Spell formula

Used in the creation of permanent wards and magical items, spell formulas anchor spells into a carefully-crafted diagram to make them persist indefinitely. The anchor must be able to withstand the mana being channelled through it and it should not disrupt the spell boundary as much as possible, which may necessitate the use of exotic materials in anchor construction. Spell formula require high knowledge of mathematics and magic theory to use well, though simply copying existing schematics is relatively easy if one is already available.

Spell formula are notoriously difficult. Even copying an existing spell formula can be challenging, requiring high manual dexterity, a lot of patience and an ability to cast and anchor all of the spells necessary to create the final product. Additionally, if a mage wants to modify the diagram even slightly, they need a lot of theoretical knowledge and mathematical expertise to pull it off. As such, spell formula experts tend to be very rare and well paid. A lot of people dabble in it, however, since high demand for spell formula experts makes their services too expensive for many.

There is only so much you can cram into a spell formula, it is mostly dependent on the size of the item used as a base. Turning a ring into a spell formula for three different spells is a impressive feat. (ch.9)

## Nora's class

Spell formulas are the practice of using geometric shapes and various sigils to limit mana flow along pre-determined pathways to modify spells, usually in order to strengthen wards or amplify spellcasting.

The narrower the effect of the spell is, the more mana efficient it becomes. Structured magic creates a spell boundary to forcibly narrow down effect space into something manageable for a human spellcaster. And spell formulas are the exact same thing, only with more pronounced benefits and drawbacks.

Since mages can take their time when crafting the spell formula, they limit the mana flow much more tightly than your typical invocation. This means bigger potential benefits, but also makes the spell even more inflexible. And the tighter spell boundary means there is less margin for errors, so designing a working spell formula is a lot harder than designing a working invocation.(ch.11)

Spell formula are support magic. Magic affecting other magic. By itself, even the most elegant spell formula is merely a theoretical exercise. You need to actually cast the spells and anchor them to the spell formula before it's of any use.(ch.11)

### Beginner's cube

The standard training tool for spell formula. It is a perfectly cubical block of gray stone, each side roughly 10 centimetres long. They start completely blank and smooth. Finished ones did things like heat up, shed light, or float in the air when activated, or when certain conditions are met. Each finished cube is a crude magic item that uses a couple of simple spells and a whole lot of spell formula to produce a neat little toy.

#### The cube Nora assigned

At its core, a glorified lamp using a simple 'torch' spell as its base.

* Activated and deactivated verbally, by saying one of the several command words.
* Be able to tell when someone was referring to it specifically, as opposed to using the command word in some other context.
* Three different brightness settings.
* Conserved mana by not shedding light from any side that was covered by something - the side resting on the floor didn't shine, wrapping it in a blanket would cause it to turn itself off.
* Each individual side could be turned on and off by tapping on it twice in quick succession.
* Keyed to a specific person, taking orders from him or her alone.

### Compressed spell formula

Done when there isn't enough space to represent it fully in its raw form, and to stop others from simply copying the entire thing line by line.

## References

1. ↑ Disciplines of Magic (Worldbuilding Post)