In Omega's first appearance, it was ambling around the Cleft of Dimension as an optional boss you could fight on your way to Exdeath. We'll probably need to go inside something else to fight it (a Bend in Time?), rather than the current pattern of fighting a "heart" inside the larger being.

On the one hand, it's less "epic" scaled from the outside. On the other: something that (relatively) small took down the dragon Lousoix died (failing) to defeat. That was the size of a small moon. What iLv do you need to survive a hit from something like that?