The Church of LAW
Back in the day I used to play in Miranda's Nightwick Abbey game, if you haven't checked out her blog or her Patreon you should.
She had the gimmick that the medieval church was espousing the RPG rules themselves. She however is an actual scholar in medieval history and so carefully interwove real history with her references to the game rules.
I had previously been using "The Church of Spartacus" as my dumb medieval church knock off, and this was way better. Alas I am not as subtle or clever as Miranda so my version is a whole lot more obvious.
Behold the writings of the famed Pedantius, scholar of the church of law
In the beginning, in deep in the holy lands of the middle west, there was a proclamation of THE LAW, the metaphysics that shape our world. And it was St. Gax and St. Arn who heard the revelation, and they went and proclaimed it at the festival in the holy city of Geneva.
They wrote the sacred texts in a trio of brown codexes and preached THE LAW. St.Gax realized the need for an organized church and so founded a church to organize moneys with which to launch crusades against the haunted dungeons that plagued the land. Proclaiming that one would receive indulgences and forgiveness for extracting gold from their cursed depths. St. Arn then wandered off peacefully with no desire to part of the church or its activities, so sayeth the church records signed by St. Gax himself. And for a time it was good.
Then the Holy Mother came to the church for she knew it was time to expand into other lands and to expel the demons and devils. So St. Gax willingly left the church to set off on a Lejendary Adventure, so sayeth the church records signed by the holy mother herself. And the church did enact Vatican II and shifted its crusades away from the dungeons and to reach new lands. Some crusades even went to other planes it is said. But the lack of gold recovered from dungeons put the church in severe financial strain.
So too did a group of magi come from the coasts of the far west and rescue the church. They enacted Vatican 3 and set about a code of strict legalism, where all things could be adjucated by the rules. It is then that it is claimed they made a set of changes called the "Apocryphals" to create a bastardized Vatican 3.5, and there was much gnashing and wailing of teeth, especially in the north lands ruled by King Osric, once a powerful adventurer himself.
In the decadence that followed the wizards rejected THE LAW and tried to create a new set of edicts known as the cursed and forgotten Vatican 4. In response to this, the rumblings in the land of King Osric flourished and the angered peasantry took advantage of the legal loopholes the Wizards themselves had created to found the "Originalist Scriptural Reformation". This set of "protest teachings" was run by decentralized churches who sought to return prior versions of THE LAW. And for a time it looked like the Holy Church would fall.
It was then that Mearlin and a few other wizards from the far western coast set about to create a unified Vatican 5 to turn away from the blasphemies of Vatican 4. But much damage was done. Not only had the protestant Original Scriptural Reformists rebelled, but even among those who followed the teachings of the coastal wizards, a branch had broken away to try to "Find the Path to salvation that had been lost".
Rumblings of a Vatican 6 persist, one that offers "Salvation as a Service" to try to boost the finances of the church.
Of course some other faiths also persist that dare call themselves LAWFUL. Some attempt to follow what they call Generally Understood Religious Practices and Symbolism to create a universal faith. There is the secretive and heretical followers of THE CALL, who on the surface adhere to Basic Rituals and Practices (similar to some knights) but believe that the entities who exist outside of physics among the metaphysical are antithetical to the law, bending rules to a whim. They claim one such being ignores all sacred rules of the class of armour or how many hits a warrior can take and simply consumes 1 to 6 adventurers every six seconds. What heresy!
Even worse, there are those who follow the Devil whose true name I shall not utter here. They tell fortunes with the false polyhedral with ten sides and cavort with vampires and werewolves. They dare pretend to be Lawful while also clearly being Evil! As if alignments could exist on two axis at once!
Otherwise the world is mostly divided between the pagans who view interacting with metaphysics at all as wrong and only worship beings found within the bounds of the LAW. They worship gods and demons of good and evil but resist what they call "Metaphysicing" as an unfair practice. Though misguided, they are not true followers of CHAOS and are neutral in terms of the GREAT CONFLICT.
Those truly under the sway of CHAOS acknowledge the primacy of THE LAW but seek to twist and usurp it.
There are the FALSE PROPHETS who when using stones to read fortunes (as all adherents of the law should do from time to time) are prone to lie about the results of the stones and quickly snatch them up that others may not read them. They perform sorceries to attempt to hide the truth of their character from others and even THE LORD (also sometimes called THE MASTER).
There is the blasphemous teachings of the DESTINED PATH who believe that man was not truly granted free will by THE LORD and that he will twist reality to ensure that history follows a set path. Thus they believe they cannot truly do evil because their actions have no consequence. Their cults are known to frequently ally with the fearsome quantum ogres.
The most insidious cult of CHAOS are the ILLEIST CONCOCTERS who view themselves as equal to the creator. They proclaim their own ability to rewrite THE LAW as they see fit. In dark labs they create new monsters which have never before been documented by the church. Their practictioners follow careers and social classes that do not exist in the holy texts. Who knows what terrible new magics they have created?