I need an ending explanation (SPOILERS, obviously)

[AXBNBS]

So, I finished the game yesterday and I think I barely understood anything that happens after you beat Orphan's first phase. Got lots of questions: why do they kill Orphan in the first place? I think they're pretty aware at this point that, if they do, they will destroy Cocoon. Why does Coocoon get destroyed after defeating him? Shouldn't they become Ragnarok first and then destroy it? How does the "turn into Ragnarok" thing exactly work? How did Fang become Ragnarok in the past without killing Orphan? Why is Fang's mark different to the ones the rest of the characters have? Why do the other character marks change? Why does Fang try to hurt Vanille at one point? Where were the other characters and why were they having that strange future visions when Orphan tried to fool Fang and Vanille making them think they had become Cie'th? How do Serah, Dajh, Lightning, Snow, Hope and Sazh get back from the cristal dream? How did Fang and Vanille crystalize in that specific way? How did they become cristal in the past if they didn't manage to destroy Cocoon? How did both of them managed to turn into Ragnarok? Does this game's ending make any sense at all?

[Razor<<Clawson>>]

Well it was their Focus to kill Orphan. For further info on the part about Fang you can check out her profile at Final fantasy wikia. As for them turning into crystal "that" way... because logo, art by Yoshitaka Amano

[AXBNBS]

Of course it was their focus, but I thought they wanted to save Cocoon no matter what, so they refused completing it, right? It still doesn't make sense for them to crystalize that way, it's completely different from the way Serah and Dajh crystalized when their completed their focuses. How the hell would they know they would turn into crystal in that specific way, creating a giant pilar that would stop Cocoon from falling?

[Unseen]

Originally posted by AXBNBS:

Of course it was their focus, but I thought they wanted to save Cocoon no matter what, so they refused completing it, right? It still doesn't make sense for them to crystalize that way, it's completely different from the way Serah and Dajh crystalized when their completed their focuses. How the hell would they know they would turn into crystal in that specific way, creating a giant pilar that would stop Cocoon from falling?

Well you remember when they all turned into ceith, but suddenly changed back.

There was no coming back from that, for normal people... It was a miracle. Not sure how FF13's world works, but I assume some kind of holy power was looking out for them.
That's just what I think, I cant say why they crystalized like that other than they willed it to happen like that. And cocoon did get saved just not in the way they'd thought. I believe they killed orphan because they felt they had little choice the way everything was going.

Mainly cuz orphan seemed just as sinister, if orphan had been a kind falcie who wanted help I doubt they would of attacked it the way they did.

You notice when they turned back from ceith they explained that it was cuz of hope, not the character lol, but the hopeful spark they had because of the love and friendship they had for each other. Basically a miracle.

[Toph]

Basically, mattshaneworkman is correct. It is a miracle. They are saved and empowered by the Goddess, Etro, and it's suggested they were given a new "Focus," hence the white brand. They no longer rely on the power granted by a fal'Cie--the same power that also binds them to their original fate.

Also, this is not the first time Etro intervenes within the game itself.

Here are a couple excerpt of lore from the FFXIII datalogs:

Ragnarok took wing; made to smite Cocoon, and thereby deliver us our everlasting peace. But Her Providence would not let it be.
The Goddess pitied the fools who so blindly bowed to Lindzei's will, and so She robbed Ragnarok of power, putting the l'Cie to an early crystal sleep, Focus yet incomplete.
-- Sermons of the seeress Paddra Nsu-Yeul

This refers to the first time both Fang and Vanille failed to destroy Cocoon during the War of Transgression--which takes places around 600-700 years before the events of FFXIII. While Fang eventually gives in to her Focus, Vanille refuses. This causes Fang to create an incomplete Ragnarok, which scars Cocoon in the chaos, but ultimately fails at destroying it.

However, both Fang and Vanille are saved, and put into crystal hibernation, by Etro.

