I was thinking about the importance of the Moon in the game, implied by 2 pieces of unused content but also in the credits of main game and Comrades; as we know, the unused descriptions of Chapter 13 and 14 reads as
"Immediately after Noctis was pulled into the Crystal, he was confined and/or imprisoned within an odd space."
All of the Phantom Swords (Royal Arms) collected thus far are scattered around.
Noctis isn't aware of the situation of the Imperial capital, or of his friends."
"Angelgard, so strongly protected that none may enter, not even Ardyn. Noctis continues to wait collecting moonlight for the Ring, earnestly hoping for the safety of both his friends, and the world."
When the moon has all but disappeared, an exit appears within the prison, and he hears the voice of a god that says "The time has come". By the time Noctis has gotten all of the power of the star, and has left the prison finally, ten years have passed within the world.
it seems to me this side of the plot was "removed" to make things easier to understand, but it still seems to be present.
World of Ruin was only totally covered by darkness during the end of the 10 years, but the moon was still there and visible for the most part.
"And the moon is the only light we'll see"
the Nidus poisoning the planet
so what happens then? as time passes, the moon and sky begins to turn red and monsters go rampant, this only lasted for a period of time.
and then the last ray of light, at this point the ring is full; the ring was charged entirely by the light literally coming from the moon.
I would say Noctis remained in prison sleeping during all this time; anyway, just some thoughts I wanted to share, unfortunately the game only provides fragments that implies a certain explanation but it doesnt outright explains it (the problem of the lack of story exposition, once again).
I see, well I dont know all the details but you can see more of his documentation here >
https://www.lucianociccariello.com/research/finalfantasyxv