Erikia being captured in a crystal soul by the Vahnatai after A3 would have been an awesome twist!
Perhaps A5 will include one of the two ends of the ZKR, to help give it a real place in the world.
Btw, one of the problems with mentally understanding Avernum is that, really, there can be many, many layers. It's hard to visualise how these all fit above and below each other.