you are in the keyblade graveyard, you are with Aqua, Terra and Ventus, and they are going to face Xehanort and Vanitas

Xehanort: "In ancient times, people believed that light was a gift, from a never-before-seen land called Kingdom Hearts. But Kingdom Hearts was safeguarded by its counterpart, the χ-Blade. In a war they competed for that precious light, thus beginning the "Keyblade War". The violent crash broke the χ-Blade into twenty pieces, seven of light and thirteen of darkness. And only the real Kingdom Hearts was swallowed by darkness, never rising to the surface again... Until now... Thanks to the pure light of Ventus, and the absolute darkness of Vanitas, The χ-blade will be forged again, releasing Kingdom hearts!"

upon hearing that, Terra, Aqua and Ventus hit their shoulders, magically (?) putting on their keyblade armor