You should notice the comments about unity popping up in religious scenes throughout the book. Omin spoke of it before, and Hrathen often thinks–or mentions–the concept. When designing the religions of this book, I really wanted them to feel authentic. If you look at our own world, one thing is obvious (I think) about the way major religions work. They always fragmented–different sects of the same teachings often rise up and squabble with each other. Judaism, Islam, and Christianity share obvious links. In a similar way, Hinduism, Buddhism, and other eastern religions share some common roots.
So, in designing the Korathi and Derethi churches, I decided to give them a common ancestor–Shu-Keseg. All three religions came from the teachings of a single Jindoeese man. (You might note that the word "Shu," as used in connection with Shu-Korath and Shu-Dereth, doesn't seem to fit the linguistic styles of Aonic or Fjordell. This is an intentional reference to the Jindoeese commonality of their origin.)
The central tenet of Keseg's teachings was unity, and his followers began to squabble about what he meant by "Unity." Hence we have the loving, inclusive Korathi; the aggressive, expansionist Derethi; and the contemplative, didactic Jindoeese.
Of course, Jesker and the Mysteries are a completely different religious line. We'll get more into them later. . . .