Her Providence sought nothing.
Her Providence made nothing.
She but looked on, silent in Her sorrow.
The Goddess pitied mortals, destined as they were to die, and so She deigned to intervene in the hour of their greatest peril. She averted cataclysm that was to be, and put to rest the ones who would have robbed so many of what time fate had ordained.
Her compassion did not end at this.
The Goddess pitied also those subjected to that fate of Focus, crueler still than death. To them She sent Her messengers, to deliver hope when all was lost.
-- Sermons of the seeress Paddra Nsu-Yeul

So, this particular excerpt is literally a reference to the Eidolons. Eidolons are a manifestation of Etro's benevolence and pity for those who are I'Cie--essentially people being controlled by fal'Cie--and another means to encourage them to fight against their fate.

Now for some of your more specific questions:

why do they kill Orphan in the first place? I think they're pretty aware at this point that, if they do, they will destroy Cocoon.

Well, their choices are a bit limited. They could have chosen to hide on Gran Pulse and runaway from their Focus, but they would have turned into mindless cie'th in the end. Instead, they chose to face their fate head-on and fight; not to destroy Cocoon, but to save it. Even if they had no idea how to do that nor the time to spare to really figure it out(again, their brand will turn them into Cie'th). They were esssentially walking into a hopeless battle, determined to win and hoping for the best.

Why does Coocoon get destroyed after defeating him? Shouldn't they become Ragnarok first and then destroy it? How does the "turn into Ragnarok" thing exactly work? How did Fang become Ragnarok in the past without killing Orphan? Why is Fang's mark different to the ones the rest of the characters have?

Ragnarok is a powerful transformation that was given to both Fang and Vanille by the Pulse fal'Cie, Anima, to destroy Cocoon during the events of the War of Transgressions.

As I explained previously, Fang attempts the transformation but it's incomplete. Furthermore, Etro intervenes. Cocoon is damaged, but not destroyed. Fang and Vanille hibernate as crystals until the events of FFXIII.

Why do the other character marks change? Why does Fang try to hurt Vanille at one point? Where were the other characters and why were they having that strange future visions when Orphan tried to fool Fang and Vanille making them think they had become Cie'th

As I explained before, the brands changing can be interperted as Etro's intervention. A lot of that scene is also implied to be Orphan's using illusions along with torture to force Fang and Vanille to transform into Ragnarok.

The strange visions, however, are the new "Focus" they have recieved now under Etro's influence.

Fang attacking Vanille, and the others, is just her attempt to stop anyone from getting in her way of doing what she thinks must be done--transforming into Ragnarok again and destroying Orphan/Cocoon. However, again, the transformation is incomplete without Vanille and she fails once more.

How do Serah, Dajh, Lightning, Snow, Hope and Sazh get back from the cristal dream? How did Fang and Vanille crystalize in that specific way? How did they become cristal in the past if they didn't manage to destroy Cocoon?

Again, all Etro.

Does this game's ending make any sense at all?

It does, actually. I barely touched all of the datalogs during my original play through and the story felt comprehensible and complete, imo--though I still had questions much like you. So, I eventually went back and gave those datalogs a browse.

Also, a lot of this lore gets fleshed out even further in the sequels.

[Toph]

I typed way too much already, but I think it's also worth pointing out more one thing. The source of those datalogs entries I quoted, Paddra Nsu-Yeul, is actually a pivotal character in sequels.

It's really cool to see how small, but interesting, references like these end up coming full cycle in the end.

[tiornys]

I'd like to add two things to the above. First, while Fang as Ragnarok didn't destroy Barty/Orphan, she did destroy the protective barrier around it. That's why it was vulnerable to the party's attacks when they came back from being Cie'th.

Second, it's true that they were basically making a leap of faith when they decided to kill Orphan, assuming that they would somehow find a way to save Cocoon without knowing what that way might be. However, it can be argued that it's actually quite rational to make a leap of faith at that point since the party had just experienced a literal miracle. They had the benefit of knowing that god (or at least a god) was backing them up.

[Toph]

Originally posted by tiornys:

Second, it's true that they were basically making a leap of faith when they decided to kill Orphan, assuming that they would somehow find a way to save Cocoon without knowing what that way might be. However, it can be argued that it's actually quite rational to make a leap of faith at that point since the party had just experienced a literal miracle. They had the benefit of knowing that god (or at least a god) was backing them up.

Oh, yeah. Excellent point.

