I know it's an old thread but, just now getting to read the book.  I'm not done with it yet.  It seems to me like this book isn't its own parallel universe.  It seems to me that this is post apocalyptic Alera.  It was alluded to in the final Alera book that it would take the queen in the Canine territory about a century or so to reproduce enough for an invasion.  In that time Tavi or a descendant would have made plans for the future.  Most likely building up towards the skies made the most sense and maybe, the spiders couldn't live at such altitudes until recently. Perhaps the queen evolved or her offspring evolved to tolerate the altitude and light. Their technology and  the way of harvesting powers would change too, if the spiders ended up taking over their world.  Yes I know there is still soil but that's not to mean there isn't also croach.  I'm hoping they'll do an expedition to the ground.  Find ruins of Ancient Alera...The Builders.  As I recall Tavi had a mind for architecture and other means to build something that will last without powers or magic.  I'm also wondering if Ferus is actually Fidelias somehow. I'm guessing that the queen (I'm referring to Cavendish) is the one from the Canine country as she seemed the next, most human.  Or more, she longed to feel a bit human because she displayed jealousy at her mother's "flaws".  Plus she's stickler for manners which the original queen was as well. To feel more human.  It seems to me that the cats and her servant were just taken and replaced as before. Just saying, it seems like a possible theory.  Thanks for letting me ramble.