"Primal Gathering"

[Shougun]

Here is what I meant (it's a bit different than the purple one by Duuude007, I think the white on the bottom is just smoke). I've put an arrow at the right horn that appears to be in the fog, however it might be a result of the OPs photoshopping - it's much harder to see in the original. There is writing on top of where the left horn would be to the bottom left of leviathan (I drew that dotted horn a bit big now that I look at it). The middle horns/crown would all be behind the other primals.

original images to compare

But if that right horn is from the OP's photoshopping and not in the original, then I would say it's not Atomos. It's only a "what if" based off an unclear photoshopped image, so I'm just acknowledging it's possible. I do believe Atomos will play a bigger part in ARR though, even if it's not in this poster.

I wanna draw lines!!

(white dots are just lazy right clicks with teh eraser :P)
Really looks like the six opposite primals are working to pull open some sort of rift that is pulling in Bahamut while Odin is at the lead of the event.

Whatever it is I think it has a lot to do with Bahamut being imprisoned - and due to the "gravity" / sucking perspective I think Atomos is a good argument. Too bad we can't see behind Odin - might help XD..