Of all the organizations I worldbuilt that one time, I think this is the one that has the most potential to actually be interesting and useful in other settings. This one, or the Miracose Order. Neither of them are really great as-is, but I’m leaving the work of figuring out how to sand off the rough edges to other people, because Comic Con is coming up and I want a buffer.
The sorcerers are a barely controlled society of black magicians and occultists. Despised by the Celestial Order and the Magi alike, the sorcerers are tolerated primarily because their cavalier approach to deadly magic means that they generate plenty of useful sorcerers for important and powerful organs of imperial government – like the legions, whose commanders are very often the most powerful military presence in any given province, and which typically hold enough power to squash like a bug any count or equivalent who threatens to cut off their supply of military sorcerers.
Each clan is led by an elder, and the clans as a whole are led by the grand elder, sometimes known as the heresiarch, a title bestowed long ago by the Celestial Order identifying the grand elder as one of their chief enemies (this alongside the leaders of the Miracose, the Magi, and the most prominent of the Patriarch’s Council which was then not-yet unified with the rest of the Celestial Order). Undoing the status of heresiarch bestowed upon these persons and their successors is difficult, as the hierophant responsible was in no uncertain terms speaking in his role as the alleged messenger for Alra and his angels when he made the proclamation. The Celestial Order quietly ignores this for the most part in modern times, but the grand elder of the clans frequently takes up the title as a point of pride. Even the mighty and widespread Church of Alra cannot defeat the sorcerers (or more accurately, their allies in the imperial legions).
Although the grand elder holds the highest position and represents the clans on the Imperial Senate, almost all internal decisions are deferred to a vote of the council of elders on which the grand elder’s vote is given weight only in that it breaks ties. The position of grand elder is held for life, and upon the death of a grand elder, they are replaced for their clan specifically by a successor chosen according to their clan’s traditions, whereupon the elders meet and vote upon who shall be the next grand elder. The previous grand elder’s successor within their specific clan has the deciding vote in the event of a tie.
Each clan is built around the family of the elder. A plurality of clans are primogenerate matriarchies in which the eldest daughter of the current elder succeeds her when she dies. Nearly as common is an absolute primogeneracy in which the eldest child of the current elder succeeds them upon their death. Rare, but not unheard of, are primogenerate patriarchies. Some clans instead operate off of enatic seniority, in which the oldest living female is the elder, cognatic seniority, in which the oldest living member of the clan is the leader, or agnatic seniority, in which the oldest living male is the elder.
The elder of a clan technically has the power to appoint whoever they like to any position within the clan that they like, and to change the succession laws of their clan to whatever they want. In practice, tampering with succession laws is extremely rare and appointments within a clan are generally given to close blood relatives over more distant ones, and favoring either females or males depending on the succession laws of the clan. Cognatic clans tend to have a noticeable but less absolute bias in favor of female succession, just because enatic clans are much more common than agnatic clans, so women tend to be over-represented in positions of power, which colors sorcerers’ perceptions.
Thus, it is often the case that an elder’s sisters hold the most important positions in the clan, the elder’s daughters serve as her lieutenants and aides (especially if the succession is primogenerate, meaning the eldest daughter in particular must be intimately familiar with how the position of elder works by the time current elder dies), the elder’s nieces will likewise assist her sisters, and any leftover positions are given to cousins. Those who marry into a clan are generally accepted as members, but even if female (or male in an agnatic clan) they rarely have any future in the clan. Only their children are part of the bloodline.
The function of the clans to the Empire, the reason the clans are protected from their many religious enemies, is to supply various types of sorcerer to other organizations, most notably the imperial legions, although the archons, the praetorian guard, and several of the knightly orders also accept either instruction from or recruits sent by the clans. Each clan is thus tasked with producing sorcerers fit for purpose. Typically, these are the lesser men of the bloodline, nephews and cousins, while the elder’s brothers are reserved for marriage into other clans to keep the bloodlines pure without devolving into incest.
Each clan consists of a de jure maximum of 169 members, thirteen covens each holding thirteen sorcerers (de facto each coven tends to have dozens, sometimes over a hundred, members as distant cousins are quickly trained to be shipped out to the legion). The primary coven is that of the elder herself, containing her, her husband (the brother of another elder, usually), at least three daughters and their husbands, and five assorted others, usually nieces, cousins, or sometimes sisters who couldn’t find a place in other covens.
Sorcerers are long-lived and an elder can easily live to be a great grandparent with hundreds of great grandchildren. This means that after just four generations, the great granddaughter of the clan’s founder, now the elder, will have hundreds of second cousins each of whom have hundreds of great-grandchildren of their own, for a total of nearly two orders of magnitude more than the clan’s maximum. Every time a child turns thirteen they are (supposed to be) inducted into the clan, which means someone else needs to be removed. This means the coven is constantly expelling sorcerers as soon as they can be trained to make room for more.
The most common of these are the diviners. Trained in only the most basic of sorcery, they can cast runes and read their divinatory impact, come together to form scrying circles that allow distant locations to be seen, and send messages across great distances. Because they are quickly trained, the vast majority of third, fourth, and fifth cousins (with a fourth cousin once-removed valued about as much as a fifth cousin, and a third cousin twice removed the same, and a third cousin once removed valued about the same as a fourth cousin, and so on) are trained as diviners and then pushed out in their mid-teen years to make room for new sorcerers. Since they’re the most distantly related, men and women are held in more or less equal esteem (very little) and so diviners are as likely female as male outside the clans. No less than nine of a clan’s thirteen covens are dedicated to training diviners. Usually these clans are led by the elder’s sisters and any surviving aunts. In practice, some number of cousins or nieces are required in addition.
While diviners are common, warlocks are the most important. Trained usually in elementalism, but sometimes in diabolism or necromancy (depending on whether the legion they train warlocks for will even accept black magicians), they are sent to the imperial legions to provide them with magical support. Most of the men too important to be a diviner but not important enough to be married into another coven will become warlocks. Some of the more distantly related women may become warlocks as well, especially if they have a lot of siblings and that crop needs to get thinned before another generation hits. Second and first cousins usually become warlocks, weighted more towards the male than the female. While diviners are usually no more than fifteen or sixteen when their training is complete and they are sold off to the highest bidder, warlocks are usually in their late teens or early twenties when they are given as tribute to the legions. Three covens are dedicated to training warlocks. These are traditionally led by the elder’s daughters.
The most powerful sorcerers are the planeswalkers. Those who remain in the coven indefinitely are eventually trained to this level, learning lumen and shaman magic that allow them to travel between planes in addition to basic divination and the elemental powers of the warlocks. These sorcerers are more often female than male, and rarely leave the clans. The elder’s own coven is in charge of training these, and appointing them to the other covens. Planeswalkers are usually the elder herself, her daughters and sisters, and a small handful of cousins and nieces. The cousins and nieces are occasionally sent away from the clan, but generally speaking planeswalkers remain within the clan.