Just a little theory:
So MX is visibly very old. After the Exam, MX encourages Terra to open to the darkness. Do you think MX is trying to posses a younger body? We saw in KH1 that a heart of darkness is easy to posses.
So maybe after the big battle between Terra, Aqua, Ven, Vanitas, and MX, Terra gets so upset over Ven's possible death that he accepts the dark. Xehanort posses him, and goes to kill Eraqus. Meanwhile Aqua has taken Ventus to Castle Oblivion, in some attempt to save him. He is left in the Room of Awakening.
Vanitas and "Terranort" go to Radiant Garden to capture Kairi. Aqua arrives to stop them, and in the battle she causes "Terranort" to kill Vanitas. "Terranort" then mortally wounds Aqua, and the Terra side of Terranort sees this and takes over. Mickey helps Aqua and they leave to evacuate Kairi, leaving Terranort in a mental battle, on the brink of insanity. A while afterwards, Ansem finds a man with white hair and no memory.
A few days later, there is a meteor shower over Destiny Island. Young Sora and Riku find a girl on the shore, as Aqua watches from the Paopu tree.
So MX is visibly very old. After the Exam, MX encourages Terra to open to the darkness. Do you think MX is trying to posses a younger body? We saw in KH1 that a heart of darkness is easy to posses.
So maybe after the big battle between Terra, Aqua, Ven, Vanitas, and MX, Terra gets so upset over Ven's possible death that he accepts the dark. Xehanort posses him, and goes to kill Eraqus. Meanwhile Aqua has taken Ventus to Castle Oblivion, in some attempt to save him. He is left in the Room of Awakening.
Vanitas and "Terranort" go to Radiant Garden to capture Kairi. Aqua arrives to stop them, and in the battle she causes "Terranort" to kill Vanitas. "Terranort" then mortally wounds Aqua, and the Terra side of Terranort sees this and takes over. Mickey helps Aqua and they leave to evacuate Kairi, leaving Terranort in a mental battle, on the brink of insanity. A while afterwards, Ansem finds a man with white hair and no memory.
A few days later, there is a meteor shower over Destiny Island. Young Sora and Riku find a girl on the shore, as Aqua watches from the Paopu tree.