Hey there, I've been obsessed with world building and magic systems for years and I have one in particular that I've mostly fleshed out but will probably never do anything with. I would love to see it used though so I thought it might be cool to make a thread for people to describe magic systems that they're cool with other people using. Here's my notes on my magic system, sorry for all the "basically"s:

Basically I’d have two systems of runes based on what you need with maybe a third pseudo-system. One would be like the phonetic alphabet but with different symbols and with spoken words being a unique Romance language such that people don’t accidentally say stuff or write something that will kill them. This is useful for more versatile runic circles and arrays since you can basically just write what you want to happen but it’s significantly more time and space consuming than the second one which is more like Asian written script with each symbol meaning one or more whole concepts or conjunctions but it can be harder to get a specific new effect since you have to figure out how to formulate the commands instead of just writing down what it’s supposed to do. The third bit is more like a personal shorthand where you just make one rune that completes an effect you’re incredibly familiar with.

As for their uses basically again, two ways and a hybrid. The first way is anchoring effects for stuff like wards and enchantments in which case you basically just write what the enchantment or ward does on whatever you’re enchanting or warding. If you’re warding a general area instead of a castle or something then circles are best but for enchanting and warding physical things it’s better to mark the runes directly onto the surface of whatever you’re ensorcelling. The second is for enhancing spellcasting. In this case circles are always better. Preferably drawn on or carved into the ground around the Caster but projected by some illusion in front of them also works, if less effectively. Having it in a book or something is ok but more related to the third thing which is making foci. Like spell circles, foci increase the casting ability of a mage but they’re less powerful than the carved ones because they’re moble and also generally smaller. They’re still better than an equivalently skilled illusion circle but those are useful for something I’ll get to in a bit.

Enhancement runes for both circles and foci differ in two ways. Focus and specificity. Focus is whether the runes are supposed to increase power, control or both. Specificity is what it sounds like. If it’s more specific it’s more effective. This is generally in four tiers, General, School, Class and Spell. So a General focus would just help you be better at all magic, a School focus would make you even better at creation type magic, a Class focus would make you really good at healing spells and a Spell focus would make you fucking fantastic and Bromir’s Healing Breath. Foci tend to be School at the most specific because they’re permanent enough to be a pain in the ass to change but their purpose is to make the user more capable which requires at least some versatility so a more specific illusion can be more useful, especially in conjunction with a focus.

In addition to specificity, the medium and method matter for effectiveness. In general, carving or etching is better than writing on the surface, more valuable is better than less, durability is good, and more inherent magic is better than less, though that can be the opposite in some cases such as using sanctified silver to fill in the carvings in your demon summoning circle but blood is as close to unaligned as you can get without some really rare and/or expensive materials like orichalcum as long as it’s yours. This is why illusion circles suck. It’s not at all permanent, it’s somewhat magic but specifically aligned to illusion and not too powerful since you don’t want to waste energy on a quick setup and it’s not actually on or in a medium of any sort.

Runes are basically the written form of the First Tongue, which is the language that spirits and gods naturally know. One of the properties of the First Tongue is that everyone understands it as if it were their first language. However, unlike Tongues, the spell that crudely imitates the effect it's generally not a good idea for anyone but gods and spirits to use it as an actual method of communication since it is the best language for shaping mana and if you haven't mastered it you can often accidentally create magical effects. This is also why people use Latin a lot, older languages are closer to the First Tongue and without a god or spirit who actually bothered to learn a crude language to teach you it's almost impossible to learn the First Tongue.

I know the verbal aspect of the system isn't super fleshed out but I can't think of anything more specific than general Eragon rules. Plus, if you decide to have this magic system restricted to Unicorns than that doesn't really matter anyway. It was actually originally designed for a story about an Earth Pony mage that mutated to be something totally different that can't really use this system to its fullest potential.