Keyblade Graveyard

The Keyblade Graveyard (キーブレード墓場) is a world which appears in Kingdom Hearts Birth by Sleep. It was first revealed in Kingdom Hearts II ' s secret ending, "The Gathering". In Kingdom Hearts II Final Mix, the Lingering Sentiment can be fought here after a series of side-quests.

Several scans from Kingdom Hearts Birth by Sleep show scenes from this area, including one of Terra confronting Master Xehanort and another of King Mickey protecting Ventus.

Setting
All that has been seen in this world is a deserted sand area. This could be because Keyblade Graveyard only consists of sand and nothing else. The area looks faintly like "The Great Maw" in the Radiant Garden. Some of the scenery appears to have battle scars left from the Keyblade War.

Somewhere on this world is a field covered in the Keyblades of the Keyblade Masters who fell during the Keyblade War. The open spaces in the Keyblades creates a crossroads.

Kingdom Hearts Birth by Sleep
Terra goes to the Keyblade Graveyard and meets up with with Aqua and Ven. 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 X-Blade to unlock Kingdom Hearts and unleash the secrets of the Keyblade War upon the worlds. An epic battle ensues, and after Master Xehanort freezes Ven and drops him off a cliff, and Vanitas knocks Aqua unconsious, Terra uses the darkness in his heart to fight Master Xehanort.
 * Terra's Story

Terra defeats him, but this allows Master Xehanort to take over Terra's body, thus creating Xehanort. However, Terra's soul finds its way into his discrded armor, creating the Lingering Sentiment. The two fight, eventually ending with Terra winning. He knocks Xehanort unconsious, and a huge blast (created by the shattered X-Blade) teleports Xehanort to another world. Terra kneels down, and swears to Aqua and Ven that one day, he will end this conflict.

Aqua meets up with Terra and Ventus in the Keyblade Graveyard, and participates in the battle against Master Xehanort and Vanitas. Aiding a frozen Ventus, she is interrupted by Braig, who wishes to stall her long enough that she is prevented from helping Terra as he fights Master Xehanort. Braig is defeated, fleeing. As Aqua heads back to Ventus's side, she is attacked by Vanitas from above.
 * Aqua's Story

Eventually rescued by King Mickey, Aqua awoke desperately calling out for Ventus. Seeing the boy thawed out and standing in a far corner, she ran to his side and attempted to converse with him. Ventus didn't respond, striking out at her with the completed X-Blade. King Mickey comes to her aid, siding with her as Ventus becomes possessed by Vanitas and battles her. Under Vanitas's influence, Ventus battles Aqua. When Ventus falls, Aqua does all in her power to destroy the X-Blade. Ventus meets up with Terra and Aqua at the Keyblade Graveyard, helping them to battle Master Xehanort and Vanitas. Frozen and dropped from a cliff by Xehanort, Aqua came to his aid before being forced to battle Braig. After Vanitas ambushed her, Aqua's great anger towards the enigma allowed him to stand and face him.
 * Ventus's Story

Vanitas then stated his body was fading, which would allow him to merge with Ventus. He summoned several Unversed to hold Ventus down, stating that the creatures were the negative emotions created when he and Ventus were separated. He then explained that by spreading them throughout the worlds, he hoped he'd lead Ventus and his friends on a little journey, and everything went according to plan, Vanitas viewing the trio's increased strength as a bonus. He then proceeded to fuse with Ventus, transporting him to the Awakening.

Vanitas appeared before Ventus, stating their fusion had been incomplete, hence only an incomplete version of the X-Blade had been created. When Ventus challenged him, Vanitas told him that his destruction would also destroy Ventus's heart, as he was a part of it. Ventus then exclaimed he didn't care, and that he had friends to protect. He then had his final battle with Vanitas, both he and the X-Blade fading out of existence along with him.

Trivia

 * The capital letters in the logo for the Keyblade Graveyard slightly resemble real Keyblades. The "K" bears resemblance to the teeth of the Earth Shaker, the "E" resembles the teeth of the Fresh Breeze, the "G" bears similarity to the guard of the Rain Fall, and the final "D" resembles the guard of the Kingdom Key complete with the keychain, albeit featuring Sora's Crown Pendant rather than the regular chain.