A quick TL;DR counter theory as to the story of Gravity Rush (SPOILERS APLENTY)

Very Quick TL;DR:
Inception + Black Hole Time Dilation + Yggdrasil Being Eaten + Dreamer's Traumatized and/or Comatose and/or Dying = They're all going to eventually die.
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Made on 18/03/2012 due to recent games
We need a reclassification: DLC is Downloadable Content. DUK is Downloadable Unlock Key for locked on disc content.

Less Quick TL;DR:
(In case...)

GR's reality is a Dream. Cyanea's the Dreamer. The Dreamer's may be Comatose and/or Dying Nevi's want to destroy the dream. D'nelica was just an idiot. Aldreaux was his source of knowledge on Nevis.

Kat was a queen, possible creator. She's now a shmexy shifter. Dusty isn't a Nevi but is similar.

Alias is just weird. Nala's on top. Singlor's down low. There are multiple dreams. Gade's a door.
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Made on 18/03/2012 due to recent games
We need a reclassification: DLC is Downloadable Content. DUK is Downloadable Unlock Key for locked on disc content.

TL;DR format of multiple walls of texts:
(Trust me. This single wall of text is compact compared to roughly 6-8 walls of texts)

The world is basically in a state of inception of sort, the bottom represents a black hole, time dilation is in effect, bottom is slower, top is closer to normal time.

Kat was an important fictional dream character with responsibilities, possibly a creator, creators who are possibly subconsciously aware dream entities within the dream of the dreamer.

The Dreamer, most likely Cyanea dreaming herself in this world, while she sometimes dreams within her dream, is either sleeping normally, having nightmares, escaping harsh reality in her dreams, is comatose and/or is dying.

D'nelica knows more about Nevis thanks to Aldreaux but ultimately is just another typical bad guy who thought he could use the powers of Nevis which got out of control. Nevis who are ultimately forces to destroy the world and the dream.

Dusty and Raven's Crow are Nevi like, but lack a core. They are also forces for good, though Alias seems to have a connection with Nevi and Kat. Or Alias can partially control Dusty since he can control Nevis.

There are multiple worlds, either multiple realities or multiple dreams. Nala is demonstrating the top effect, and is harder to reach much like Kat's memories, while Singlor demonstrates the lower effects.

End Theory being, they're in a Dream world of a being who is sickened in some way, and the Dream is undergoing a self destruction of sort, either from waking up, from naturally dying, or succumbing to psychological or emotional trauma. Kat is fixing up the dreamer's memories much like her own as she gave up prior to being who she is now. But the ultimate truth is that the Dreamer will wake up, and the Dreamer itself being what shaped the gods, will also ultimately die. The world of Gravity Rush is basically one fated to perish.

Now excuse me. I'm going to go grab a beer.
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Made on 18/03/2012 due to recent games
We need a reclassification: DLC is Downloadable Content. DUK is Downloadable Unlock Key for locked on disc content.

Freaking Tidus, ultimately replaceable and useless.

Though yeah. Yu Yevon is another TL;DR plausible theory.
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Made on 18/03/2012 due to recent games
We need a reclassification: DLC is Downloadable Content. DUK is Downloadable Unlock Key for locked on disc content.