Role in the game
Not only is the Land of Departure the place where Keyblade apprentices take their Master Qualification Exam, but it is also where friends Terra, Ventus, and Aqua first make note of the Paopu Fruit's legacy. Knowing they would be split up during a great adventure, Aqua distributes tokens to her fellow Keyblade apprentices, stating that through them they will always be together. However, only Aqua and Terra take their exam here, as Ventus will not be ready.
At some point during the game, the Land of Departure becomes shrouded in darkness, because of this, most of the castle is destroyed. After Ventus loses his heart and falls into a comatose state, Aqua returns to the destroyed castle with Ventus, carrying him on her back. She places Ven in the middle throne and, using Eraqus's Keyblade, activates the device which transforms the Land of Departure into Castle Oblivion. She then leaves Ven in a chamber, known now as the Chamber of Waking, which strongly mirrors a chamber in Hollow Bastion, the Chamber of Repose.