Keyblade War

Unreleased The Keyblade War (キーブレード戦争) was a mysterious conflict in which many Keyblade wielders fought, featured in Kingdom Hearts Birth by Sleep. The conflict aroused when Keyblade wielders of Light and Darkness clashed with each other in order to create the X-Keyblade. The attempts failed and in the end, their Keyblades were all that remained.

In the TGS 09 trailer, Master Xehanort reveals that the numerous Keyblades in The Gathering Place are indeed the remains of the Keyblade War and the reason for the fight is between Light and Darkness. This indicated that the War indeed predates the events of Kingdom Hearts Birth by Sleep. In an even more recent trailer, Master Eraqus and Master Xehanort are shown to discuss the Keyblade War.