An amalgamation of two religions that was created after the Wei and Jin peoples became one, Zu-Xi'an is the primary religion of the Weijin Empire. Although to consider it a religion for the Empire in the same way Ascensionism or Universalism are for the other nations of Terranis would be a bit of a misnomer. While the religions of the other nations are much more structured and codified in their beliefs, Zu-Xi'an exists more as a series of concepts, with no central clergy beyond a handful of appointed clerics who serve the Emperor or regional rulers, and its practitioners are often highly individualized in how exactly they follow its teachings.
Among its central concepts is the “Path of Heaven”. Indeed, “Zu-Xi'an” itself is a shortening of a phrase which roughly translates to “Balance of Heaven”. All humans are believed to be walking the Path, and how far they travel along it depends upon their temperament in life, their deeds committed, and their overall Balance.
Perhaps owing to the disciplined influences of the Jin, but also recognizing the need for it between two different peoples, Balance is a vital element of the Path. Negative or passionate emotions are not suppressed, merely acknowledged, channeled appropriately, and balanced with those in opposition. Likewise bad deeds, while avoided when possible, are sometimes unavoidable, and, to restore Balance, an individual feeling guilt over a transgression may commit themselves to service in a temple or some other means for an extended period of time. The closest thing to a symbol that represents Zu-Xi'an is the Yi-Yan, a popular image representing Balance in all things.
Deceased ancestors, as long as they were not reviled in life, are generally venerated to varying degrees, and are viewed as continuing their journeys along the Path, traveling far further along it thanks to being freed of physical concerns. As such, their examples are looked up to, and it is not uncommon for a living individual to pray to their forebears for guidance or wisdom in times of difficulty. Although there are some theistic elements to Zu-Xi'an, the prevailing wisdom is that one's direct ancestors will be much more willing and ready to provide assistance.
In terms of cosmological makeup, typically adherents acknowledge the existence of an omniscient Creator, much like the other religions, however He exists more as a nebulous concept, a being who exists so far above the mortal plane that humans are generally beneath His notice, and we lack even a fraction of the capacity to truly understand Him. Closer to our existence, however, are assorted spirits, animating forces that can be found in the stars of the sky, the world itself, or even to smaller degrees in individual plants and animals or specific locations. Shrines or temples may sometimes be built in specific places to honor these spirits, providing both a home and protection for them.
The corruption of the Great Enemy is therefore seen as the greatest threat not only to these spirits, but humanity as a whole. Every aspect of the demons goes against Balance, and to embrace them is to not only fall off the Path, but to leap from it, into an inferno of destruction. During larger conflicts, normally-stoic warriors may suddenly fight with relentless fury to protect a shrine dedicated to a local spirit, refusing to let the Great Enemy bring its corrupting influence forward. Many shrines and temples will have a small contingent of volunteer warriors who defend the place from attack, and otherwise devote themselves to continual meditation.
This is perhaps the closest thing to religious fervor seen in the Empire, as there is little proselytizing performed either within or without the Empire. Although a few small shrines can be found across Terranis, built by those who have left Weijin and still feel a connection with wherever their travels have taken them. Not surprisingly, the more rural practitioners of Zu-Xi'an find much in common with the Druid clans, and it's not unheard of for a temple in the wilderness to have a working relationship with a clan in the area.
In everyday life, the practices of individuals can vary wildly. Common practices include daily meditation, reflections on scholarly works by notable writers such as Wen Chi'an or Manomo Hasuda, prayers to or even simple conversations with one's ancestors, visiting a shrine or temple for guided prayers or meditations, pilgrimages to specific shrines or temples, charitable works, wearing heavy clothes that required considered movement and action, studying the stars for any potential signs or portents, and more. A given individual may observe any combination of these, or even none at all. Typically little emphasis is placed on following any specific practices outside of familial concerns, as the Path is viewed as something personal and specific to the individual.
As mentioned, little external missionary work is performed by the Empire, but, even so, elements of Zu-Xi'an have begun to appear across Terranis among non-Weijini. Whether drawn to the stark differences compared to Terranis' other religions, or interested only in the daily practices such as meditation, a growing number of people in every nation have begun adopting practices of Zu-Xi'an, in many cases considering themselves adherents of both it and another religion (typically Universalism). Although some hardline elements of the Ascensionist church, and even some small parts of the Universalist one, have pushed back against this, most have been welcoming, finding far more common ground than uncommon in the beliefs and practices of all three religions. Only the growing isolationist attitudes of the Empire over the last century have slowed Zu-Xi'an's growing adoption among the other nations of Terranis. Whether Balance is restored to the Empire soon or not remains to be seen.