The massive Dragon Overlord Babylon is the oldest Overlord in the cosmos and once ruled over it all. His wisdom and size gave him an advantage over almost everyone else. He used to have near limitless mana power when he was younger but lost it all when he was cursed by a mysterious being known only as "The One". The strain of resisting the curse left him battered and a shadow of his former self. From there he slowly wasted away over millennia eventually becoming senile, forgetful, and half-blind. He does command some degree of respect from the other Overlords even the egotistical Zetta.
Zetta time travels back to when Babylon was in power and defeats him. By this it is revealed that it was Zetta himself who defeated and took much of Babylon's power making him 'The One' though this contrasts Ophelia's statement of her being the same being. It is hinted that Babylon's power loss was due to the psychological effects of him losing to an unnamed opponent and that he never really lost his power but rather became depressed after his defeat and allowed his powers to diminish.
Source: Wikipedia, "Makai Kingdom: Chronicles of the Sacred Tome," available under the CC-BY-SA License.