Of the Quadrilunarum, arcane magic is the most deeply mortal. It is, in many ways, a mortal science; there are formulas and institutions, and there are many intellectuals who dedicate their entire lives to furthering the art of mortal spellcraft. Arcane magic grasps at the lunar-arcane and constrains it within mortal understanding.
The Foundation of the Arcane: Intellect and Willpower
Unlike the other three Magics of the Quadrilunarum, arcane magic requires nothing other than one's own intellect (study, memory, and understanding) and willpower (physical and mental resilience to guide the lunar-arcane). There are no blessings, no chaos, and no pacts. Arcane magic is gained, furthered, and limited by one's own strength or weakness.
How Arcane Magic is Gained and Mastered
Legends are many that tell of how much more abundant magic was Pre-Reckoning, and whether or not those are true, the fact of the matter is that anyone can perform arcane magic Post-Reckoning; however, it requires an extraordinary amount of effort (or luck), so much so that most people go their entire lives without casting the smallest spell.
Among those who do learn arcane magic, there are two routes: study (the vast majority) or luck (the vast minority). For most, arcane magic is like any other science: they study it, they practice it, and then they master it and do their own research. This is the realm of the countless arcane institutes and universities across Emaxus and greater Yophas. These mages and wizards study spelltomes, practice spells, and memorize arcane components and formulae. Through this, they learn how to draw the lunar-arcane forth and create the conditions for spellwork; then, they need only the mental will and physical endurance to spark the magic and let the spell fly.
Arcane Spellcraft
Because arcane magic is mortal magic (and akin to a mortal science), arcane spells are formulaic; they are theorized, practiced, and then shared. Arcane spells can be invented and codified. The art of arcane spellcraft is a dangerous one, as tampering with new components (or new combinations of components) can create spells with unexpected and dangerous effects, or that require a far bigger spark than the caster anticipates.
For this reason, one should typically practice and/or master spells of a similar effect and class to the hypothetical spell they wish to create. Thus, spell invention is typically relegated to archmages and master arcanists, either in code or in practice.
Rarer are those who grasp arcane magic by their own fortune (or misfortune, depending on one's perspective). These are the mortals with magic in their blood, be it from inherently magical creatures like dragons or from even rarer circumstances, like a pact of understanding (these are very rare exceptions to the above rule of "needing nothing but oneself"). These mortals gain access to magic by these extenuating circumstances, but they must still practice and master it like a person who learned magic through study. The main difference for these rarer folk is that they tend to have a magical predisposition which gives them access to the lunar-arcane with greater ease, at times even eschewing the arcane components needed in so many spells.
Regardless of how one gains access to arcane magic, the spellcraft plays out the same: one manipulates the lunar-arcane into a certain pattern and/or concentration, then activates that pattern with a spark of their own energy. Intellect is needed to manipulate the lunar-arcane; this is typically done with certain arcane components (which all have specific traces in the lunar-arcane), alongside runes, Titanspeak, or physical movements of the caster, like finger symbols or hand movements. Willpower is then needed for the spark; once the energy is gathered, one must impart their own force of will onto the lunar-arcane to "spark" the spell, as it were, usually with Titanspeak and/or a movement. This drains the caster's own energy, by a drop or a bucket, and thus willpower and intellect combine by way of how efficiently the caster can gather the energy and then spark it.
Take, for example, two casters trying to create a simple pyromancy to light a fire. One is a novice, the other a master. The novice takes time to gather the proper components, to mentally pinpoint their own spell's energy, and then a distinct mental and physical movement to spark the spell. This taxes them to the point of leaving their fingers cold and slightly numb, but the fire is lit.
The master, on the other hand, knows the components without thought, throws them to the wind, and ignites the spell with the faintest drop of their own energy and the lightest mental push necessary. In this, the master gives no more than needed and takes no more time than absolutely necessary---efficient in totality. Whereas the novice would take precious time and energy to recreate the same spell, the master could do it ad nauseum, so long as they had the components.
The Limits and Costs of Arcane Magic
Arcane magic is limited by its costs: knowledge, energy, and components. There is no such thing as mastering arcane magic; one may master a facet of it, sure (and it is for this reason that the schools of spells exist, to give categories and specializations), but one would be hard-pressed to learn every known spell with a thousand years of study---and every known spell is not every spell possible. Thus, one must choose what they learn, what they practice, and what they master. One may not know a spell, which means they should likely not try to cast it, although they could experiment (and risk draining more of their energy than expected to create an unexpected or undesired effect, if any). One may know a spell but not be well-practiced; thus, the spell is time- and resource-intensive, and they are limited in how much they can cast it. For this reason, mastery is coveted, but the mastery of a spell comes from the study and practice of it, and the more complex and powerful the spell, the more study and practice it takes. It might take months to master a pyromancy of sparks but decades to master a pyromancy that summons a firestorm.
Beyond knowledge, there is a question of energy, more commonly the stamina of the caster but rarely the energy of the lunar-arcane, too. It takes one's own energy to activate a crafted spell, and it tends to take more energy to spark larger spells. This will drain and sometimes even kill the caster if they do not know their limits. This is, of course, where knowledge comes into play, too, as practice with a spell allows one to know how much of their own energy is even needed for it. In rare cases, the lunar-arcane itself may be drained or, in some truly anomalous states, even be inert---"dead-magic zones," as they're known.
Finally, there are components. No arcane caster can ever overcome the material demands of their spells. A geomancy that requires certain stones will always take those stones, regardless of how perfect the caster is at casting it. The closest any arcanist can come to eschewing components is total mastery of a spell to the point of needing less materials to gather the lunar-arcane for it, but even then, some components will always be needed. This is the single greatest limit on arcane magic: the need of components as a medium to access the lunar-arcane.
I'm curious. Are spell intrinsic to the world i.e. the spell for fire is universal, or is it based on creation by an individual and then passed on to others?
Arcane spells are invented and shared; the other types of magic function differently. I'll clarify that in the article!