Everything in the world of Evorstrom is classified by Sign; society, culture, family, food, religion, government and even art.
The relationship between Signs dictates not only what people can eat but how their culture treats people of differing Signs. There is actual, measurable antipathy between opposing Signs and a near mindless sense of devotion to the people and places of a persons' own Sign.
Long ago a system of governance was enacted by a particularly benevolent Saint that aligned all eight Sign religions under a single pact that helped curtail violence between opposing Sign civilizations. They created a representative Parliament made up of elected officials from the nobility, the commoners and the clergy.
Within the Churches, established religious doctrine states that every five years one Sign is "ascendant" and is granted tie-breaker voting power on the Council of Clerics, the elected group of clergy sent to serve in the Parliament. When their term ends, the next Sign (moving clockwise) on the Circle is granted ascendancy.
However, in practice the two Churches aligned with a living Saint tend to wield dominant influence over the world during that Saint's lifetime regardless of which institution currently holds ascendancy on paper.