So about that Eden

[Lium]

The reason for going outside the Empty is...

It was explained that in order to summon the correct aspected primal they had to be in the right region with the appropriate element, i.e. a rocky/mountainous region to summon Titan.

Then, hopefully, after the primal was defeated, its aether will go back into the land and rejuvenate it. So, the mountains and the land around Titan changed back to brown and normal looking after he was slain. It will then spread from there to other parts of the Empty.

If you remember, after we defeated Leviathan, only the immediate area around Eden was affected.

[LineageRazor]

The reason for going outside the Empty is...

I think the confusion is coming from the point that

the mountains and land around Titan are brown and normal looking BEFORE he is slain. The battlefield doesn't look as though it's in the Empty at all. I was totally on board with the idea that we needed to perform the summoning in areas where that particular element was dominant, but the implication was that the place we were going was INSIDE of the Empty. In the case of Leviathan, a place where water existed in great abundance before the Flood (but was dry, white, and inert, now). So, why are there brown, rocky cliffs and a flowing river during the battle with Leviathan, instead of a featureless white basin?

It seems as though we've gone back to Norvrandt to fight these Primals, which makes no sense given the dialogue leading up to the fights. I mean, it makes sense from a gameplay perspective; a raging river or craggy backdrop makes for a much more engaging setting than white nothingness, but it doesn't track well with the plotline.

Either we're not fighting in the Empty, or the Empty doesn't look Empty for some reason. Perhaps the Primal influenced the setting with its magic? Shinryu seemed to be able to construct its own battlefield, after all.