Most realms are either straightforward monarchies ruled by a leading military clan or theocracies governed by a high priest or a monastery. A minority is some sort of republic, typically a merchant oligarchy, or divided into small “feudal” domains build around fortified family strongholds. Both tend to collapse into a more centralized authoritarian regime after a few generations.
Though there are no authorities over the region as a whole, either in legal fiction or actual fact (there has never been a “Chigan empire”), there are some cultural traditions which at least give Chigan a framework for interacting with one another. Many of Chigan’s more powerful families are connected by marriages arranged to create alliances between them. However, since new marriages are arranged to facilitate a constantly shifting set of alliances, actual loyalties are quite muddled. Instead of a family in valley A being allied with one in valley B but not valley C, it’s more often the case that A has lines of communication with B and C (to say nothing of D, E, and F), and will actively cooperate with the one which gives it the most advantage.
Valley realms are not known for their warm relationships with one another. Cross-border raiding is common, but larger actions are rare. Even ignoring the problems of marching an army up one steep hillside and down another, it’s very easy to fortify the few viable passes into a realm. Small guerrilla forces of expert climbers can make more difficult trips across unguarded areas and disrupt a neighboring realm, but invasions in force are vastly more difficult. Where open warfare is practiced, it is usually preceded by softening up the enemy by some combination of supporting internal discord (sponsoring a revolt is very common), targeted raiding, and blockades, usually in cooperation with neighboring allies. However, the realms are generally, though grudgingly, at peace with one another, and so a certain amount of trade can go on between them.