posted by JL Lee at gamefaqs. it's long lol but interesting:
Having cleared the main story (NOTE: I have not reached the Secret Ending yet, and am in no position to reach it yet), read through the Fragment log and read/listened to the entire story, I am somewhat confident to lay it all out so as to make things less convoluted.
To those who have cleared the story as well, please correct any mistakes that I may have made in the process.
Let's start with how it all began...
Lightning
At the end of Final Fantasy XIII, Vanille and Fang sacrificed themselves to prevent the fall of Cocoon, which would have led to a major Catastrophe on the surface of the planet. Their objective complete, they began their endless sleep as crystals, as SHOULD HAVE BEEN for everyone else, seeing as L'cie would turn into Crystals once their original goal was complete.
However, the Goddess Etro, at the very last second, saw fit to use her compassion for the six heroes and the One who led them to it (+1 little boy) and released all of them (sans Vanille and Fang of course). However, what should have been the correct ending suddenly opened up a new frightening danger: The opening of the Gate to the Other World. By using her power directly to intervene, Etro consciously opened up a path leading to her world Vallaha, pulling Lightning into it.
Causing Lightning to be erased from existence.
At this point of time everyone's memories have been altered to think that Lightning was also imprisoned within the crystal pillar, but Serah, having been touched by the Goddess as well, retained her memories, and knew that something was wrong.
Enter.
Noel
Literally the last man on the planet, he is the sole remaining survivor of a desolate world, during AF (After Fall) 700. His race was the same race as the ancients, the Seers. Yet among his race, only one girl, Yuel, had the ability to glance into the future.
Yuel
The main focus of the entire story, a girl who, by the grace of the Goddess, was given the Sight, to be able to see a vision of the future, and with that vision, able to imprint it on a viewer so that future generations can be forewarned, and attempt to avert that future.
However, using the ability comes with a grave price.
Death.
Thus, for years upon years, centuries upon centuries, the Yuels, at the age of 15, will always get a glimpse of the future, and die thereafter. There is no escape from this "curse", and there is no way to stop her from seeing the future.
Upon her death, the body is returned to the Chaos that is trapped within Vallaha, to be reborn again as yet another Yuel so as to help the next generation.
She becomes the focal character in the feud between Noel and
Caius
The man who has lived for over a thousand years, the Protector of the Seer. There can only be one (yes Highlander) Protector at any one time, and that is because the Protector, aside from being able to be part of the Seers, has HALF of Etro's power, namely her heart, the Heart of Chaos. With it he does not age and he will be revived whenever he is killed. Each new Protector, when defeating the previous one, will have to have the Heart cut out and replace his own, in order to live and survive through time.
Caius, a man who used to be a L'cie thousands of years ago, as part of the ancient Seer race, who sacrificed himself by merging with Bahamut (the process kills the summoner), but again Etro saw fit to save him with the power of the Heart. With that, he has endured centuries of pain, tens, maybe even hundreds, of Yuels die.
His final resolve, to stop the curse by ending Time itself, forcing the Gates to open once again and let Vallaha into the world, so that time does not matter, so that Yuel cannot see the future and die again.
Why does he attempt to stop Noel and Serah then?
Because the premise of this game : time travel and paradoxes is that by Changing the Future, you Change the Past.
(Note: At this point of time Back to the Future is a good reference for everything GOOD about time travelling stories. In fact The 3rd Birthday did it quite well too. Everything from this time onwards is based on the FNC world mythology, so real-world physics does not apply)
By creating a paradox due to actions, by attempting to save the future, which was their ultimate goal in this game, Serah inadvertently creates alternate futures. Case in point, while attempting to clear the endless loop of Demi Fal'cie Adam changing the past, Serah shouts out aloud to Hope to stop the plan. An ancient Yuel sees this scene and imprints it, dying in the process. Hope sees the vision (as it was intended for him) and stops his plan, thus realigning the future into a path where they could prevent the death of the planet.
Along with every other Paradox side story (not entirely important), the Six Heroes are all brought to different time periods and worlds because of them being given a new lease of life by Etro.
