So you might come across some order in its public life or even get some legitimate work with some agents. You could even be working in an organisation that in secret has horrible agendas for a while before you join the higher ranks and hear about the ordered schemes. You could discover documents or witness that order is not what it seems. Perhaps a party will join to keep an eye on them or learn their secrets to destroy or reform them. A new character might start with an order patron and take years to discover the real order purpose.
My next frpg I will use a bunch of these
Some guilds, knight orders, sisterhood and secret cults in future
Obviously, these guys are toxic jerks who put forcewall ceilings on important wizard careers. I envisage them starting as a loved adventurer club then ramp up their true proposes and plans over time. I expect eventually their secret symbols will be known and the party will recognise wizard members by jewellery or tattoos
The Celestial Brotherhood
Public Goals
To promote the benefits of manly wizardry to the commoners and nobility
Create public works, monuments and improvements to aid the welfare of commoners
Wizards can meet to get discus community wellbeing
Real Goals
Have weekly secret meetings then drunken binges and singing and feasting
To conquer the world one kingdom at a time
To operate in secret so the common scum and idiot nobles never know
Keep women out of wizardry and even literacy is too good for them
Just summon or make better lovers if you need them, until then don't bother with them
Leaders
A great council of the 5 greatest wizards rule and occasionally there is a deadly duel to replace one (one is a lich unknown to all). Each kingdom has a lesser council of 5
Members
Suitable members are questioned in secret to see if they have the right aspirations. Some of these questions may be done secretly by different members so prospective wizard won't even know. Many are in academia or just regional backwoods wizards. A secret initiation ritual involves a test of your resolve and some who fail are killed if seen as too dangerous. Most of lesser ranks under name level don't even know about secrets
Followers
These are commoners and student wizards who join in hopes of being noticed or getting spells. Some masters give apprentices extra credit for working with the order. Others help the order because of their good deeds and charity
d12 Missions
1 Lady wizard has stolen documents and infiltrated lower ranks, find her/him, get back the records and bring this villain to the council of 5 before she slanders our good order
2 Bury these magic stones under various villages on kingdoms borders
3 This hunting lodge has a special meeting of the kingdoms five master wizards, we need to make sure no intruders try to intrude or spy on the meeting
4 This former member is really an evil foreign devil worshipper out to harm the order, find them and bring them back if possible but don't let them leave the kingdom
5 Tanke these medicine potions to this rural village, tell them it is from anonymous donors as they dislike wizards lots but we must help sort them out. Make sure you leave immediately perhaps explaining you have other villages to help
6 A delivery of sacred herbs for an order celebration is to be collected from the docks at night. Avoid unnecessary encounters with taxmen or law but use this order seal if stopped. Then get the box to this rural estate in time for the sacred rites and you will be rewarded
7 The older witch hunters are all retiring, go give them these donations and encourage them to teach a new generation to hunt these evil unregulated spell caster. The witch cults may try to stop you
8 This scriptorium we trusted to work on our documents has been distributing naughty parchments depicting order members in a compromising light. It would be best if the building and it's contents burn. Give this letter to the firewarden a day before. Make sure all documents in progress burn
9 A wicked sorcerer in the mountains has a terrible machine that spawns monsters, take this machine to the orders hall in secret, Kill the sorcerer leaving no remains
10 Take this porcelain golem woman to this important wizard and give him this sealed envelope with the magical commands. Don't even think about using the golem
11 Convince the mayor to shut down this young ladies magic school, we have made them move before, eventually, they will give up. Anything you can do to tarnish the school reputation or the staff will help
12 Take these frozen troll flesh cubes to the orders secret forest laboratory. The ice and straw in the crates they are in should get you there if you hurry without spawning a troll army. Avoid inspections and tollbooths