The arches and symbols are a series of arches and symbols at the beginnings of chapters. They rotate and change for every chapter. What they mean should be intuitively obvious to the casual observer, as Robert Jordan used to say.
I decided to use them because I wanted to have interesting things at the start of each chapter. These were done by Isaac Stewart. I originally sat down with Isaac and said, “I want to be able to build symbols at the beginning of my chapters. Something like in The Wheel of Time, which I really like, but I don’t want to imitate them, I want to go somewhere different. I want to have different pieces that interlock together that form some stonework symbol that’s at the beginning of every chapter.” I also told him what I wanted the symbols to mean (among other things) and he actually transmogrified all that into an archway. I had originally been planning it to be some sort of inscribed rock stamp or something like a little relief at the beginning of each chapter, but he persuaded me that an archway with a different kind of symbol in the center would be better. So, they became arches through Isaac’s working with the art and changing things and deciding what would look good visually.