Below is a list of thoughts for possible research and unanswered questions related to the mystery.

The ZEBULON code decodes to “FOUR AND SEVEN BORN HIDDEN REVEALS THE CAVE OF PRINCESS TOCCOA”. It is thought that the “four and seven” refers to the code words hidden in the medicinedown image, but the rest of the code is still unclear. The four and seven add up to eleven, which ties in to the note sent to the shopowner where the book was allegedly bought.

The SPEARFINGER code decodes to “A CARD CHOSEN A SPELL IS CAST A DOOR OPENS”

In addition, the images in the Wendi channel (https://rhobard.com/sojoana/wendi) probably contain a hidden message, either in the images themselves or the captions and hashtags used. That's something else that could be examined independent of any deeper understanding of the mystery.

The music used in the videos, and referenced elsewhere, probably has meaning (https://rhobard.com/sojoana/music) so that's another area that can be studied independently. It would be great if we had a Japanese speaker to translate the lyrics to 1.66666, for example.

The codes on the flyleaf of the book and pages 513. Codes on page 515 and 636 turned out to be keys to other coded text.

were the pencil annotations in the book written by a different person from the pen annotations

the photos in the Allgood video (order, identification, reasons, etc.)

whether or not the music in the videos is relevant, and, if so, how

the entire geographic aspect to the video

the relevance of military/military intelligence references in the mystery

the meaning of the codewords on crossfiregambit.com

the meaning of the hidden codewords on medicinedown.com

the relevance of the US South (apart from its connection to the Trail of Tears)

Major themes of the mystery are: the Cherokee people and the Trail of Tears, music, cryptography, geography, military intelligence.