(I know, wacky forum-software at work, that's why I tend to write all my posts in notepad/Word first and Ctrl+C/Ctrl+V them over...

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Oh definitely, it is wonderful to see how some fans can make the storylines and characters even more loveable without completely changing their established traits and milestones, but some AUs and what-ifs (except those High-School or similar ones which are made just for shipping) also manage to keep the spirit so closely that it could be accepted as a legit KH entry.
Vexen out of all people? Lol, that's a really bold move to make considering that he apparently had no one he was really close with in the Org (except maybe Zexion, who also perished in C.O.) and it would make necessary an entirely different premise for KH 2. Without reading a word from it, lemme guess, the one who then actually becomes Roxas' closer friend in the Org after C.O. is Demyx?
I can see that point, and yet KH is neither the first nor the most origina workl in having two identical looking characters who are in fact distinct persons all
around. Nomura said he always knew from the beginning when he thought of the character that he should look either like Sora or Roxas, but wasn't sure with which one to go for quite a while (it's obvious that by the time KH 2 FM came around Nomura had made the decision).
Certainly you're right with that one, even more so since Ventus has received not really much attention outside of BBS except some cameos in other handheld titles and so far was also never shown together with Roxas.
Yea, that's practically what Nomura said, lol, if you pay attention you can differentiate them easily. But that goes for many things in KH and I guess that it is a phenomena of our current era that people have problems paying attention and are often no more capable of noticing subtle things.
Their wristbands having white, thick edges (Ven) and black, thin edges (Roxas) is also a nice little detail, but you need to know about it beforehand in order to pay attention to that and it is not exactly a physical difference.
The green eyes-thingy is actually something I would be totally fine with as it would be a small, but distinct physical difference to tell them apart. As Gram once said, the different colored eyebrows are a nice try but too secondary, especially since depending on the lighting brown can sometimes look like blond and vice versa.
So as it stands right now if Roxas and Ven would ever go skinny-dipping in the same swimming pool one couldn't tell them apart at all.
Not to mention that green eyes would totally fit Ven's wind theme and since I've seen some gifs with this I think he looks just s cute if not cuter with green eyes. Now give Terra brown eyes to fit his earth theme and the BBS trio would have a great diversity in eye colors.
Sora and Vanitas are really easier in that vein due to eye and hair color (although I do wonder when the golden eyes are indeed Xehanorty-trait and Vanitas gets freed of them somehow, will his eyes turn blue as well like Ven's and Sora's?)
That's a possibility indeed, it's also very noticable with Riku's design evolution as he's arguably the only one of the younger characters whose anatomy became more realistically proportioned with each instance.
True dat, Xehanort does it with more "style" and less "sloppy" than Aced, although even counting all that and definitely acknowledging that Aced has a problem with his temper I'm still reserving my final judgement on this character until I get a fuller picture of him. Xehanort on the other hand, I'm itching to finally do that damn old bastard in with all the stuff he has done throughout the series, not even counting the stuff he will undoubtly pull in KH III itself before it's (hopefully) finally paytime.
Holy Chirithy...hahaha, that's so cute. Cloudskating Gula.
That's the answer to the question "Where did Gula jump to in the finale of X[chi] after fighting Player?"
There is a thunderstorm going on through all the battle and according to the design of his Keyblade Gula has an affinity for the thunder element, so he could theoretically really ride one of those dark clouds overhead.
Imagine during their training with the MoM before all that whole chi-stuff Gula skipping lessons by cloudsurfing, lol.
MoM: "Now, for todays lesson..."
Luxu: "Wait Master, where's Gula?"
Invi *deadpan*: "It is cloudy outside, you have three guesses."
Ira *sigh*: "Not again."
Ava just chuckles.
Outside, Gula is flying by the window on a cloud.
Gula: "Yaaaay, freedom."
Aced: "God damnit, come back in here, you little shit!"
Sorry, just got carried away, lol.
Indeed, indeed, it also speaks for Gula having a strong will to live, even despite his own words to Skuld that "nothing matters anymore".
Oh, I'm also on the impression that none of the five Foretellers is in fact truly antagonistic or "evil" as some would say (since wanting to end the world can be considered very evil), but I am also on the impression that they all played their part and were perhaps "the traitor" at different points in time during the whole crisis. It wasn't Ava alone.
There is no denying though that there IS someone or something who uses the power of darkness to wreak havoc (and create black garments among other things) and bring about the apocalypse willingly, and that force is arguably the "true" traitor to the world and all who live in it.
This is also a possibility as well, since we so far know only snippets from the Foretellers (due to X[chi] and Unchained being players pov and the trailers being vague) we can't make a coherent chain of events yet.
I'd say the actual casus belli is truly the mistrust and evermore escalating animosity between the Foretellers and their unions as well. We see normal wielder kids almost getting at each others throats in broad daylight eventually (makes me wonder where their Chirithies are and why they don't interfere as Player's Chirithy does) and Aced states in the second to last browser update that he will wait on the "fated battlefield" which is an indicator that the bell serves just as a starting signal like for a marathon, akin to "NOW you can shed all restraint and actually bash each other's heads in".
It's just an assumption but I'd think that the bell ringing actually might also signal that the forces of light and dark are perfectly equal right now, ushering in an attempt to forge You-know-what, but without any of the wielder kids or even the Foretellers knowing.
Heheh, of course, that was just the strategy gamer/armchair nerd in me coming through. It is practially a huge free for all anyways and they all just charged in mindlessly anyways, which does make me wonder, do the wielder kids just indiscriminately slaughter each other on the spot? There aren't any uniforms in place (except if we count the union armor avatar parts, but the NPCs in the war scens aren't wearing them.) so how do they discern who is actually a wielder from their union? Wielder kids who are from the same party most likely know each other well and won't attack each other, but what about the other union members from other parties?
Asking beforehand which Union can be a deadly mistake so does that mean even kids from the same union start eventually killing each other?
Piles of dead bodies and blood like in the Battle of the Bastards in Game of Thrones would certainly have satisfied those who are on the opinion that KH needs to be more grimdark and graphic in nature and more akin to what it would look like in reality, but Disney would never put up with that and it also more or less goes against the established norm of the series. The darkened, dead Keyblades falling around everywhere pretty much symbolize the grave situation good enough and if we keep in mind that except three of the Foretellers all participants are either kids or youths in their early/mid-teens it is probably better it is not shown more graphically.
Depending on how it exactly ends for the Foretellers themselves, I could actually see at least some of them despair over the sight when they realize what has happened all around them and that they are more or less guilty for it.
In the one KH Trailer about the Lost Masters Xehanort does say that they were the ones who started the Keyblade War. At first, duie to the background being "greed for light and its ownership" it looked like they would be all greedy, evil assholes, but by now it looks more like they are tragic figures.