(Some of these may move elsewhere, or become pages of their own).
The language spoken by the inhabitants of the Twelve Kingdoms is Xiang. The Northern Barbarians speak Torghut, and the Southern Barbarians speak Senatali.
Gender and Sex
Many of the traditional social structures are patriarchal. For a woman to lead a kingdom, or fight as a soldier, is not as common as for a man to do so - but it is a genre with a lot of unusual people in it. Multiple wives are not uncommon in noble/rich families.
A young woman who is a Great Prize for marriage is expected to be a virgin. Once an unmarried woman is old enough to run her own household (i.e. no longer in the "parents are arranging her marriage" category), taking a lover is less remarkable. A married woman is expected to behave with discretion, so that none will be able to criticize her.
It is more expected that men will be having sex, though married men are also expected to behave with discretion.
Some men are made eunuchs - sometimes to ensure that an advisor's loyalty is to his liege rather than his own family and children, sometimes in a job which involves guardianship of women.
Prostitution is generally legal; of women is more common than of men, but there are both. For a married person, visiting a prostitute is more discreet than carrying on with a friend.
There is a fairly strong class hierarchy (peasants are more like serfs than slaves), and tradition of being deferential to anyone who outranks you on any of several axes (rank, age, learnedness, spiritual piety...). The average person follows in the footsteps of their parents, and doesn't rise at all, but there's a lot of potential for the person with talent and stubbornness to take a different path. The most common is to study under a master - this lets the student rise to the same class as the master (modulo age and learnedness). A great lord can reward someone by making them a lesser noble. People can join one of the Five Temples and eventually become a revered monk. Rarest of all is for someone to rise through their own actions alone (with no teacher or lord or spiritual guide), but it is not unheard of.
There are the Five Temples, and many spirits of various sorts (ancestor spirits, animal spirits, rattle-headed forest spirits...). Shrines to ancestor spirits are most common in noble families, but are not unheard of otherwise, and there are also shrines here and there, especially in the wilder areas, to venerate and placate a local spirit. The 12 spirits of the Cycle receive particular veneration, often from those touched by each. There are generally believed to be gods, complete with a final afterlife, but they are remote and not particularly a focus of worship.
The money of the Twelve Kingdoms is generally thin round coins with holes in them, carried on cord, in the following denominations:
- Tael (~gold)
- Li (silver)
- Zhu (copper)
1 tael = 100 li; 1 li = 100 zhu
Tael can only be minted in the Hidden City. Due to the method of their minting, tael coins cannot be melted or nicked, and are generally considered impossible to forge. They glow ever so faintly in complete darkness.
Li and zhu are permitted to be minted locally, though with very strict accounting to the Regency Council. Zhu are frequently clipped in half or quarters.
For very large commercial transactions, the House of Judicious Increase in the Hon'eth Arcade is often used; both parties will deposit the money or goods, and the house will oversee the trade (for a fee). They will also provide letters verifying that particular amounts have been deposited in their coffers at a particular date.
One zhu is worth (very approximately) one modern dollar.
Most countries maintain some sort of public mail service. It does not run every day, nor can it deliver everywhere, but where it does deliver it's usually considered reliable. Most people can pick up their mail at the local town hall if they are expecting something.
Large merchant houses and important government offices will tend to use their own couriers, when the regular mails are not sufficient.