
Originally Posted by
Spira
hmmm i cleared the game a second time (this time with min/maxing for Noel/Serah) and that kinda helped me clarify the story.
Caius knew all along that killing Etro would release Valhalla's chaos into the world, creating a timeless place. This was his intention to save Yeul. Yeul knew this, which was why she asked Serah and Noel not to pursue Caius that way. When she said she couldn't see the future anymore, it must have been because the future would have been a place where time doesn't exist.
If Serah/Noel didn't intervene at 500AF, Caius would have crashed Bhunivelze, created by 4XX af Academia, destroying humanity. But ultimately, the same things happened. Caius wanted to destroy time and ultimately succeeded.
his initial intention was to get the gate to open itself wide and let chaos seep out, when a lot of people die.. which failed numerous times. this would have been a scenario that happened if cocoon fell in 0AF, an ideal that the Cocoon fal'cie themselves desired. strange how they aligned that way.
that didn't work, so he would have to kill the goddess to allow the chaos to flow out from valhalla into the seen world instead. that was why he was fighting lightning in valhalla. and eventually, he won.
at the same time, he wanted to get someone strong enough to kill him to release this chaos from this heart - and this was supposed to be Noel. for some reason he is unable to kill himself to release the heart of Chaos. but in the end he kinda brought himself to do it, but still with noels help.
the ending you see is basically the result of his work. everything plays into his plan. Etro is dead, the seen world becomes an eternal paradox because time no longer exists and Yeul is saved.
Serah may be dead, but if time is warped, then the seen world is no different than Valhalla, whereby there is no such thing as life or death. By that same reasoning, there is no reason to believe that Caius or Lightning are dead either.