Allrighty then...let's make one big comment on this very interesting becaus very developped theory (by the way, I suggest you check mine). First of, I believe Sunset Horizons (the KH2 Secret Ending) happens in the future, and that the three knights are Sora, Kairi and Riku, wearing Ven, Aqua and Terra's armors. This is why the keyblades they pick are not found in Birth by Sleep (the KH2FM Secret Ending, which happens in the past), and why Nomura said the secret endings happened both in the past and the future. I agree with the similarities between the three knights and the Destiny Islands trio, however I have different ideas about the keyblades they pick in Sunset Horizons : -Kairi picks up the Inverted Kingdom Key because it is associated with darkness, and because she comes to the crossroads from the road to darkness : my guess is that she confronted the darkness as a trial to awaken her power. As a Princess of the Heart, her heart holds great power since it is pure light : it is this potential that enables her to use a keyblade, and that could make her a heroin for the game. -Riku picks up the Kingdom Key because it is a symbol of light, which he needs to defeat the darkness within him. Those darkness would be linked to the return of Xehanort's heartless, which we both thought of. -Sora picks up Way to the Dawn because he has come to realize he is influenced by darkness as well : this is manifested in Anti-Form, and what he says at the end of KH2 about the fact that darkness may have seized him as well. The keyblade will help him face and control his darkness. Those are only vague ideas and speculations, with not much to back them up. I find your theory about Ven (his relation to Sora, Roxas and fate) really interesting, although I can't say I agree with it : it does find an explanation for the quotes and the theme of fate, but there's not a lot to back it up. It would make sense, but it's a subject on which there's not a lot of real clues. About how Aqua and Terra are protective of Ven, I don't quite agree with you : Terra could hold Ven back because he wants to be the first to attack (since he hates Xehanort so much), and Aqua is very protective of them both (the Reflect she casts on Terra and how she saves Ven from the fall). It's normal for them to look worried when Baldy catches Ven : if they're friends, to see one of them at the enemy's mercy is bound to make them worry. About the relations between Terra and Xehanort, I agree almost completely. I don't think Baldy is named Xehanort (that would make him not a new character, in a way) ; my guess is that Terra's eyes turned yellow because he was about to use darkness, which Baldy then used as a doorway into him, in order to possess his body, exactly like Xehanort did with Riku. And about Terra being Xehanort's "avenger", I think it's a mistranslation, and that Terra is not seeking to avenge Xehanort, but to exact revenge upon him, probably for what he did to Ven and Aqua. Xehanort would then be Baldy's heart and mind in Terra's body. About Riku and Axel, I'm sorry, but Riku's eyes are still turquoise in KH2, and I'm sure of that. They do share the gesture, and that's significant : it comes back in KH1, then in CoM, then in KH2 (in the opening, and in the ending, when Sora says "We'll go together"). It always represents an invitation, showing a position of superiority : Riku not being afraid of darkness and of leaving the island, Axel knowing more than Sora about what going on in Castle Oblivion, and Sora having more confidence than Riku, who's still in doubt about his nature. I don't know if its is significant that both Axel and Riku do it, maybe it's just to suggest the similarities between Sora and Roxas (Axel being Roxas' best friend, just as Riku is Sora's). But I don't think it means there's a strong link between Riku and Axel : he can't be Riku's Nobody, since Riku never lost his heart, and since they are nothing like each other (not the same physical appearance, not the same personality, not the same element of affinity...). So that's about all I had to say. A very good set of thoughts and theories, which will probably give us a thing or two to talk about in the Discussion of Secret Ending topic.
Sora can't possibly have remained a heartless until the time he merged back with Roxas : a heartless is a heart enslaved by darkness, and could never use the keyblade, which apparently requires a heart worthy of its power. Rather than a heartless, I'd say Sora existed only as a heart until he merged back with Roxas : somehow, he was powerful enough to create a new body and a new mind for himself until he could get the originals back and be complete again. About Xehanort's origins and identity, that's something we've been speculating on for quite some time : one of the most popular theories is that Baldy took Terra's body for himself because his own was too old, but that somehow he lost his memories in the process. The ES Sora fights in KH2FM would be either Terra's heart or his memories that went on to exist on their own, and that hate the man named Xehanort, because it is his body and his enemy's heart and mind.
