Hey guys! I am the guy who created this image http://i.imgur.com/BriXYra.jpg for reddit, and I want to add some things I've thought since.
With the HD trailer releases, I can confirm that those pieces represent both Terra and Aqua. In fact, the question mark right next to Sora, may also be Terras. But why two of them? I may have an eplanation below.
The two pieces over Vanitas are, as you people already said, Xehanot's Guardian. I don't know how I missed that
The black piece over Eraqus side is probably also Vanitas, but I cant 100% confirm that. Even in the HD trailer is kindda confusing.
So I wanna take a closer look at the movements of the pieces, maybe they are hinting some future events.
In the minute 2:09 of the trailer (https://www.youtube.com/watch?v=IaTjCvUZjck): Xehanort says:
"On that land shall darkness prevail and light expire" Right after that, he takes one of his pieces and defeat one of Terras."The future its already been written"
Now is when Eraqus intervenes: "Who says I can't chage it? And maybe light will prevail" The other Terra's piece is shown at Sora's side, while this one takes care of the guardian (which is speculated to be very related to Terra) "There is more light than meets the eye. You might be surprised!"
"Well I hope so" The trailer ends with Soras and Xehanorts pieces facing eachother.
Would this mean that Terra will be saved by Sora, and being one of the 7 light? I was against that before the trailer, but I changed my mind. Also, there is no representation of Lea, which was speculated to be one of the lights.
Lastly, I want to speculate about that star seen in the black side (number 8 in this image http://i794.photobucket.com/albums/yy230/ShardofTruth/Other%20KH%20stuff/Chess%20Pieces%20KHIII.png).
It looks like a star, but it's not a star like we've seen before. The star we are used to with the paopu fruit and the lucky charms are 5-pointed stars, while this one seems to be 6-pointed. I've been crazy looking for a 6-shaped star in the KH universe, and the only thing I could find is this. The keychain from Unicornus keyblade. It does not resemble very much, if at all. http://th08.deviantart.net/fs71/PRE/f/2013/204/8/5/x__chi__keyblade_unicornis_by_marduk_kurios-d6dgyv9.png
But its 6-shaped and the chess piece has a hole in the middle, where the "eye of darkness" should be. Dont take my too serious on this one, I'm just exploring all the possibilities I can.
Anyways, what do you think? Oh, and sorry for my bad English
Keep theorizing!
Ok, so I have a little bit more with this movement. So, Eraqus says: "Who's to say I can't change it?" Right after that, he takes Sora's piece and captures the piece of the Guardian. Could this have any relationship to this? He will change it, using Sora.