I like most of all Charoite 1307 for the book.
It will look with gold letters very well and will have something in common with the dust jacket of the first set. It is important to have dark background. Gold letters on that light green background will not work. Need the contrast.
I do not really like the idea of ??the logo with the surrounding gold bead skulls. Skull is a very specific topic, and no everyone loves this. This could badly affect the sale.
I suggest to depict the realistic full-color logo like casted of gold for the front cover of the dust jacket. For the background, it would be good to create the dramatic sky with storm clouds and lightning and fill the entire background of the cover (including the back cover). It will look like a very impressively. What do you think?
Also, I would make a golden logo on one of the books as a stamp.
Regarding the menacing Wizard for the book it is not a good idea. I think It will scare away buyers. Maybe it would be better to make one of the subjects as a stamp.
But if you insist, I can do the evil Wizard. Then it would be logical to do so:
Book 1. The logo as a stamp for the book and the realistic logo and background for the dust jacket.
Book 2. Wizard as a stamp for the book and the realistic Wizard's face for the dust jacket.
Let me ponder this. I appreciate your thoughts and energy. We are ending a hurricane here so it may be a couple of days.