Like you hinted, the yellow KH is probably linked to darkness (like yellow eyes), since it was formed in the dark realm. The blue KH would probably be linked to the realm of light, linking it also to this original world.
I personally think the Terra we fight is not the Terra in the secret ending, since I believe his body was taken by Baldy. But apart from theories and personal opinions, I think we can all agree on one point : Terra has a weird behaviour when Sora meets him. He talks in erratic words and fragments that make it seem like gibberish, and he says all he has is hatred, as if he was made of that emotion. That reminds me of a ghost, lingering in the world of the living because he still has one thing left to do, and driven only by this thing, here his hatred of Xehanort. When you add this to the resemblance between Terra and Xehanort, you get to the idea that the Terra we meet as Sora is only a fragment of the original person, a ghost or a shadow. From there, wether it's his memories, his heart that was cast out when Baldy took his body or something else, is just speculation.
In Com, we saw that even losing his memories, Sora could still follow his heart and retain his true personality. The question is : will Terra be different, and will the nex game's possible darker tone affect this matter ? About the "healing their pains", if the translation is accurate, it basically means : "do not return to the healing of their pains", which implies he (or her) had already started healing their pains. It does not mean "do not return in order to heal their pains", it's more subtle than that.
http://www.gamefaqs.com/console/ps2/file/915410/42388 Look at the Anti-Form section, it explains how the count functions.
I personnally think they're at the crossroads (yes, the same we see in Chain of Memories), after the last great battle of the keyblade war : that's why there are so many keyblades, why they form the crossroads and why the landscape is so barren (the battle has unleashed so much destructive powers it has made those green meadows a barren desert).
That's probably a nickname for Xehanort...no the keyblade she picks up is hers (it looks nothing like Riku's fake keyblade), and Baldy's isn't Oblivion either. Just look at Baldy on kh-vids.net's banner. In my wildest fantasies, I imagine that the presence of those keyblades means Cloud, Leon and Jack Sparrow (sorry, Captain Jack Sparrow) will have keyblades in KH3.
One last thing : if you find that you turn into Anti-Form too often, just turn into Final Form, it'll restart your Anti-Form count, and basically there's no chance you'll turn into it next time.
That keyblade (I don't know what its name is, I've heard Acrossing Two and Fateful Encounter...the second sounds better) has an ability that affects your Anti-Form count : basically it makes it so you turn into it more often, so you can obtain Final Form faster. I don't think it has any real use apart from obtaining Final Form, so I'd ditch it for Ultima or Oblivion if I was you.
It wouldn't surprise me if the voice actor for Xehanort and Xehanort's Heartless did Terra's voice, just to underline the similarity between them further.
For Master Form go to the Land of Dragons, at the Imperial Palace. The heartless in the place just after the door are loaded with drive orbs. Just use magic to take them out quickly, pick up the orbs, return to the save point and go to the world map while still in drive form. Lather, rinse and repeat.
Just one tiny tiny thing about the Tree of Life, Sephiroth is a plural, the singular is Sephira. About this whole trinity thing, it's really interesting indeed. I think this idea of a 3-person groupe can be found in many other works : take Naruto for example, in the genin teams there are always two boys, one girl, like with our Destiny Islands gang. That is very common is shonen and in mangas more generally ; in many shonen you have the two protagonists : the naïve and kind-hearted one and the serious, skilled and brooding one. That's Sora and Riku for you. Given that this always results in a rivalry, if not in an enmity, there's usually a third element in the team, who will bring balance to those two. If this third member is calm and reasonable, it helps, so usually it's a girl. There you have Kairi. The kind-hearted idiot, the "cool guy" and the reasonable one in the middle. The holy trinity of manga and many japanese works of fiction. You can find that in Berserk (Gatts, Griffith and Casca), Hellsing (Seras, Alucard and Integra) as well. And apparently that pattern is reproduced with the knights. Terra corresponds to Riku, so he's the serious skilled one, Ven (=Sora) is the enthusiastic naïve guy and Aqua (=Kairi) is probably the reasonable balance-bringer (you can see how the takes care of those two, with the Reflect on Terra and how she catches Ven when he falls).
