Or maybe it's Master Eraqus pulling a Dr. Strange. He momentarily excercises control over Master Xehanort, chains everyone, and sends them to the Realm of Darkness as a sort of protection measure and leaves Sora alone, thinking this is the best move. Maybe this is Eraqus sacrificing all of his chess pieces in order to protect the best one: Sora.
Sora looks hardly like the best piece when he himself states he cannot go on alone without his friends, but who knows if there is a way to bring back lost pieces to the board.
I remember Nomura stating in the DDD Ultimania that no matter how often Ansem SoD was defeated/vanquished throughout the series he always came back somehow and there is a reason for that.
If the dark pieces can do that, maybe the light ones can too and if Eraqus is clever he's planning some sort of feint to probably bring back more than one light piece.
Only backdraft on this is that it means more pain for both the pieces sacrificed as well as the one remaining. Sora's scream in the trailer is loaded with despair and his entire movement and pose mirrors exactly the one Ventus does in BBS when Xehanort tells him about the X-blade and awakens some of his sleeping memories.
While this isn't exactly real world chess, as the dark side seems to have 15 pieces overall while the light side has 10 and the board is nothing like a true chessboard, there
is a rule in chess that pieces sacrificed are not necessarily gone for good as when another piece (I think it works only with pawns) reaches the opponents side of the board an own piece can be brought back
in whatever form the player chooses.
Needless to say that most players who do manage to pull off that feat (which is excruciatingly difficult either way) choose to bring in a second Queen, the strongest piece on the roster.
PS, speaking of the chessboard, it looks like there are "high-ground" fields on it that may grant some possible bonuses or something.
Further interesting is the placement of some of the pieces as at least four of the dark pieces seem to stand on a light field (namely the hourglass, cube, moon-sun and six-pointed star pieces) while the sole light one stands on a dark field.
The three pieces standing on the "high-ground" dark fields are obviously Master Xehanort (middle), Xemnas (left) and Ansem SoD (right) and one of the lying light pieces (the lower one having its foot towards the camera) seems to be Mickey's piece as a round mouse ear can be spotted to the left on the top.
Maybe it's Aquanort's grand entrance at the Graveyard.
0.2, which was supposed to be a prologue to KH III, went a moderate deal about how she was also able to use the chains.
Also possible although I think it is a less probable possibility than both Terra-Xehanort or Eraqus.
There doesn't seem to exist an Aqua-piece among the dark pieces unlike a Terra one which is shown to exist.
There is a possibility though it might be "Dark Aqua" unrelated to the Norts. Even if going dark I doubt that unless she's directly controlled by someone or no longer fully mentally there Aqua would ever willingly harm Ven especially if he's still in a sorry state, so if these chains come from Aqua it would probably be an action to
remove Sora and Ven from there rather than harm them or deliver them to Xehanort.
Hmm. You bring a good point. The possiblities are endless. Maybe it's also Vanitas, since Ventus was a student of Eraqus', and since their hearts are connected, he too can do it because his twin can? This is assumign Ven can.
Vanitas I doubt because of already two things:
1st it is never ever hinted that Vanitas can use techniques of Ventus just because he was created from him. Roxas and Sora also have their individual moves. On the flip side, Ventus too is never hinted at being able to use Vanitas' skills. The situation in the final battle was a case of a forced D-Link, not something that is active all the time.
2nd it is never hinted that Ventus can actually use these chains. He was not always Eraqus' student like Terra and Aqua are and Eraqus deliberately slowed down his training too.
Then again, when Ventus is using Vanitas' skills via the forced D-Links his own attack variants turn into Light-based versions of the dark-based ones Vanitas has so the precedence of those chains being a mirrored ability from one of the light-aligned characters is there as a basis.
Hmm, tricky, while I'm doubtful I certainly won't rule it out completely.
Going by the form of the chain links I'd stick for now with the theory that it is Terra-Xehanort having gained access to some of Terra's skill set.
