Here we see the introduction of the book Serinth keeps in her library called "Heyoke the Wolf".

Jagex is talking to her in her library and sees it, covered in glass. He asks if that's what he thinks it is and goes up to it. He gets into an argument with her, saying it's the most sought-after book from Rosewater, maybe in all of history, and she has it in a fucking glass case?

She explains she picked it up shortly after the Battle of Tairon and doesn't want it to get damaged.

He says that's not the point, she should publish it. He scoffs at her keeping something like that as an antique and asks if she's even read it.

She explains yes, she has read it, it's her favorite, she has it memorized.

He hesitates a bit and asks if it's good.

No, she replies coldly as she turns back to writing, it's horrible.

She goes back to writing, jotting something down, pausing for about 15 seconds, and writing some more, after several iterations of this she notes annoyed that he's still there. He asks how long she's going to keep working on her memoirs, and she explains that she has to fill the library from wall to wall quoting the exact description we use in Pyren's flashback when he realizes what's in the books (she knows exactly how much she has to keep writing because she's read Heyoke the Wolf).

After she makes that quote (which Jagex and the reader doesn't realize is a quote yet), she makes some snide comment about wishing she didn't have such a big library and laughs for seemingly no reason like she's psychotic (she comes off as bipolar because of these unexplained bursts of laughter or sadness, which make complete sense from the perspective of her time loop).

He keeps standing there, chewing her out. She sighs and opens up a new page, quickly jots some things down, and slides it to him. But he doesn't look, he's still talking, but then he glances down and sees she wrote down everything he was going to say, as well as his state of mind when as he reads in horror that she wrote down everything he was going to say.

He looks at her, confused and terrified, and she calmly reiterates her request for him to continue training (which is what she told him when he first came into the library.)

This book later shows back at the end of his flashback when he realizes she's still carrying it in her sack.