanort then reveals his plans to them; while he had originally attempted to create the χ-blade and summon Kingdom Hearts using Ventus and Vanitas, this was not the proper method. Instead, a clash between thirteen hearts of darkness and seven hearts of light would create the χ-blade and allow Xehanort to more properly accomplish his goals. He then states that, should the heroes want to protect the seven Princesses of Heart, they would need to gather seven guardians of light to defend the princesses and face the darkness.

Mickey hypothesizes that the guardians could include himself, Sora, Riku, and his three lost friends (Terra, Aqua, and Ventus), but cannot think of a seventh. Xehanort then contradicts this count, claiming that Sora and Terra, who he refers to as "another on your list", belong to the Organization. Just as Xehanort prepares to send a piece of his heart into Sora to create the thirteenth vessel, Lea arrives to help the heroes escape, later joined by Donald and Goofy. Having been thwarted from claiming Sora, Xehanort tasks both groups with filling in their numbers before they meet again as destined.

Later, after Riku rescues Sora from the Armored Ventus Nightmare, Lea reveals that he had been training to use a Keyblade, and surprisingly manages to summon his Keyblade, Flame Liberator, as he speaks. Yen Sid then tells Riku to bring Kairi to him, where he declares her to be another guardian of light.

Kingdom Hearts III
Yen Sid sends both Lea and Kairi to Merlin, where the two were trained in order to join the guardians of light and be able to battle against the real Organization XIII in equal footing. Meanwhile, both Riku and Mickey seeks out a way to rescue Aqua from the Realm of Darkness, while Sora travels to other worlds in order to regain his lost strength. In time, he joins Riku and Mickey as the former battles against Anti-Aqua, and succeeds in expunging the dark influence from Aqua and rescuing her from the dark realm.

Members

 * Sora: A boy from Destiny Islands which has the ability to wield the Keyblade. With the help of friends he's save the world several times.
 * Riku: Sora's best friend and a Keyblade Master.
 * Mickey: The king of Disney Castle and a Keyblade Master.
 * Lea: Human form of Axel and one of the new Keyblade wielders under Master Yen Sid and Merlin.
 * Kairi: A Princess of Heart and one of the new Keyblade wielders under Master Yen Sid and Merlin.
 * Aqua: One of Eraqus's students and a Keyblade Master who was brought back from the Realm of Darkness by Sora, Riku, and Mickey.
 * Ventus: One of Eraqus's students who was brought back from his sleep by Sora's Power of Waking.
 * Terra: One of Eraqus's students. Initially a member of the real Organization XIII as Terra-Xehanort's vessel, he manages to regain control of his body with the help of Sora. After Lea's Flame Liberator is broken by Xemnas, Terra takes his spot as a guardian of light during the final battle.
 * Roxas: Sora's Nobody and a member of the first Organization XIII. With the help of Ansem the Wise, Ienzo, Vexen, Saïx, and Demyx, Roxas manages to obtain a vessel for his heart and becomes a guardian of light during the final battle, fighting in Lea's places after he's injured by Xemnas.
 * Xion: A member of the original Organization XIII, a replica crafted from Sora's memories of Kairi by Vexen. She was a member of the real Organization XIII before deserting it and joining the Guardians of Light, taking Kairi's place in battling Saïx when Xemnas kidnaps the Princess of Heart.
 * Donald Duck: Mickey's court magician of Disney Castle. Even without a Keyblade, Yen Sid considers him a Guardian of Light. He helps Sora and Goofy defeat Xehanort.
 * Goofy: Mickey's captain of the guards at Disney Castle. Even without a Keyblade, Yen Sid considers him a Guardian of Light. He helps Sora and Donald defeat Xehanort.
 * Riku Replica: A replica of Riku created by Vexen who was seemingly destroyed, but was really residing in Riku's Heart. He helped Riku defeat Dark Riku by taking away his body, leaving an empty vessel to be used for Naminé.
 * Naminé: Kairi's Nobody and a former witch. Despite not participating in the war herself, she sends Sora, Riku, Kairi, Lea, Aqua, Ventus, Mickey, Donald, and Goofy back before their deaths at the hands of Terra-Xehanort and alerts Terra's Lingering Will to prevent the possessed vessel from hurting them again, allowing them to continue the fight. After Riku Replica separates Dark Riku from his vessel, said vessel is used for Naminé after the war.
 * Yen Sid: A powerful wizard as well as Mickey's teacher and a retired Keyblade Master. When Sora, Riku, Kairi, Lea, Aqua, Ventus, Mickey, Donald, and Goofy are trapped by hundred of Heartless, Nobodies, and Unversed once again, Yen Sid interferes and creates a path for the Keyblade wielders to go forward while Donald and Goofy stay behind to help him.