W is for—War
I'm no Harry Turtledove, so the minute I realized that pretty much the entirety of A Tree of Bones was going to take place during all full-on clash between Hex City and the forces surrounding it (hexacious, as well as non-), I knew I was at least partially boned. So I opted for both a flash-forward which would skip a fair amount of build-up and establishment—a bit of an HBO's Game of Thrones model which would jump my characters right into the battle (or string of battles), ensuring I could hit the ground running with my tools already assembled—and a certain timeline compaction which would force me to keep bulling on through, finishing things up with a spatter of plot twists and a multi-part climax. While A Book of Tongues takes place over roughly two years, folding back and forth through time throughout, A Rope of Thorns takes place sequentially over roughly a month, and A Tree's action is the shortest yet—four days at the most, barring an epilogue.
X is for—Xenogenesis
In case you haven't noticed, “X” words are pretty damn hard, both to find and to define. But since we've already established that hexation has a genetic component (which is how the Chinese maintain their breeding-for-hexation program, one assumes, as well as the main reason it's generally considered a bad idea for hexes to hook up with each other), and because this one means “the supposed generation of offspring completely and permanently different from the parent”, I'm going to use it as my opportunity to talk about the problem of hexacious kids, in general.
At the start of A Book of Tongues, Doc Asbury tells Ed Morrow and a bunch of other agents that most hexes “express” either at puberty (if female) or after suffering life-threatening injuries (if male). So you might think that there are very few hexes who express as children...except, of course, for the fact that our story is set during a time-perid when infant mortality was crazily high. One can't help but think that there must be a fair portion of people who express as children, or even as infants. Most of them probably don't make it to adulthood, because either they're killed by the non-hexacious around them once their power is recognized, or because other—older—hexes suck them dry, sometimes even their own parents, sometimes without even knowing they're doing it. Mrs Followell admits as much, in her brief back-story.
With these possibilities always looming, it makes sense that much more of A Tree than you might think is predicated on the idea that the Hex City Oath may make it possible for hexacious and non-hexacious parents of hex-babies alike to deal with their dangerously unpredctable offspring in a slightly more humane way—to bond together in a literal way, facing the future as a unit, nurturing, tutoring and supporting each other. And given that (as Asbury also observes) much of the general misery hexes have inflicted in the past springs from their sense of themselves as spiritual lepers feared and hated wherever they go, forever aloooone, this may bode well for human/hex relations in future...once this current war is put to bed, that is.
Tomorrow: Our alphabetized tour of the Hexslinger-'verse concludes, with Y and Z!