This adventure was designed as a one-shot. The PCs who played it when I ran it are unlikely ever to be played again. As such, I did not worry over-much about how much gold and loot I was throwing at the PCs. It’s decidedly Monty Haul. If you are running this as a side-quest in a larger campaign, I recommend dialing back the treasure, particularly the rewards offered by Nazmi.
Alternate Quest Giver
Speaking of Nazmi, I selected her as the quest giver for this adventure simply because it would make sense for the Ruby Prince to be seeking the powerful relic that is the Scrolls of Thoth. If you would prefer to avoid directly entangling your PCs with the affairs of the royal house of Osirion, I recommend using Ruzben Seliman as the quest giver instead. In this variant, he is an independent wizard based in Sothis who has discovered the existence of the Scrolls and identified the location of the tomb. However, he prefers to hire others to undertake the task of actually retrieving the Scrolls. Adjust the introductory dialog to suit. The rest of the adventure can be run normally.
The most direct inspiration for this adventure was the Tale of Setne Khamwas and Naneferkaptah. I am not sure of the provenance of the specific translation linked here, but there is a more scholarly write-up in Ancient Egyptian literature. / Volume III, The Late Period by Miriam Lichtheim. The story is a late egyptian tale recorded in demotic about the much earlier Setem Khamwas, who was historically one of Rameses II's sons. In this tale, Setne seeks to retrieve the lost Book of Thoth from the tomb of an even earlier prince and magician, Naneferkaptah. I was much taken with the scene in which Setne is confronted by the Ka of Naneferkaptah's wife, who warns him against stealing the book.
That led me to wonder: how could I integrate ka, ba, and akh into the world of Golarion? The afterlife, as envisioned in Golarion world lore, generally presumes a unitary soul: one creature, one soul. But the real-world religious traditions of ancient Egypt were predicated on each person having a complex, multi-part soul consisting of a jb (heart), ren (name), sheut (shadow), ba, ka, and akh. Of these, the ba, ka, and akh were most closely similar to existing Golarion world lore, so I focused on those.
The solution I arrived at was that only a few ancient Osiriani had multi-part souls. Specifically, reading the Precepts of Maat from the Scrolls of Thoth caused your soul to be divided into a Ba and Ka, which then would need to be reunited in death to form an Akh and be judged according to the Precepts. Since only Pharaohs (and perhaps their immediate family) would read the Precepts, most people would continue on with unitary souls and be judged by Pharasma in the ordinary way. It was only the royals that really needed all the trappings of mummification and the elaborate rituals to reunite their sundered souls. Naturally, however, people who didn't technically need those trappings began adopting them anyway, in imitation of the Pharaohs. And thus we get the whole culture of elaborate burial rituals flowing from a requirement imposed by the gods on the rulers alone.
Overall, I'm pleased with the result, and I hope you enjoy it.
Here are a few of the resources I consulted in the course of writing this adventure.