This thread will contains spoilers for:
Final Fantasy XIII, Final Fantasy XIII-2, Final Fantasy Type-0, and Final Fantasy Versus XIII.
Proceed with caution -- you have been warned.
Before you start -- this video is required.
This is the Fabula Nova Crystallis lore foundation, written by Kazushige Nojima.
So, to kick things off, here's a theory I've been kicking around in my head. Feel free to discuss/add/go off on tangents etc.
Spoiler Show15|19:54 - <Shamdeo> hehe
15|20:07 - <Shamdeo> Ready to hear my theory? XD
15|20:07 - <Kagari> sure
15|20:08 - <Shamdeo> So, a huge huge part of the Fabula Nova Crystallis lore states that...
15|20:08 - <Shamdeo> There is the world of the visible
15|20:09 - <Shamdeo> And the world of the invisible.
15|20:09 - <Kagari> right
15|20:09 - <Shamdeo> Valhalla is in the world of the invisible, and is often referred to or generally implied to be in another plane than Pulse.
15|20:10 - <Shamdeo> However... it's also stated that if the balance of the visible and invisible worlds is broken, everything is destroyed.
15|20:10 - <Kagari> ;o
15|20:10 - <Shamdeo> In this ending...
15|20:10 - <Shamdeo> Pulse... and the world of the visible...
15|20:10 - <Shamdeo> Becomes the world of the invisible and the new Valhalla.
15|20:10 - <Shamdeo> Along with Etro to occupy it.
15|20:11 - <Shamdeo> This means that the world that was once invisible... is now visible.
15|20:11 - <Shamdeo> With Etro being featured prominently.
15|20:11 - <Shamdeo> Can you guess what game this might be?
15|20:11 - <Kagari> bearsauce
15|20:11 - <Shamdeo> Indeed.
15|20:11 - <Kagari> ;oooooooooooooooooo
15|20:12 - <Shamdeo> Versus meaning: against, turned, change, overthrow and destroy.
15|20:12 - <Shamdeo>
15|20:12 - <Shamdeo> What if... the change between the visible and the invisible world was a cycle?
15|20:12 - <Kagari> My mind will be blown
15|20:13 - <Shamdeo> hahahaha
15|20:14 - <Shamdeo> Maybe Agito was part of that cycle.
15|20:14 - <Kagari> hmmm
15|20:14 - <Kagari> I wonder
15|20:14 - <Kagari> Was it said if the secret ending was canon in that game
15|20:14 - <Kagari> or what
15|20:15 - <Shamdeo> For Type-0?
15|20:15 - <Kagari> yeah
15|20:16 - <Shamdeo> I know that happens in another cycle of the world, and since Arecia Al-Rashia removes the crystals, that ending happened.
15|20:16 - <Shamdeo> I want to know what role Diva serves.
15|20:16 - <Kagari> she's maaya sakamoto
15|20:16 - <Shamdeo> hahaha
15|20:16 - <Shamdeo> yes
15|20:17 - <Shamdeo> Though Type-0 is ongoing.
15|20:17 - <Shamdeo> So they might hold off on that.
15|20:17 - <Shamdeo> On the big connection.
15|20:18 - <Shamdeo> Though I think Diva has something to do with Agito's -cycle-.
15|20:18 - <Kagari> I would imagine
15|20:19 - <Shamdeo> Though Arecia... is very strange.
15|20:19 - <Kagari> She is
15|20:20 - <Shamdeo> She was able to uncrystallize Machina and Rem...
15|20:20 - <Shamdeo> I don't want to call her a fal'Cie.
15|20:21 - <Shamdeo> Because she would be limited to the world, and she is apparently outside of the cycle.
15|20:22 - <Shamdeo> This idea of a same world caught in a cycle might explain some of the same terminology of l'Cie and fal'Cie.
15|20:23 - <Kagari> I thought the twist on her character was a bit crazy
15|20:23 - <Kagari> lol
15|20:23 - <Shamdeo> Yeah it's definitely strange.
15|20:24 - <Shamdeo> Though... a thought kind of occured to me.
15|20:25 - <Shamdeo> Humanity was born from Etro's blood, and she gave them chaos/heart.
15|20:25 - <Shamdeo> Etro has a connection to humanity in a way, being her creation.
15|20:25 - <Shamdeo> It's the same kind of feeling I get when I see Arecia "meddling" with humanity and the crystals.
15|20:26 - <Shamdeo> Etro and Arecia are both outside the -cycles-.
15|20:27 - <Kagari> ;x
15|20:27 - <Kagari> Nojima needs to write a novel on all this
15|20:27 - <Shamdeo> Though I'll have to do more research on that part.
15|20:27 - <Shamdeo> I need to know more about her.
15|20:28 - <Shamdeo> If Lindzei was able to destroy the world... that would make sense about the geography changes.
15|20:28 - <Shamdeo> -Lindzei is said to have destroyed everything on Gran Pulse. It is said that Lindzei tore down the mountains, razed the fertile land, ate the fruits of the earth, pulled up the river and cast it down, washing away the people and creatures of the land.-
15|20:28 - <Shamdeo> This is what happens at the end of XIII-2 I think.
15|20:29 - <Kagari> Looks like it anyway
15|20:29 - <Shamdeo> hahahaha
15|20:29 - <Shamdeo> what if the true ending
15|20:29 - <Shamdeo> is this but longer and implies versus is next
15|20:30 - <Shamdeo> or it could be a happy ending and totally bonk over my theory
15|20:30 - <Shamdeo> lol
15|20:31 - <Kagari> It'll be interesting to see