Maids & Masters Lore Post - Master Theurgy
This is going up a little later in the day than I'd like, but I suppose a little late is better than not at all. This week I'm gonna get in-depth on how Theurgy relates to Masters, because while it is technically it's own classification (specifically, Compulsion), the setting is a little picky about who gets to say what about it. Largely because each family has their own secrets, and they aren't likely to share any of them any time soon.
As with the previous lore post, there are some spoilers for Act 2 in regards to Evdokia (and to a lesser extent, the second Haunt and Baleflight), so be aware of that before reading on.
Servants' Theurgy, in opposition to a Master's Theurgy, tends to be short term and comparatively inflexible. While Servants can have the ability to express their Theurgy in more ways than Masters - such as destructive Incantation, manipulative Vexation, or more physical expressions like the martial disciplines - the effects are rarely long-lasting. Those that are tend to either be passive Prestidigitation or need to be maintained, and the degree of expression largely depends on the Servant's grade. Compulsion can be immediate and momentary - such as with Orders - or it can be functionally permanent - such as with Contracts.
This difference can almost be seen in the same light as a Servant having their primary Theurgy and their Prestidigitation, with Orders being the primary Theurgy, and the ability to create Contracts being the secondary extension of their Theurgy, with the caveat that all Masters share the same Prestidigitation.
Though it would be more accurate to say that Contracts are a mutation of Compulsion. Since mutual consent needs to be given before someone is subject to Compulsion (the precedent for Pacts of Servitude), if both parties agree for a given effect to be permanent, it becomes permanent. This was first made evident by the early forms of Pacts of Servitude, as it has never been recorded that a Master has been able to issue an Order to someone other than their own Servants (despite some historical claims to the contrary; those instances lacked the proof necessary to officially recognize them).
From there, Masters realized they could modify their Servants to an extent. This includes things like modifying hair or eye color, dictating metabolism or muscle growth, etc; the subject's body is Theurgically compelled to make the specified changes.
However, to be included in a Contract and truly be effective, these can only be minor changes that a person's body could theoretically be capable of before Theurgic modification. If it is, the effect takes place without any additional cost or effort. If it is not - for example, changing a person's physique or bone structure, or attempting to predetermine how their Theurgy will express - regardless of what the Master does, the change will not take place.
No Master has ever displayed any further aptitude for Theurgy. Whether in terms of having the ability to circumvent any of these established rules, or obtaining for themselves the ability to express a Servant classification of Theurgy, all attempts have been unsuccessful. Even when rumored - such as with the fallen queen - the truth typically points toward the individual in question obtaining their Theurgy through other means, and claims of Compulsion being inspired by shows of loyalty or an effect similar to Compulsion, such as non-standard applications of Motivation.
Similarly, no Master has been known to "invent" a new type of Theurgy. Historical precedent shows that all instances hold closer to more modern definitions, and such legends are closer to the result of poor definitions or flawed understanding. This includes theoretical Theurgy like Mutation - the ability to change one's own form or another's through the application of Theurgy. Myths surrounding Mutation are either purely fiction, the result of unstable Theurgy brought on by the Haunt, or the result of an observation made by the uneducated.
What makes Compulsion unique is a Master's ability to reinforce or exceed what they're capable of by paying an additional cost. Servants pay that cost with their own Theurgy pool, a Theurgic reserve determined by a combination of the Servant's natural aptitude and grade. Masters do have natural aptitudes, but they don't have a grade, and their Theurgy pool is limited more by their proximity to their ancestral headstone than anything that can be written down as a numeric value. Instead of expending what would otherwise be a limitless reserve, Masters can spend Silcrow.
In theory, there's no upper limit on how much Silcrow can be spent to achieve a specific effect, but it's rare for a Master to be willing to weaken themselves in this manner for the sake of experimentation. A more acceptable reason would be that a Master intends to use brute force, such as forcing their consciousness into a Theurgic construct (for example, the mind maze, or a Theurgic barrier) or to aid a Servant in accomplishing a task much more quickly or efficiently (for example, Emily setting up shop).
Further applications require a great deal of non-linear thinking and taking advantage of how Theurgy behaves under certain circumstances. The Baleflight family in particular were attempting to explore the second phenomena in greater depth. The had created a system under which a Theurgic construct could accept an amount of Silcrow, then return a random amount of Silcrow through an amplification method. The Theurgic construct's purpose was to return the Silcrow put into it, with the amplification method repeating a percentage increase before the Silcrow was returned. However, this amplification loop would quickly become unstable, with early versions of the construct simply destroying themselves as the Theurgic energy was forcibly expelled. The most recent version uses fewer amplification loops, but as the energy still very quickly becomes unstable, the Silcrow may not always be returned, and over-use still results in the construct self-destructing.
The current Master of the Fairweather family, Duke Evdokia, is another such example. Through the expenditure of massive amounts of Silcrow, she has achieved an effect not unlike Mutation, though the method is closer to modifying a body through more traditional methods but on a larger - and much less stable - scale. Her method involves effectively overloading the tissues of a specific portion of the body, spending Silcrow to amplify the effect to the exact point where the body would overload, and stopping the flow of Theurgic energies before the body can suffer self-destruction. She'd never admit it (and her Servants are forbidden from speaking on it), but the initial experiments cost her several Servants, and though the process is now as close to perfected as it can be, it remains an incredibly painful process.
A closer example to true Mutation Theurgy is Marius Baleflight's experiments in the years preceding his death. By adopting Blodwerk, a long-forgotten alchemical process that encouraged minor physical mutations, and combining it with Compulsion, he was able to guide the process with a little more care and a lot less Theurgic energy. While this first attempts required him to use chunks of Headstone material to absorb the excess Theurgic energy to prevent self-destruction and resulted in the abominations he made of his fellow Masters, his final two attempts were more successful. They allowed him to use his "Blood Theurgy" to call forth and dismiss these alchemically induced mutations in himself (albeit at great physical cost), and ultimately stabilize these mutations in his daughter, Katrina, saving her from the otherwise incurable disease that had taken her mother.
An argument could be made that this means Marius Baleflight did actually invent a new type of Theurgy. However, given the costs of both the process and utilizing the final results, not to mention that Katrina is now quite literally part beast, it's probably for the best that his work is lost to the ocean beneath where his Estate once stood.