Primal Hunter 5 by Zogarth 

Excellent book. I had my doubts when I read this would be all about the Treasure Hunt, but it worked. The author is covering a lot of new ground with every book.⬅️ Having been around a bit, I found the name Yalsten to be de distracting, I kept wanting to read it as Ralston, the company who used to make Wheat, Rice, and Corn Chex cereals. The brand was formally known as Ralston-Purina, with the Purina part being a manufacturer of numerous animal feeds and pet foods. So with the association to Purina Puppy Chow, whenever I saw any of the Chex cereals, my mind had an ongoing joke, thinking of them as "Purina People Chow". And I remembered that almost every time I read Yalsten. Probably nobody thought of this but me, and I'm weird.