Long rambling post about The Locked Tomb below - beware, spoilers ahead for the whole damn thing.
So I haven't seen anyone talking about something I noticed in my reread of The Locked Tomb books, more specifically in HtN, and that's the usage of the skull icons at the beginning of chapters:
Now, I'm sure it's no secret to anyone at this point that in GtN these are typically indicative of who or where is important or prominent in that particular chapter (ie. the First House skull for the candidates' arrival to the First, the Sixth House skull for when Pal and Cam are first introduced, etc), or to foreshadow events within the chapter (ie. the Firth and Fourth House skulls on the chapters containing their deaths).
Tasmuir continues this usage of the skulls into HtN, but adds another layer to it by having broken or cracked variants of the skulls in play as well:
On first read, they didn't really click for me, but looking at it again with the knowledge of Harrow's lobotomy, it makes perfect sense as these particular skulls only show up on chapters that contain falsehoods or take place within the bubble version of Canaan House.
Any time the skull at the top of a chapter is broken, you can be almost entirely certain that, somewhere within it (or sometimes even the entirety of it), there will be a lie concocted by Harrow's false memories.
Interestingly, as far as I've been able to find, the only chapter in the past and what should be distorted memories where Harrowhark is addressed as "Harrowhark" in the narration (ie. not narrated by Gideon) that has an unbroken skull is chapter 3. This tells me that, despite the fact that the memories have of course still had Gideon Ctlr+Alt+Deleted from them, the information we get is likely still more or less the truth.
And that's not all, cause Tasmuir continues the icon-at-the-start-of-chapters trick into NtN too, but here it's much more broad in terms of what you'll find. HtN introduced the bug heads for the chapters talking about the attack on the Mithraeum, but NtN throws a load more into the mix too.
These two are fairly obvious in terms of their usage: the cracked Sixth House skull is used when Paul happens, and the Gideon specific Ninth when Kiriona is revealed.
There's also a pair of icons depicting the Tomb, one locked and one not, that are also fairly self explanatory in terms of their usage on Nona specific chapters before and after the Tomb is opened.
However, there are a couple that are a little more interesting, mainly insofar as they are only used the once:
The tree makes sense, it's likely the Tree of Knowledge from the Garden of Eden to go with the name of the BoE as it's used when they're first mentioned, but it's the plant/leaf that's stumping me as it's from chapter 17 where we get to listen in on CamPal being soft for each other the morning after Pyrrha goes missing, Nona and the kids have their last day in school together, and we get a bit more lore about the Angel. Not sure yet how the symbolism works on this one, but I'm working on it.
Then there are only other two icons of note:
The tower one is fairly easy as it pertains to some of the chapters where the Tower Princes are mentioned or involved (and I have a WHOLE load more ideas about them that will not fit in this already far too long post). The broken Second House skull I'm not 100% on, but my assumption is, based on the fact that it's used on chapter 10, that it's to do with the presumably Second House barracks being taken over. Though don't quote me on that one as it's also where Pyrrha gets injured so hell if I know.
In any case, TLDR: Tamsyn Muir you have put altogether too much thought into the iconography of the joddamned chapters and I love you for it.