Before I start, I'm going to have to ask you to suspend your disbelief. Now I have yet to see anyone comment on things such as this, so I'm hoping I'm not rehashing old theories here.
Disclaimer: Yes, I am fully aware of the insane lack of evidence for any of this, hence why it is considered wild theorizing. :3
Kingdom Hearts. We don't know exactly what it does, but I believe Master Xehanort knows exactly the extent of its power and intends to use it in Birth By Sleep as a means to save himself from his own mortality in a way. He's clearly old, possibly on his last legs, and he's looking for a way out.
Here's where it gets nuts and will probably elicit many flames. I think the third chair in the room where Erauqs announces the Master Qualification Exam belonged to a now-deceased Master, who was killed by either Master Xehanort or his apprentice, Vanitas. The Exam is designed to find a fitting replacement for their deceased comrade, and Terra and Aqua are the two closest and best prepared Keyblade Wielders to undertake the test, so it will be one of them. I don't believe Master Xehanort cares much about who gets the seat, just that the test has begun.
He was trying to get Terra away from his Master so that he (Master Xehanort) could convince Terra to fall to Darkness.
Why?
Master Xehanort was preparing Terra to be his new Vessel once Kingdom Hearts is complete.
I theorize that Master Xehanort's Soul orchestrated or incited the Keyblade War however long before Birth By Sleep it took place in order to generate a Kingdom Hearts for a similar purpose earlier, which placed him in the body in which he resides in Birth By Sleep. Perhaps the results of this body jumping caused the body to age much more rapidly than it should have, thus causing him to become much too old much too quickly. This also may have been the result of the original owner of the body struggling against the parasitic Soul of Xehanort.
I believe Master Xehanort was initially planning to utilize Vanitas as his Vessel, but Xehanort ran short on time, as his body would soon be too old and frail to support him any longer and Vanitas was still not strong enough to support his Soul, so he turned to Terra.
So, then, at the end of Birth By Sleep, Master Xehanort succeeds in his master plan, taking Terra's body for his own, though Terra's Heart and Soul stay with it, something Xehanort did not anticipate. This melding of Xehanort's Heart and Soul with Terra's complete being resulted in the both of their memories being delinked, with only the one overlapping memory, the name "Xehanort," remaining.
Perhaps, too, Xehanort indeed remembered much, much more than simply his name, though feigned ignorance of these Memories. He opened the Door to Radiant Garden's Heart on purpose in an attempt to free himself from mortality and become a Heartless and Nobody, things which do not age, do not die of natural causes. I'm also under the assumption that his Heartless was merely Master Xehanort while his Nobody, Xemnas, was what was left of the empty shell of Terra. The transformation to a Nobody may have caused his Memories to return, however, as a Nobody that strong tends to retain Memories of its past self.
I had a lot more but forgot much of what I was gonna add as I typed. >>; A bunch of the glaring holes were probably filled in before I started typing, so point them out and I'll scramble to fill them in.
So that's it. o.o; Also, please don't comment anything along the lines of "we'll have to wait and see" :\ Those posts bug me.
tl;dr: Master Xehanort molded Terra to be his Vessel for when Kingdom Hearts was completed and he jumped bodies to avert death.
Disclaimer: Yes, I am fully aware of the insane lack of evidence for any of this, hence why it is considered wild theorizing. :3
Kingdom Hearts. We don't know exactly what it does, but I believe Master Xehanort knows exactly the extent of its power and intends to use it in Birth By Sleep as a means to save himself from his own mortality in a way. He's clearly old, possibly on his last legs, and he's looking for a way out.
Here's where it gets nuts and will probably elicit many flames. I think the third chair in the room where Erauqs announces the Master Qualification Exam belonged to a now-deceased Master, who was killed by either Master Xehanort or his apprentice, Vanitas. The Exam is designed to find a fitting replacement for their deceased comrade, and Terra and Aqua are the two closest and best prepared Keyblade Wielders to undertake the test, so it will be one of them. I don't believe Master Xehanort cares much about who gets the seat, just that the test has begun.
He was trying to get Terra away from his Master so that he (Master Xehanort) could convince Terra to fall to Darkness.
Why?
Master Xehanort was preparing Terra to be his new Vessel once Kingdom Hearts is complete.
I theorize that Master Xehanort's Soul orchestrated or incited the Keyblade War however long before Birth By Sleep it took place in order to generate a Kingdom Hearts for a similar purpose earlier, which placed him in the body in which he resides in Birth By Sleep. Perhaps the results of this body jumping caused the body to age much more rapidly than it should have, thus causing him to become much too old much too quickly. This also may have been the result of the original owner of the body struggling against the parasitic Soul of Xehanort.
I believe Master Xehanort was initially planning to utilize Vanitas as his Vessel, but Xehanort ran short on time, as his body would soon be too old and frail to support him any longer and Vanitas was still not strong enough to support his Soul, so he turned to Terra.
So, then, at the end of Birth By Sleep, Master Xehanort succeeds in his master plan, taking Terra's body for his own, though Terra's Heart and Soul stay with it, something Xehanort did not anticipate. This melding of Xehanort's Heart and Soul with Terra's complete being resulted in the both of their memories being delinked, with only the one overlapping memory, the name "Xehanort," remaining.
Perhaps, too, Xehanort indeed remembered much, much more than simply his name, though feigned ignorance of these Memories. He opened the Door to Radiant Garden's Heart on purpose in an attempt to free himself from mortality and become a Heartless and Nobody, things which do not age, do not die of natural causes. I'm also under the assumption that his Heartless was merely Master Xehanort while his Nobody, Xemnas, was what was left of the empty shell of Terra. The transformation to a Nobody may have caused his Memories to return, however, as a Nobody that strong tends to retain Memories of its past self.
I had a lot more but forgot much of what I was gonna add as I typed. >>; A bunch of the glaring holes were probably filled in before I started typing, so point them out and I'll scramble to fill them in.
So that's it. o.o; Also, please don't comment anything along the lines of "we'll have to wait and see" :\ Those posts bug me.
tl;dr: Master Xehanort molded Terra to be his Vessel for when Kingdom Hearts was completed and he jumped bodies to avert death.