A Soul Oath binds a person's soul in service to another individual or organization until set terms are met, most often in the form of a time duration. The Oath is typically taken in exchange for something significant, such as advanced magical training.
The Chau were traditionally a migratory people -- but eventually, they settled near the river Honnun, which goes through incredible flooding seasons. Thus the Chau are a people of two cities -- Malun, and Chaujun.