If you haven't finished Azteca yet, then SPOILERS!
If you have, you know that the music changes to the Post-Apocalyptic theme and much of the setting and atmosphere changes. Also, meteors falls from the sky and crash into the ground in random places.
Simply put, I hate this. I know the developers put it in for the sad effects, but it's overstimulating, and the music is annoying (and all the same, pretty much everywhere). Now that I've finished Azteca (I'm in Empyrea right now), I never want to go back but whenever I have to in order to finish I side quest or something it annoys me so much.
My suggestion is that Kingsisle has an option in Settings or Advanced Settings or whatever so that after you have finished Azteca, you can choose between the Post-apocalyptic horror theme and meteors, and the normal version. This would make the game so much more fun for me and I wouldn't have so many Azteca side quests clogging up my Quests section of my spellbook anymore.