Lightning -> Becomes the Avatar of Etro. Once she reaches Vallaha, she is able to see all that has happened and all that will happen, and knows that it's an endless war with Caius in which he can't lose, but she can. Her only option is to rely on Serah (see below) and Noel, who knows the future, and is able to guide Serah towards a different future.
(Note: Again, via any time-travelling logic, whenever they change the future, Noel technically should disappear since he should not exist, and everone's memories should have been heavily altered, but hey, that's going way beyond Paradoxes, so don't think too hard about it)
She becomes the guiding light for Serah to change the world and lead it to a better future, since she has transcended time, but due to Caius manipulations and ability to move in and out of Vallaha, she is eventually defeated right at the onset of the war (see: Prologue)
Sazh and son -> Caught in another time/space trap, both are sent to the Casino (which also exists out of normal time and space) as well as the Colosseum. Eventually makes it out (how? Not mentioned) and is able to retrieve Vanille and Fang's crystalised bodies from the weakening pillar in AF500, the designated time where it will finally weaken and Cocoon will finally crash onto the planet.
Hopeless - Spent 10 years as a researcher, eventually rising to the top. With his assistant Alyssa, he continues his attempts to recreate a new Cocoon so as to save the people for the eventual destruction of the planet.
His first attempt was to create an artificial Fal'cie, Adam, whose awakening (and thanks to Noel and Serah's interference in AF300 and reappearance in AF400) leads it to deem all life form dangerous to its survival. Adam manages to create a time loop where it will send itself in time back to when it is activated, kill Hope and Alyssa, and create a world with Replicas and live out its existence in peace.
With that event resolved, Hope realises that a new ark has to be constructed instead, thus putting himself into cold sleep and awakening in AF400 (along with Alyssa) in order to meet Noel and Serah (as foretold) and decide on their future path. With the aid of Graviton Cores scattered throughout time (I don't understand this point either, chalk it up to gameplay I guess) he is able to create a new Cocoon, which will be operational just before the breaking point of the crystal pillar.
Thus he goes to sleep again (Alyssa cannot be found after Serah and Noel attempt to go into the future at the end of Episode 4) and wakes up in time to help the two out in their final battle against Caius.
Snow -> Goes off to find Lightning at the behast of Serah. Also gets caught in a Paradoxical time trap, and is tasked to protect the Pillar from a giant Tomato Pudding because many more normal ones are being summoned to attack the pillar. Realising that he alone is unable to do much, he employs the use of a L'cie mark (how? with whom? Fragments only explain that he managed to get one) to keep himself alive longer, until Serah comes along to help.
Once that situation is resolved, he is sent back to where he came from. Does not appear again in the story.
Serah -> She, too, is given the power of the Sight. Early on it's not fully developed, thus she gets glimpses of the future from time to time, without knowing the eventual consequence (she learns of it, together with Noel, by Episode 5). Eventually they save the future by stopping Caius and his crazy plan to kill off everyone in order to force the gate open, but at the very end of the game her Vision fully develops and she sees a future that is not told to us, and dies.
Noel -> Starts off wanting to go to Vallaha in order to get to Etro and get his point across. Slowly gets caught up in Serah's grand ideal of saving the future, in turn saving Vanille and Fang, and returning to Vallaha to find Lightning. Initially does not understand the meanings of all the Yuels (neither do we) but in Episode 5, while living in the forced Dream world, he finds out the terrible truth.
However, unlike Caius, he sees his Yuel die, but with a smile on her face, knowing that she'll see him again. He realises that she has accepted her fate, but all the while wanting to be reborn again and again because she wants to be with her Protector again. Armed with this knowledge, he faces Caius for the final time, telling him what Yuel's true intentions were.
By the end of the game, we see Caius stab himself through the Heart, thus dying, and removing the presence of Etro in the process. Of course, we are only told of this in the ending, after Serah's vision, and that Chaos from Vallaha has flowed into the real world, merging both worlds together in a Timeless zone.
Technically, Caius won.
To be continued.....
Edit
