Fell Xenologue *Spoiler* discussion

In particular I want to know what happened? How did everyone die? How did they all become corrupted? What happened to Veyle? Alear from this world only had blue hair, was she/he 100% divine dragon?

My hot take is that this is one of those examples where the backstory and world building in more interesting than the story itself.

Based entirely on little clues and subtext I have some ideas about what happened to the fell world but I am curious what you all think.