Troyosha heresy

The Troyosha heresy, often called the new gospel, is a religious doctrine espoused by the Casiric High Priest Sorhan, declaring that the gods Casir (known in other lands as Set, Zehir, and Iyashkabar) and Nyssa (known in other lands as Tiamat, Takhisis, and Thala) are one and the same.

Meta

In real-world mythology, Set was sometimes identified with the Greek monster Typhon. In turn, Typhon was sometimes equated with the Mesopotamian goddess Tiamat—both were serpents defeated by storm gods. Just some food for thought.