Quote Originally Posted by Toranja View Post
I ran the Praetorium today, to help a friend, and I used the opportunity to watch all of the cutscenes there again. This time, when the camera was passing through Ultima Weapon's tail, I noticed that it actually resembles a dragon quite a bit. In fact, the texture resembled Bahamut's to an uncanny degree.
Take a look at the Ultima Extreme preview from the last Live Letter: http://youtu.be/_x_To8MeloI?t=1h51m35s

Unlike the other HM and EM primals Ultima Weapon actually has a completely new model. His armor is missing (presumably destroyed by our last fight with him) revealing that he does indeed seem to have a draconic origin. He also has wings now... Judging by the pulsing red elements of his body though I'm going to go with him being some sort of hybrid of dragon and magitek.

We know from coil that the Allagans were experimenting with controlling the dragons using magitek, and at least attempted to enslave Bahamut, so I wouldn't be surprised if Ultima Weapon was another branch of their research into some kind of cybernetics. The Heart was likely the missing piece of the puzzle so to speak.