Gate

In Kingdom Hearts, the Keyholes were sealed, leaving no way to travel between each world. About a year later, the Heartless found another method of traveling between worlds, creating their own Gates. A good portion of the Gates are revealed in Kingdom Hearts II.

The Gates are opened when a specific item or object, different for each world, is surrounded in light and then a huge gust of wind blows. The item in question reveals the Keyhole to a route and then Sora spins his Keyblade and unseals the Gate. Sora, Donald, and Goofy continue on their adventures thereafter with the new route opened.

It is likely that worlds within worlds do not have Gates, because the outer world's Gate also serves as their own. This appears to be true for Space Paranoids, 100 Acre Wood, and Timeless River.

List of Gates

 * Twilight Town: The blue orb from the Struggle Trophy.
 * Hollow Bastion: The Hollow Bastion Restoration Committee honorary membership card given to Sora by Leon.
 * The Land of Dragons: Shan-Yu's sword.
 * Beast's Castle: Beast's Rose.
 * Olympus Coliseum: The Olympus Stone.
 * Disney Castle: The Cornerstone of Light after you return from the Timeless River.
 * Atlantica: A bubble.
 * Port Royal: Jack Sparrow's Compass.
 * Agrabah: A ruby from the Cave of Wonders.
 * Halloween Town: Jack Skellington's Santa Claus costume.
 * Pride Lands: Mufasa's Ghost.
 * Realm of Darkness: The Sea-salt ice cream given by Riku.

Trivia

 * In Kingdom Hearts II, when Sora unlocks a world's gate, a symbol shaped like Sora's crown pendant appears beneath him.

Verrou Céleste