Omega Weapon?

[Kaiser-Ace]

The original Omega (the robot spider thing) is hinted at being the same entity similar to Gilgamesh (or at least the same description)

http://finalfantasy.wikia.com/wiki/Omega_(Enemy)

Hmm, that would explain how there are only 4 aperences of the Biological Omega Weapon while the Mechanical Omega is one of THE most recurring superbosses in the FF series along side Seiryu and Gilgimaesh him self, the very name sake for the Paradox that involves the three "Rift Wandering" beings.