Keyblade Graveyard

The Keyblade Graveyard is a world which appears in Kingdom Hearts II Final Mix and Kingdom Hearts Birth by Sleep. It was first revealed in Kingdom Hearts II ' s secret ending, "The Gathering". Before its formal introduction as a world, the Keyblade Graveyard is known as "The Badlands" (謎の荒野).

Setting
The Keyblade Graveyard is made up of unending, rocky badlands, scarred by the battles of the Keyblade War. As such, this world has no natural residents, making it the only world with such a quality.

Early on, Terra and Ventus investigate the world at the Badlands (荒野), where they run into Master Xehanort and Vanitas, respectively. Later, the Vanitas Remnant and Lingering Sentiment appear here, where they challenge intruders to battle.

Each of the heroes eventually enter the true battlegrounds of the world at the Seat of War, a small outcropping of rock overlooking the shattered vista below. It leads into the Twister Trench, where Vanitas's raging emotions have manifested as literal storms of Unversed. After this is the Fissure, a small ravine containing a save point and Moogle Shop. The final area, the titular Keyblade Graveyard (キーブレード墓場) is a crossroads, covered in the Keyblades of the wielders who fell during the Keyblade War. During his battle with the heroes, Master Xehanort creates a pillar of rock from the graveyard, and summons a Kingdom Hearts to shine down upon it.

After Master Xehanort steals Terra's body and is reborn as Terra-Xehanort, Terra's soul animates his armor as the Lingering Sentiment, locks them both within the Will's Cage (思念の檻), and forces him into a final battle. Meanwhile, Ventus and Vanitas have reunited into Ventus-Vanitas, and Ventus is forced to fight off Vanitas's control within Ventus's Mind (ヴェントゥスの精神世界). Both of these areas vanish after the battle ends.

Kingdom Hearts Birth by Sleep
The Keyblade Graveyard is shown numerous times throughout the game as a rather enigmatic place for random battles at first. The world first appears when Ventus sees Vanitas floating through space, and follows him to question him on his earlier comment of Terra no longer being Terra. Ven once again visits the Keyblade Graveyard when he discovers that his friend and companion, King Mickey Mouse, has been abducted to the Keyblade Graveyard by Master Xehanort as to lure him into a trap. Later on, Vanitas appears before Ventus on Destiny Islands and reveals that he is the embodiment of the darkness inside Ventus's heart, and was created by Master Xehanort in the Keyblade Graveyard. At the game's climax, through the manipulations of Master Xehanort, Terra, Aqua and Ventus each end up at the Keyblade Graveyard and meet up. Master Xehanort appears alongside Vanitas, and explains to them that this was the place were a great battle took place, the Keyblade War, also revealing his intentions to use the χ-blade to unlock Kingdom Hearts and unleash the forbidden secrets of the Keyblade War upon the worlds. An epic battle ensues, and after Master Xehanort freezes Ventus and drops him off a cliff, and Vanitas knocks Aqua unconscious, Terra uses the darkness in his heart to fight Master Xehanort.

Terra defeats him, but this allows Master Xehanort to take over Terra's body, thus creating Terra-Xehanort. However, Terra's soul finds its way into his discarded armor, creating the Lingering Sentiment. The two fight, eventually ending with the Lingering Sentiment winning by knocking out Xehanort. Meanwhile, Aqua fights Braig to defend a frozen Ventus. After Braig escapes, she is knocked out by Vanitas. Before he can finish her off, Ventus thaws out and fights him. Afterwards, Vanitas shows his true face, identical to Sora's, and forces Ventus to absorb him and both are transported to the Awakening where they have their last battle while Aqua and Mickey are forced to fight Ventus, possessed by Vanitas. Vanitas is defeated in both fights and fades out of existence, and the χ-blade is destroyed, resulting with Ventus losing his completed heart. A huge blast (created by the shattered χ-blade) transports Xehanort to another world and Aqua and Ventus's bodies into the Lanes Between, where they are found and rescued by Mickey. The Lingering Sentiment kneels down, and swears to Aqua and Ven that one day, he will end this conflict.

Kingdom Hearts II Final Mix
In Disney Castle, a portal to the Keyblade Graveyard appears in the Hall of the Cornerstone. Chip and Dale summon Sora, Donald, and Goofy, who enter the portal and find the Lingering Sentiment alone in the Keyblade Graveyard. The Lingering Sentiment first wonders if Sora is Aqua, Ventus, Riku or even Xehanort. Calling out Xehanort's name, the Lingering Sentiment engages Sora in a fierce battle. Sora manages to defeat the Lingering Sentiment, who respectfully acknowledges Sora as a true Keyblade Master and then returns to his normal position. If Sora comes back to challenge him again, the Lingering Sentiment agrees to fight, but states to Sora that he has nothing left to give him save for his hatred for Xehanort.

Trivia

 * The capital letters in the logo for the Keyblade Graveyard slightly resemble real Keyblades. The "K" bears resemblance to the teeth of the Earthshaker, the "E" resembles the teeth of the Wayward Wind, the "G" bears similarity to the guard of the Rainfell, and the final "D" resembles the guard of the Kingdom Key complete with the Keychain, albeit featuring Sora's Crown Pendant rather than the Hidden Mickey symbol.
 * The "teeth" of Oblivion, Oathkeeper, Sleeping Lion, Follow the Wind, Circle of Life, and Fenrir, as well as the Keychain of Master Xehanort's Keyblade, can been seen coming out of the bottom of the World icon.