So, after seeing the new trailers for KH3 and the reveal of Dark Aqua, it got me thinking back to DDD.  When Master Xehanort tells Mickey and Riku about the Seven Guardians of Light and Thirteen Seekers of Darkness, Mickey thinks about who they are, counting himself, Riku, and Sora, and their 'three missing friends', who would be Aqua, Terra, and Ven.  However, Xehanort responds by saying that Sora and another on the list belong to him now.  Now, when first seen everyone assumed he meant Terra.  But, what if they're wrong?  What if, by defeating Ansem and Xemnas, both Master Xehanort and Terra returned to their full bodies, and Terra was able to break free?  And so, what if the 'another' that belongs to him is actually Aqua, having finally succumbed to the Darkness after spending so many years in the Realm of Darkness.  At that point, I imagine it'd be so simple for Xehanort to transfer his heart into her.  What do you guys think?

Wasn't Aqua struggling with hallucinations of Terra in the RoD? She obviously was succumbing to the effects of being exposed to darkness for so long. Aqua's heart being close to Terra's and Terra being possessed by Xehanort makes a enough of a connection, especially in the RoD, to be influenced to Darkness. I agree that if she hasn't simply turned to Darkness herself, she may have been possessed by Xehanort. 

I'm not sure about your theory, but the fact that Xehanort says : "But Sora and another on your list belong to me now" does make it plausible.

 

I think it all comes down to how Xehanort is back in his original form and not his Terranort form. Nomura has said that it will be explained in KH III. So I can only see two cases :

1) What you said, Xehanort and Terra split. So, Terra is somewhere out there and Xehanort could be talking about Aqua or Ven. We don't know how long Aqua has been in the Xehanort form. So, for all we know, she might have been one of the hooded people in DDD's ending .

2) Xehanort had taken full control of his Terranort body and the "Terra side" of him was completely wiped off. That would mean that Xehanort is talking about Terra and not Aqua or Ven.

 

The Xehanort we saw could have time-travelled but that wouldn't make a lot of sense.

Edited June 13, 20187 yr by Nick Sideris

If anyone recalls,in the opening for A Fragmentary Passage, towards the end Aqua is seen underwater and in her eyes we see a reflection of Sora in his KH3 outfit and his hand is reaching down for Aqua to bring her up out of the water. Seems to me symbolic of Aqua being lost in Darkness and Sora being the one to bring her back. Every KH intro has used water and being underwater metaphorically in some fashion, Sora in KH1, Roxas in KH2 both had points in their journeys where they were exposed to Darkness, yet overcame it. Chances are this is exactly what Aqua is experiencing.

 

I also wouldn't overlook the fact that Aqua may have a Nobody by this time, her heart has spent enough time in the RoD and she is seen struggling with Darkness throughout, so that could be another factor here.