Thaumaturgy is the art of multiple people working in concert, through the medium of ritualistic gestures, symbols, intonation and actions, to create elemental resonances and dissonances and affect the world. Specifically, thaumaturges can learn to manipulate the world through the use of Rituals.
Taking the Lead Ritual skill for an element grants the ability to improvise rituals of that element, and knowledge of the formulaic Consecrate ritual for that element. There is no restriction against learning to lead opposing elements.
Additional formulaic rituals can be learned by taking the Learn Ritual skill, learning two formulaic rituals each time.
Rituals are performed by channeling power through the ritual participants, who must control it. Power is most easily drawn from silver, in the form of Ducatto.
It's possible other substances will be found that can be used as power sources in rituals. If so it's likely they'll only be usable in certain types of ritual.
The easiest way to control power is to increase the number of participants in the ritual. Each participant can safely control one Ducatto of ritual power. By pushing themselves, the lead can control one additional Ducatto.
If any of the raised power is not controlled at the conclusion of the ritual, the ritual will still succeed but fallout occurs.
For each Ducatto of power that is uncontrolled the attending ref will resolve a card of fallout at the conclusion of the ritual. There can only be as much fallout as there is controlled power, or the ritual is cancelled.
There are no set rules how a ritual must be performed, and different thaumaturges perform rituals in wildly different ways. It seems as long as the participants believe it will work, it usually does. However, activities that involve the participants working in harmony are known to be particularly effective, such as chanting, singing, dancing or other ritualistic movement, or making music
Some rituals can be cast on multiple targets with a single ritual performance by causing the ritual performance to “echo”. For all intents and purposes the ritual is cast multiple times at the completion of the performance (including consuming the resources for all castings), but only one performance is required. This can only be done if the ritual causes no fallout (should it somehow unexpectedly cause fallout, it is performed once and stops).
During the darkest moments, a thaumaturge can draw on a measure of last resort. They can shorten the cast time of a ritual to 10 seconds. Such fast channelling tears through the body of the ritual lead, causing them to become terminal after the effect of the ritual is discharged. Fallout from rituals done in this way is directed in to the ritualist instead of outward, effectively negating it, but you can still only have as much fallout as there is controlled power or the ritual is cancelled.
It’s possible to use souls to power a ritual. This requires a willing possessor of a soul to be present that the ritualists can draw on. The soul of a single human can provide 8 Ducatto of power, with the added advantage that this power does not need to be controlled by the ritualists - its sentient nature means it readily follows the thaumaturge’s designs. Souls of participants or the lead can be used. Consuming someone’s soul kills them instantly, after the effect of the ritual is discharged.
The Consecrate formulaic ritual is learned by taking the Lead Ritual skill, and more can be learned with the Learn Ritual skill. New formulaic rituals can be created by performing an improvised ritual then codifying it in downtime.
Thaumaturges can design custom rituals that go beyond the scope of codified thaumaturgy.
Once performed successfully an improvised ritual can usually be codified in downtime, making it a ritual that can be performed reliably.
When improvising rituals, you may want to bear in mind the limitations of all natural philosophy, which includes thaumaturgy. Thaumaturgy also has a couple of additional limitations.
Divination using magic (even Order magic) tends to be rather subjective and dubiously accurate - mundane investigation tends to be a more certain way to draw conclusions if it's usable. The exception is analysing the elemental properties of things, at which magic is usually the best tool for the job. If you have very little information, divination could give leads to build on with mundane investigation.
Largely a corollary of the Law of Presence, divining the present in other locations, or the future, is impossible. Divining the past of an item, character or location that’s present is possible. Divining information about the present of your current location is possible, but mundane investigative and pathology skills are usually better tools for the job.
Performing the same ritual (or an improvised ritual with a similar effect) on the same target twice in one day is likely to be much less effective than usual and may be dangerous. This is especially true if performed by the same lead.
For some reason, thaumaturgy effects tend to break on sunrise. Making an enchantment that lasts longer than overnight is very hard.
Alice, Bob and Charlie are on a linear together and hear that a group of enemies is coming to get them. Alice has mastered the Ruination ritual, and they have a little time, so they decide to prepare it.
The ritual can summon one destructive bolt per Ducatto of power. They decide that they'll all participate, which allows them to control 3 Ducatto, so they get out the coins and start the ritual.
The enemies come early and the ritual isn’t quite done yet, so Charlie decides to leave the ritual to keep them busy. The ritual will now have one Ducatto of uncontrolled power. Alice decides to take a wound to control this power and the ritual continues.
Charlie isn’t faring too well, so Bob also decides to leave the ritual. Alice can’t take another wound to control the power. Since there's a ref present, she decides to cause fallout rather than cancel the ritual, and informs the ref of this.
The ritual completes and the ref draws a single fallout card, which is MASS MAGIC TRIPLE, and calls it. Alice then takes a WOUND call due to her wounding herself to control extra power (she currently has no mortal wounds, so is fine, for now), and unleashes 4 MAGIC TRIPLEs on the enemies. The party wins, and since it's now the end of the encounter, Alice asks the ref for her mortal wound card.