Researching Persian Mythology for my book was no easy task. The timeframe had the Persian Empire at the height of size and distance of ground. Since several cultures were under the Kingship of the Persian ruler, it did take some doing to discover the true Persian Mythology at that specific time. Other cultures such as North Africa, Egypt, India, Greek, and Babylon were part of the Empire; but that was not even the entire list of cultures.
So, how to find the root culture used by the Persian society? The best way to write a book is to buy other books. I started to build a research library for myself with Greek and Persian texts of various things. I even have an Encyclopedia of Mythology, which is VERY helpful because it has all cultures, not just Greek or Persia in it. I also got a book called Persian Myths, by Vesta Sarkhosh Curtis. That book looks like it was used at the University of Texas, which I always wanted to go to when I was younger, so it all worked out well.
The Persian Myths book helped to set me in a proper direction. It also showed me a bit about the concept of their mythology. Instead of having gods that embody many of the personalities or behaviors of mortals (like the Greek Mythology does), the Persian Mythology has their various gods broken into good and evil in nature. Ahura Mazda is the King deity and is known as the Lord of Wisdom, hence good! His twin brother, Angra Mainyu is the Lord of Evil, no translation needed there. They might be twins but look NOTHING alike by the way.
After further research, I discovered the religious group these deities were most worshipped by, the Zarathustra and Zoroastrian religion. I believe the Zoroastrian religion still survives, but in the Persian culture of today, the dominant religion is, of course, Islam. I was highly intrigued to find that the Zoroastrian religion is one of the longest lasting in the world’s history. I would assume Jewdism is right in there too. Do you know of others? Do you know when they began?