but nobodies are capable of thought even when they don't have a heart.
That's because they have the memories from their human life from before. Memories are an integral part of the heart (and therefore the spirit) and help the Nobodies to form their personalities.
Roxas and Naminé are the only excpetions to this and that's also why they are so different from their original personas. They had to develop completely from scratch and create their own sense of self by creating own memories. That is seen in the very first part of Days when Roxas is "Zombie-like" and at first can't even speak.
yes, it was. but that is not a very specific statement. Shadowy other? what does that mean? it could be that they were avoiding being too specific so that it could be a good plot twist in kh3. also, they didnt even have to mention the "shadowy other" they could have just said "defeat Xehanort!" if its not important to the story, then why wasn't the guardian in the battle from the start? why would they make a point of stopping halfway through the battle to show it coming out of terranorts chest? before the battle started, terranort said "terras heart has been extinguished; smothered by the darkness within him!" maybe his heart wasn't "extinguished", but maybe it was smothered by his darkness, and it had become a heartless. also, the part of the scene at the end of kh3d where the guardian grabbed riku and mickey and donald and goofy came in to save them was almost pointless, unless it was too get the players to notice the guardians presence with ansem.oh yeah! I meant to address this a lot earlier in the thread but i got sidetracked. I think that this part of the battle was more symbolic than literal. perhaps the gold shining in the background represents terras light, the pink sphere his heart, terras character model his mind, and the guardian the darkness of his heart. note that you can only get to the go to the gold dimension when the guardian grabs you, terranort doesnt have to be anywhere near you when you are grabbed for you to go there.
Without jumping directly into the realm of speculation, it means at least that it is a part of Xehanort. That's what the description gives us at point blank value.
I won't deny that the Guardian may have some story significance, yet it coming only half-way through the final battle is usual Square-procedure of a final Boss having several forms. Story-wise, Xehanort realized that he couldn't overcome Aqua with just his Keyblade and that she was trying to help Terra take back control, so he decided to up the ante in the battle as he clearly summoned the Guardian of his own volition.
That Terra's heart was "extinguished" was a lie on Xehanort's part anyways as we not only see it fighting back later during the battle, nope, we even see Terra's heart conversing with Xehanort's in Blank Points, which is also an indication Terra didn't became a Heartless because Heartless are not able to talk. Sora also couldn't talk as a Heartless and Ansem SoD isn't really a Heartless per se as evidenced by the Ansem Reports from KH 1:
Ansem Report 12 said:
I have transcended to an existence of only the heart. I should have come back as a Heartless, but there is no sign of such a transformation.
That Terra's heart was drenched in Darkness is out of the question, but it is highly questionable if it could be turned into a Heartless since it was captured by Xehanort's heart.
The creation of a Heartless includes the rejection of the body, as otherwise the Heartless could not spawn.
The scene with Donald and Goofy can have multiple reasons, including the one you mentioned, comic relief and giving them some more screentime so I won't rule that out.
Rather than symbolic I took it always as a dive to the heart, with the golden dimension actually being an awakening with Aqua and Terra working together to expel Xehanort's darkness (in the form of the Guardian) from Terra's heart with their dual limit. This is also reinforced by the Guardian having the same HP bar as Terra-Xehanort.
The Guardian is always connected to Xehanort and never detaches itself for good, so it represents the darkness that is holding Terra's heart and body captive, the invading darkness of Xehanort, so it's logical for Terra and Aqua to both target it in order to try and expel Xehanort. At least that's what I took from the scenes when I played BBS.
i dont remember hearing that you have to lose your heart to become a heartless. although that is what almost always happens, that doesnt mean that it has to be lost. they often say "consumed by darkness" and when they say "lost to darkness" i dont think they mean it that literally, but more like "lost control of it to darkness"
xehanort is very skilled with controlling darkness. his heart could have used this skill to call out to the darkness in terras heart and turn him into a heartless, which doesn't necessarily have to exist outside of a body. ansem SOD was a heartless and he existed inside riku's body for a very long time.
but this brings up a question: if terra was a heartless, how come his heart was normal looking in blank points?
after you beat terranort, he says "get out of my heart!" and then stabs himself. he was trying to remove terras heart, but obviously failed. however, the guardian did appear behind him, and then collapse into a pool of darkness which led to the realm of darkness. perhaps when xehanort tried to remove terras heart, he half-succeeded. maybe he separated terras heart from the darkness which made it a heartless, and that darkness is what appeared behind him, but without a heart being part of it's composition, it was just darkness which could no longer hold itself together, thus collapsing and creating a portal to the realm of darkness as a side effect.
*pant, pant*
For a Heartless to even come into existence the body needs to be rejected/the Heart expelled, that's what is meant to "turn" into a Heartless. You can lose your Heart without becoming a Heartless, like Riku and Ventus, but you can't become a Heartless without separating Body and Heart.
The Ansem Reports from KH 1 give also an answer to this as well as to the fact that the soul always remains with the body:
Ansem Report 13 said:
Heart and soul are separate, and the soul remains in the body. But can we assume that the remaining body and soul perish?
Certainly when the heart changes into a Heartless, the body disappears.
I agree that Xehanort can control Terra's body through the darkness and may even get partly control over his heart with it, but that doesn't equal turning it into a Heartless. Going by that logic, any of Xehanort's vessels would have to be a Heartless.
Exactly, Terra's heart in Blank Points also does not add up with the theory of him being a Heartless. As for why Xehanort failed to expel Terra's heart, we have no definitive information about that but a common fan-interpretation is that Eraqus's heart may have had a hand in it somehow.
All in all, I won't say it is completely out of the question, but with the current information available I personally find it to be unlikely.