The Song and the Rule
The Song- There is magic in the Seven Kingdoms. No one can deny this; it's everywhere and it permeates everything. The oldest, wisest and wildest of the fey claimed to hear it like a great slow song, a tapestry of music to which the world dances. Hear it, and you'll understand secrets of the world. Touch it, and you can do things no ordinary person can. Understand it and you can change the way the world moves. With it, the elder fey could make mountains out of plains and hide entire cities under the roots of trees. But these times have long passed, and now, even among the fey, there aren't many who can still hear the Song as they could in the past, let alone manipulate it. Among humans, hearing the Song is an extremely rare gift. Such a gifted person can, in a limited way, change the world around them to suit their will. The extent and scope of this power varies by individual, but so does the danger in using the Song. Since they are untrained, and can never know just what they can and can't do, a person gifted with the Song runs the risk of getting in far over their heads and harming themselves and others by tapping in to greater power than they know how to control. Despite the risks, Song-users are almost always respected by others, especially thaumaturges, who envy their freedom and the pure, instinctive relationship they have with a force so fundamental to the world, yet one that a thaumaturge needs a complex code to interact with.
The Rule - When the First War ended, the Ancients decided they couldn't leave the humans unprotected against other magic-users that might threaten them in the future. Therefore, they devised a method to teach their charges how to interact with the Song. It is essentially a code, relying on the Ancient's knowledge of the Song's influence on the world and translating it into formulas, gestures, sounds and certain materials and objects that mortals can easily understand and access. This method was named the Rule, and the Ancients built three great schools in which to teach it. Everyone can learn the basics of the Rule, and they are taught to a great number of students (mostly noblemen and those with the money to attend prestigious universities) as a part of their education. However the learning curve between "the basics" and "actually being able to cast a spell" is extremely steep. People with the determination and the talent to become registered thaumaturges are few and far between, and even at that, the Rule Academies have few graduates.... Especially since not many young students want to enroll when they learn the course is at least a decade and a half long.
Those who manage to graduate earn the official title of thaumaturge, and the unofficial right to look down on those who haven't. Those unfortunates are given a variety of disparaging nicknames (hedge-witch, alchemist, sorcerer, necromancer...) and are usually found deep in the country, far from the scorn of their more educated counterparts. Since the Rule is a language, every person who uses it does so with their own "accent", making every spell unique to the thaumaturge that cast it. Ideally, decades spent with the masters of the Academies should make a thaumaturge's casting more uniform, but even the best practicing 'turges can't cast exactly the same spell twice. The result will always vary slightly, depending on their personality, their mood and the circumstances in which they invoke the Rule. That is the reason that registered thaumaturges belittle Academy dropouts or those who learn the Rule from other sources; their magic is even more varied, and in most cases, almost always unreliable.
There are are a few bookcases full of regulations for any Thaumaturge to follow in order to continue practicing their craft, but most of the Rule's principles are simple and repeated so often that no 'turge could ever forget them. Chief among them, laws forbidding to interfere with the fey, with the dead and with the wills and spirits of living things. Raising or tampering with the dead, any kind of mind control or attempt to trap or use a creature's soul are taboo and will most often be swiftly punished by other Thaumaturges. Many acts of alchemy, including the creation of golems, are also considered forbidden, since they require the theft of spirits or elementals (to grant the golem a link to the elements, and even occasionally to the Song) and the theft of a soul (in case the creator wished his golem to possess self-awareness to a certain extent so that they may be able to complete more complex tasks).