In case you didn't get this post may have some spoilers so read with caution.
Like many of us, I've watched the ending of 3D and I've been really fixated by the statement, “the 13 Darknesses will have to face the 7 Lights,” (or vise versa I'm sure the content is the same both ways). Even since this new statement was brought up I started scratching my head at the idea of who/what the 13 darknesses and the 7 lights were. Now numerous people have come up with the theory that the 7 Lights are the 7 keyblade wielders:
Sora
Riku
Mickey
Aqua
5. Lea
Ven (?)
Kairi (?)
For Kairi, Ven and also Terra, I'm not too sure about. I know the Secret ending hinted at Kairi being a big part and she is a keyblade wielder so it does make sense; however the one thing that doesn't make sense is that she is a princess of heart which would make her one of targets Xehnort is after, so why would anyone risk putting her into battle. I will elaborate more on this point in a little bit.
The only reason I question Terra is because of his heart being locked in it's own battle with Xehnort so for the sake of it I will say that he is not included in the 7 lights because Xehnort is counting him out already. I mean logically thinking if you took over someone's heart and had a sadistic mind like Xehnort wouldn't you feel a sense of confidence in your own power?
Now Ven is a little easier to believe. If he is asleep and his heart is resting inside Sora, then once his heart is returned to him and he is woken up then he should be counted amongst the 7 lights. This leads me to question, what about Roxas and Xion? Now Xion is easy to see why she would not be counted among them; she is essentially the broken memories of Sora's heart; therefore if she was to somehow able to join the battle, she would not be considered an actual Keyblade wielder since her ability to wield the keyblade was solely obtained due to her status of being a replica. For Roxas on the other hand, I'm not entirely sure. As I usually find myself doing when it comes down to matter of Roxas and Namine I consult this one theory that actually made a bit of sense:
http://forums.khinsider.com/handheld-entries/149593-roxas-namine-revisted.html
(yes I used khinsider but this theory kind of gets you thinking a bit more. Please read it in order to fully understand where the rest of this theory leads. Shall we continue?)
Now according to Gelandporn (formally known as Grass), Roxas has a part of Ven's fractured heart within him. This makes sense seeing that Roxas does display a range of emotions that a normal nobody would lack and his appearance is kind of a dead hint at Ven being a part of him. Now if this is true once Roxas and Ven finally join together then Ven will be the Ven we knew in the beginning of Birth By Sleep and would be counted among the 7 lights.
Now back to Kairi. How can she as a Princess of Heart be recommended to go into battle with the 13 darknesses especially if she herself is harboring one of the seven scattered pieces of the X-Blade? This had me thinking for quite some time now and while re-reading Grass's theory it kind of hit me. What if like Grass/Gelandporn suggest is true, “Namine is a personified fragment of Kairi’s light containing the spell Aqua cast on her. When Namine returned to Kairi, this completed her.”
Now where I'm going with, think back to Hollow Bastion that whole mess that went down when the Keyblade to People's Hearts released Kair's Heart from Sora and presumably created Namine in the process if what Grass/Gelandporn suggest is the correct assumption then maybe the fragment of light that was extracted from Kairi was the exact fragment of the X-blade which in turn would make Namine the one unknowingly holding the X-blade fragment and in a sense protecting it from Xehanort due to his lack of knowledge of her possessing it because to him, Namine is the nobody of Kairi.
I probably missed some key things while comparing this theory to the new information provided for us by 3D but I encourage you to at least read the first post in the theory; however throughout the thread she does make other points in order to elaborate on her theory making it even more plausible. Well that is a theory that I give credit to Grass/Gelandpron for thinking up.
Now onto the 13 Darkness which is something I haven't really put much thought in recently, I wanted to get the 7 lights out of the way first before tackling the more vague “army” for lack of a better name. From what I've gotten out of this I can infer that all forms of Xehnort will be present in the battle:
Master Xehanort
Apprentice Xehanort
Young Xehanort
Terranort (I'm not sure if he would be considered the same as AX)
Xemnas
Ansem Seeker of Darkness
Briag
Isa
Vanitas (?)
Mysterious Figure (? yet again not too sure if he would be counted as another Xehanort)
Maleficent (? why not I mean she's willing to do anything to conqure to worlds so we can't exactly put it past Xehanort to recruit her)
Pete (another possibility I mean we all know what Maleficent does he does too)
Heartless, Nobodies and Unversed (clearly towards the end of this list I've run out of ideas)
I'm trying to think is there anyone else besides Ansem the Wise who has golden eyes because I feel like the golden eyes would give a hint as to who is included in the 13 darkness.
Now I open the floor to all of you. I apologize for this being so long and I thank you for taking the time to read all this mumbo jumbo