With the basics of working spells laid out, we can flesh out more of the system to provide a stronger flavor. One of the ways I’m doing that is to vary how well the caster knows the spell being used, with familiarity having an effect on use.
Spell expertise
There are three levels of expertise when it comes to casting spells: researched spells, known spells, and mastered spells.
Researched spells are those spells the caster is working on, yet to finish. The caster has the research materials and has begun working out the magical patterns involved, so has a basic idea of how to form the spell. That said, the spell isn’t in final form and is unreliable and unpredictable. It likely requires extra time to cast and the caster has to check for miscasting it. A miscast brings fatigue and pyschic damage and the spell may have its effects twisted.
Known spells are those that have the final form worked out and the caster has a bit of familiarity with casting it. The spell still requires some extra time to work and has a slight chance of miscast. It’s full functional, just needs polish and practice.
Mastered spells are those that are well-rehearsed and readily cast. These are the spells that simply operate as described, with reliable results and no real chance of miscasting. The caster has used it enough times that they don’t have to spend much time thinking about how they’re doing it, just go about doing it.
Learning Spells
PCs begin with a mastered spell or two, plus a known spell. I expect developing spells to be a major part of playing a caster, so gaining additional spells is a game loop included during time spent in town. Magicians rarely find any materials that offer a spell in detail, mostly they get notes and have to work from what they already know and work out how to apply the information found in those notes to create a spell they can use. Even a spell found on a scroll doesn’t provide all of the information needed to master it, though it does help speed the process of developing a spell the caster can use.
So the wizard takes the information they’ve assembled and starts working out which magical structures and techniques are likely to work best for them when working magic that achieves the same ends. The vocabulary used, the meter of the lines, structure of the verse, what gestures are needed, what material components, and so on.
I expect PC casters will always have new spells in development, as finding spell descriptions complete with full instructions should be quite rare. The caster’s mentor can set up the PC with a couple of spells that are mastered at play start, and likely a few more that are known. Some materials to use when researching new spells is also believable, with letters of introduction or recommendation to assist in the new wizard gaining access to more materials.