My speculation was generalized in regard to them choosing to return to Cocoon as a whole. But I agree completely. Even if they didn't fully understand who had helped them or why, Etro made her support fairly clear to them all.

Them choosing to to take Orphan down at that point wasn't unreasonable at all.

[AXBNBS]

So they needed to turn into Ragnarok in order to destroy Orphan, not Cocoon? The way I understood it, I tought they had to destroy Orphan to gain the power to turn into Ragnarok and destroy Cocoon, or something like that. Still, how's Fang able (being an incomplete Ragnarok and all) to destroy the barrier around Orphan? Also, I'm still not sure I understand why Fang's mark is different to the ones the rest of the characters have. Wouldn't it make more sense if both Fang and Vanille's marks where different?

[Toph]

Originally posted by AXBNBS:

So they needed to turn into Ragnarok in order to destroy Orphan, not Cocoon?

Orphan is a fal'Cie and also the source of Cocoon's power. Destroying either is essentially the same thing.

Here's relevant datalog in regard to Orphan from in-game:

This mysterious being fuels the fal'Cie Eden with the power necessary to maintain Cocoon's complex operational systems, and as such, its death would bring about Cocoon's certain destruction. Nevertheless, its death is what Barthandelus desires, for he seeks to offer the lives of the world’s millions of inhabitants in sacrifice to call the vanished Maker back to this realm.
As Sanctum fal'Cie and l'Cie are themselves incapable of harming Orphan, Barthandelus requires the assistance of Pulse l'Cie. If they can transform into Ragnarok and destroy Orphan, Cocoon's demise will be assured.

Originally posted by AXBNBS:

The way I understood it, I tought they had to destroy Orphan to gain the power to turn into Ragnarok and destroy Cocoon, or something like that. Still, how's Fang able (being an incomplete Ragnarok and all) to destroy the barrier around Orphan?

No, Fang and Vanille are given the power to transform into Ragnarok specifically so they can accomplish their Focus of destroying Cocoon. As you clearly see through playing the game, it's not exactly easy to destroy fal'Cie, hence they specifically were given a powerful transformation to insure they could accomplish their goal.

And an incomplete Ragnarok still being capable of destroying Orphan's shield is likely just a testament to the transformations true power when actually complete. Like I said, fal'Cie are very powerful. In contrast, Ragnarok would have be even stronger if the fal'Cie put so much faith in Fang and Vanille being capable of destroying Cocoon while utlizing it.

Originally posted by AXBNBS:

Also, I'm still not sure I understand why Fang's mark is different to the ones the rest of the characters have. Wouldn't it make more sense if both Fang and Vanille's marks where different?

Well, it's hinted Fang's brand is different because she losts her memories and, therefore,
lost her Focus. Vanille pretends like she lots her memories as well, but we learn that's not actually the case. Also, you could consider Etro's interference when Fang originally attempted to destroy Cocoon during the War of Transgressions.

It's likely a combination of both of these things that leads to Fang's brand being different from the others.

[Unseen]

One thing I was wondering tho, how did Dahj and Serah come out of crystal stasis? Was it because the heros protected cocoon, or was it cuz the falcie had lost their power?

Or was it another miracle?

[Odinsknight101]

Originally posted by mattshaneworkman:

One thing I was wondering tho, how did Dahj and Serah come out of crystal stasis? Was it because the heros protected cocoon, or was it cuz the falcie had lost their power?

Or was it another miracle?

Explained in 13-2

[WickedRequiem]

Just for 13, it comes down to this.

Orphan got tired of being humanity's slave and wanted to die.
Orphan, however, could not directly commit suicide due to his nature.
Thus, he put into a motion a plan to get assassinated by "heroes".

Entire XIII was a giant roundabout way of committing suicide by Orphan.

[AXBNBS]

Okay, guess that in the end it all makes much more sense than I thought. I still don't like that the game relies so much on datalogs, instead of explaining things directly to the player. I thought that people were exagerating in the begginning, saying that the game was too hard to understand unless you cared about the inmense in-game Wikipedia, but looks like I was wrong in the end...

Anyways, thanks everyone (specially Toph) for helping me understand this mess xD