Ok, so I really do believe that MX was able to possess Terra's body by making him exploit the darkness that was slowly growing in his heart. I know, I know, the theory's soo unoriginal and overused. But hear me out, people. Here's what I think happened.
So, near the end of Terra's story, the darkness has all but completely consumed Terra's heart due to MX persuading him to use it more and more. Why does MX want Terra to exploit the darkness within him? So that he can take control of his body. Why does he want to take control of his body? Well, he's obviously growing old and most likely does NOT want to die just yet. Plus, since MX and Terra are both Keyblade wielders, he probably believes that he will be an even stronger master if he takes over his body. These are things you've probably read about already.
However, when MX finally does attempt to take control of Terra's body, Terra tries to refuse him and not let him take control. Terra's heart was very strong at this point, stronger than MX's, and because of this, a whole new being with a whole new heart is created. Who is this new being? Why none other than Xehanort, ATW's first apprentice.
Wait, if Terra and MX were both keyblade wielders, how come Xehanort can't wield one? Well, as I said, a completely new being with a completely new heart was created due to MX trying to take control of Terra's body and heart. However, some of their abilities are still present inside Xehanort, as ATW noticed, since he seemed to have "superhuman abilities" according to one of his reports.
Where did the memories of MX and Terra go? Well, they didn't just disappear, but rather, they were hiding in Xehanort's heart. That's why he appeared to have no memories, other than the name Xehanort, which was only remembered because of Terra's deep hatred toward Xehanort for making him use the darkness.
Further proving this, we have Xehanort's Heartless and Xemnas. XH has the exact same clothes as MX has, save for the Heartless symbol on his chest. Why is this so? Well, when Xehanort turned into a heartless, we can say that his heart essentially "split in half". That is, the half that was MX pretty much went to XH and the half that was Terra went to Xemnas. Also proving this, Xemnas seems to remember a lot about Aqua and Ven, such as Xemnas calling Aqua a "friend" and saying that Roxas was "sleeping again" in 358/2 Days (most likely referring to Ven) However, the memories of MX went to Xemnas as well, since a Heartless has no memories of its past life.
So, why does Xemnas only seem to have Terra's memories? Where are the memories of MX? Well, as I said earlier, when MX tried to take over Terra's body, Terra's heart was stronger at the moment when Xehanort was created, so therefore, Xemnas only seems to have the memories of Terra. However, the memories of MX were sleeping inside him somewhere instead of just going away.
So, what do you think? I'm open for all criticism.
So, near the end of Terra's story, the darkness has all but completely consumed Terra's heart due to MX persuading him to use it more and more. Why does MX want Terra to exploit the darkness within him? So that he can take control of his body. Why does he want to take control of his body? Well, he's obviously growing old and most likely does NOT want to die just yet. Plus, since MX and Terra are both Keyblade wielders, he probably believes that he will be an even stronger master if he takes over his body. These are things you've probably read about already.
However, when MX finally does attempt to take control of Terra's body, Terra tries to refuse him and not let him take control. Terra's heart was very strong at this point, stronger than MX's, and because of this, a whole new being with a whole new heart is created. Who is this new being? Why none other than Xehanort, ATW's first apprentice.
Wait, if Terra and MX were both keyblade wielders, how come Xehanort can't wield one? Well, as I said, a completely new being with a completely new heart was created due to MX trying to take control of Terra's body and heart. However, some of their abilities are still present inside Xehanort, as ATW noticed, since he seemed to have "superhuman abilities" according to one of his reports.
Where did the memories of MX and Terra go? Well, they didn't just disappear, but rather, they were hiding in Xehanort's heart. That's why he appeared to have no memories, other than the name Xehanort, which was only remembered because of Terra's deep hatred toward Xehanort for making him use the darkness.
Further proving this, we have Xehanort's Heartless and Xemnas. XH has the exact same clothes as MX has, save for the Heartless symbol on his chest. Why is this so? Well, when Xehanort turned into a heartless, we can say that his heart essentially "split in half". That is, the half that was MX pretty much went to XH and the half that was Terra went to Xemnas. Also proving this, Xemnas seems to remember a lot about Aqua and Ven, such as Xemnas calling Aqua a "friend" and saying that Roxas was "sleeping again" in 358/2 Days (most likely referring to Ven) However, the memories of MX went to Xemnas as well, since a Heartless has no memories of its past life.
So, why does Xemnas only seem to have Terra's memories? Where are the memories of MX? Well, as I said earlier, when MX tried to take over Terra's body, Terra's heart was stronger at the moment when Xehanort was created, so therefore, Xemnas only seems to have the memories of Terra. However, the memories of MX were sleeping inside him somewhere instead of just going away.
So, what do you think? I'm open for all criticism.