So did they ever actually explain what astrals are?

It makes sense in the early setting, but the more details they came up with along the way the less sense it made
>Humans, primals, no being can achieve space travel in this setting aside from moon dwellers. Even Zooey cannot travel to space (Therefore Astrals did not come from another planet)
>The story goes out of the way to say the planet(whatever the planet is called) is the only place that exists within this setting, nothing exists outside of the planet.
>Even universal rewriting deities in this setting are far more limited than they seem at first, the setting is inherently more limited than it seems early on. As the recent event shows Qilin killing literally everyone including Bahamut and the angels somehow
>The otherworlders are the original dwellers of the planet before it went to shit randomly(I don't know if they ever explained what happened that made people just randomly die off or start mutating into monsters). So Astrals are not the original dwellers of the world at all, both skydwellers and otherworlders predate them

So where did they come from, and where did they fuck off to after the war? There is no Astral world really.