We had a render of Aqua in a newspost not long ago, with her keyblade. And it didn't strike me as similar to Riku's fake keyblade in KH1...besides, it wouldn't make much sense, Riku made it with the hearts of the Princesses, and it's quasi-certain now the secret ending happens in the past.
I don't think you can really compare Riku and Axel : they're two completely different characters. I know the have the role of best friend in common, but I think their differences are important : it's one of the things that distinguishes Roxas from Sora, and makes him an independent being, his own man, with his personality, his existence and maybe even his heart.
The doors represent the crossing of the point of no return, as well as growth, entering the wide, hostile world of the adult. Destiny Islands represented the safe but narrow state of childhood, and it was destroyed and the characters cast out with Riku opening the door. Sora's will to enter the final door even though he knows he can't come back shows his growth and his gaining self-confidence...growing into the role of the hero, in a way. The theme of growth is really interesting in KH, but it's not the point of this topic. I'm afraid TwilightNight's right (wow, that was some rhyming), even though I think I'll keep discussing this matter.
With this "Master Xehanort's avenger, his name is Terra.", I'm seriously beginnin to consider this idea of Baldy being the knights' teacher...However, when it says avenger, maybe it was mistranslated and should be understood that Terra is seeking to exact revenge on Baldy : if you consider that Baldy is Xehanort in some way, it's coherent, since Terra said he hated Xehanort.
Well if there was one world in the beginning, it was probably Kingdom Hearts, since all hearts come from it, including those of worlds. I wonder...is there a place where keyblades all wait and choose a heart once it becomes worthy, or is a keyblade created each time a heart becomes worthy ? The keyblades in the secret ending linger even though their masters are not here : that probably means something important. My guess would be that Baldy's making them remain, because he's using their power for whatever goal he has. In my opinion there is one true, natural Kingdom Hearts, which is the place where all hearts come from and to which they return after their shell dies. XH was collecting the hearts of the worlds and Xemnas the hearts of the people, but both were searching for the same thing : a pathway into the real Kingdom Hearts, which is a source of tremendous power, since it contains so many hearts. Baldy is probably doing the same thing : he's building a fake, artificial Kingdom Hearts from the powers of the keyblades in order to obtain the real Kingdom Hearts. However, if in both games Sora and co. seem to have witnessed or entered the true Kingdom Hearts, it's never been made clear. In KH1 it had the aspect of a gigantic door in the void : once opened, it released a flash of light, probably coming from the hearts in it. But then, on the other side of the door we saw the realm of darkness. In KH2 the Huge Door Strikes Back (imagine Xemnas saying : "Sora...I...am your father" the worst is that the voice fits, and seeing as Terra is from the past and seems linked to Sora and Xemnas...could it be possible ? Nevermind), and again what we see on the other side is weird : it's essentially some buildings which Mansex enjoys throwing at you, a colorful void, and a black and white inconsistent dance floor where Mansew plays Mr. Zebra...why not ? But the problem is, once it's all over, Sora and Riku find themselves in the realm of darkness again, near the border with the realm of light. So what is Kingdom Hearts ? Is it only a door ? It's obvious there's more to it than we've seen, but so far there's only a big door, some light and weird void spaces that seem to be linked to the realm of darkness.
That thing about the different keyblades is quite interesting...imagine Cloud, Leon and Captain Sparrow getting keyblades during the war...how sweet would that be ? There definitely is a link between the knights and the Destiny Islands friends, the names confirm it. Naminé contains the word "nami", which means "wave", that's how she's connected to Kairi (which is related to "sea"). As for Roxas and Axel, I doubt there's any special meaning there, sorry.
The yellow eyes may be an inevitable physical sign : the really bad consequence is the impact of darkness on the heart. Nobodies may have orange eyes because they use darkness a lot, but it's only affecting their bodies, not their hearts, obviously. Are you really asking this ? In the game, it was revealed by the King and by a flashback that Xehanort was Ansem's apprentice. I've checked the flashback conversation between Mickey and Ansem...and I can't say if his eyes are orange or brown. Even when you're close to his face, you can't be certain : at least I can say that if they were orange, they weren't as orange as they were when we saw him as DiZ (that was one weird statement...).
