As is traditional so far, I give warning that I've only read this chapter and not previous ones. Please bear with me, this might get long as I describe where I'm talking about things.
One of the main things I noticed when reading was about the sentence construction. For one, there are a lot of "was <verb>ing" and "were <verbing>" sentences. These can almost always be replaced with <verb>ed. For example, "Onmk's senses were still reeling" could be "Onmk's senses still reeled". (This may not be the best place to change, but it is an early example of what could be changed.) Changing these often makes the text quicker to read, both in a slightly more straightforward way to interpret the sentence and in the fact that it reduces the number of words to read.
This may be because I haven't read the previous chapters, but I was quite lost in Onmk and Ciera's relationship. Early references to Memories hint that I'm missing something. However, at various times he acts like he knows her completely (she always felt belittled by her short stature, these days she wore her hair..., she was always difficult, strong-arming her always worked well, a friend of fifteen years), and at others like he barely knows her at all (looks at her face "like for the first time", she tells him her age, he tries to manipulate her as if he has barely any idea what she's like, he doesn't appear to know about Ciera's adversarial relationship with Denalia).
Is this is third-person limited? There are a couple of places where, despite being in Onmk's viewpoint, we get information about what others are feeling (Ciera always felt belittled by her height, Ciera looked at him amazed, Denalia looks eighty years old but is stated to be sixty). They aren't major, but they did stand out to me.
Ciera's description included a twinkle of "malicious" light when she thought. First of all, this means she's mean when she thinks? Second, at the end of the chapter her eyes start to twinkle when Denalia is picking on her. Was this supposed to be her thinking evil thoughts about Denalia?
There are places where things are repeated or alluded to that seem redundant. Some examples are Ciera putting dangling wisps of hair back behind her ears "each time they got back before her eyes", Onmk telling Ciera she doesn't know these women when describing them to her, and a number of the dialog attributions. The dialog attributions are especially true when the dialog is in a paragraph that the speaker does some other action as well.
There are places where much is just stated generally instead of given in details. Examples are Onmk thinking Ciera is always difficult and needed to be argued into doing anything, Onmk not being able to tell her she couldn't read the Compendium pages yet (although that might have been done in earlier chapters), and "something" passing over Ciera's face when she talks about the lead documentalist.
I like that there's a time limit -- only a couple of days at most. However, right after that Onmk gives Ciera a hint to trying to read the book: that it's in a cipher. If she feels compelled to try and read the book, two days is no time at all to try to decode a cipher. Even if that was all you were doing. Right after this, Ciera decides to investigate it more tomorrow morning, so they're already losing up to one day there. It doesn't seem like the two day time limit is very pressing on him.
When Onmk is deciding he needs Ciera's trust, he doesn't want to contemplate the consequences of failure. The readers, however, do want to know what's at stake, or at least some potential downside. If you covered that in earlier chapters, great. Otherwise, here might be a good time for it.
A few of sentences didn't make sense to me. One was Onmk with the books, especially "Turning his gaze inside...". That part was the confusing portion of that sentence. The second was Denalia asking of Ciera "What did you do? Stamp them over to..." The third was near the end of the chapter, when Ciera says "Can you stop this, please?" I didn't have any idea what Onmk was supposed to be stopping. Especially since she goes on to talk about hitting Denalia.
Does Ciera's constant chatter cause Onmk to be depressed? At the beginning of the last section, despite her chatter, he felt confident. In that same paragraph, it seems like a very tenuous plan -- make Ciera happy so she's more amenable to his arguments -- but that may be just in line with Onmk's character.