There is a bar, which is almost certainly familiar to the reader.
In the bar is a person, also likely familiar, albeit surprising in this context.
"They are kind of creepy, though I think you're really overestimating how much information can be gotten that way - conscious thoughts in particular vary from person to person a lot more than most things do, so even if a mage has sat with a cooperative friend and put in the time to know that this particular combination of blue and red and the sound of wind chimes and the smell of orange peel means they've just decided to have a ham sandwich for lunch, that same combination of impressions probably won't mean anything even remotely similar for anyone else."
"There isn't a way to know what the mage is looking at from the outside - you can sometimes guess by body language, there's enough spatial awareness of that they'll tend to orient themselves toward whatever they're 'looking at', but that's not completely reliable and it's pretty subtle. Using the mage sense from a distance is possible but hard, and having something between the mage and the target makes it harder - distant, moving targets are basically impossible even with a clear line of sight due to steering problems, they're not going to be able to keep the field on the person as they move around. This does all assume human-like cognition, though - it's primarily attention-based, so a mage that was your kind of vampire would actually be pretty alarming in this regard."
"Learning to be a mage, yeah, anyone can do it, provided they can get a mage to teach them; what's involved with that varies from culture to culture, but it's generally considered a career, not something to dabble in - to give you an idea, a very large kobold tribe of 150 members would probably not have more than three mages, and might only have one. The actual process of learning involves another mage special ability, which is a limited touch-range telepathy: the teaching mage meditates, usually on a particular form of magic, and anyone who touches them while they're doing it becomes a mage and can see the magic form and learn a little bit about it. This world's magic doesn't allow for telepathy aside from that, but if another wold's telepathy is in use while a mage casts, anyone who's in the telepathic bond with them will become a mage and learn whatever magic form or forms they were using to the same level of detail that they know them, though they still have to go through the process of learning to cast in order to do that safely."
"It's also possible to learn magic directly from its source, but that's rare: The source of magic is naturally-occurring charged crystals, and touching one makes you a mage, instantly teaches you about casting to the point where you can do it as well as someone with 20 years' experience (which is actually a weird property of this world more than a magic thing, instantly learning skills can happen in other contexts too but can only happen to a given person once), and gives you perfect knowledge of one form of magic, possibly one that nobody's ever seen before. Most people don't even know that this is a thing that can happen; worldwide it happens maybe once every ten years or so."
"Mmhm! Okay, so, I have a bunch of questions, should I assume that your mysterious god-author powers include also being able to react to long strings of questions?"
"Yeah, I thought we might run into this, here." The bar top changes from woodgrained to a plain white screenlike surface, with a transcript of the discussion so far printed on it and automatically updating as the group talks.
"Let's see, then, string of questions. What are the forms of magic that there are? How do you learn these forms, in general? Is it possible to learn new magic without touching a mage or one of the crystals? How do you learn to cast things? How do these crystals come about, what are they charged with, where can you find them? What do you mean by weird property of this world? How do you learn other skills instantaneously? What is it that can only happen to a person once, learning a specific skill instantaneously or learning any skill instantaneously at all? And why are crystals so rare?"
"Reordering those a bit for ease of answering...
The world is actually loosely based on a video game - Dwarf Fortress, if you've heard of it, but I won't be surprised if you haven't, it's not very well known even here - and that's where the weird skill thing comes from. The original game doesn't have a magic system at all, but it has a mechanic where each dwarf in your fortress can (but only about 5 or 10 percent of them will), once in their life, go into what's called a strange mood and make an artifact, and at the end they get a major boost to the relevant item creation skill and also to their mood. The game is in beta; artifacts are eventually supposed to have magical properties, but in the current version they're just really fancy and indestructible, and that's what I'm going with for my world's version - the magic system I'm using makes magic items, we don't need two ways of doing that. From an in-person perspective, a standard strange mood is basically a week-long fugue state; once the person comes out of it they don't really remember what happened during that week, but the knowledge feels like they just naturally learned the skill, and the mood boost feels like justified pride at having made a really cool thing. I'm actually treating the ability to go into a strange mood as a property of natives of the world, so someone teleporting in from outside doesn't have the capacity and someone from this world teleporting out might have a strange mood while they're on their trip. If you try to do statistics to it, who it happens to and when it happens is completely random - it doesn't happen to babies but can happen to small children - but if someone has any experience with crafting, their artifact will be something that uses the general type of material that they usually craft with - metal or stone or cloth or what have you - and if they don't have crafting experience, it's always stone, wood, or bone.
The magic-related strange mood thing is different in that it's instantaneous and doesn't result in a physical item - I'm actually using 'magic form' as a concrete noun, here, and that's the created thing - but it's otherwise the same, including using up the person's capability to have a strange mood. Also, magic is an exception to the rule that if you have experience with a type of thing that it's possible to have a strange mood about, that determines what kind of thing you make - it's impossible to have a magic-related strange mood without a crystal; mages who get moods get them for the craft they have the next most experience with, or are treated as inexperienced if they don't have any mundane crafting experience.
The crystals are a naturally occurring thing - it's technically possible to make one, but there's no in-world way to see the background magical field you need to take into account, and anyway it takes hundreds or thousands of years for one to charge... I haven't determined a whole lot of detail about that, just that generally speaking the answer is 'no'. They do have to go a long time without being disturbed, so they're almost always found away from civilization, but it's not impossible that you'd find one in some ruins or even an abandoned place in the middle of a city if it's been abandoned long enough; this also explains why they're so rare and hard to find, though - you need just the right conditions for one to form in the first place, and those conditions have to be in a place that's protected from people and animals, and then whatever was protecting them has to not keep the person from finding the thing. And they're effectively single-use, too - if you touch a charged crystal and then leave it alone where it was, it'll eventually recharge but not within a humanlike lifetime; if you move it without touching it it'll retain its charge until it's touched, but moving a crystal from the situation that it charged in means it won't be able to charge there again at all unless you can put it back absolutely perfectly and not disturb anything nearby in the process.
An interesting thing about the charged crystals, while we're on the topic - once one is ready, it takes on a property related to the kind of magic it'll give, so for example the crystal that gave the original version of Lurker invisibility magic was invisible and she only knew it was there because she had a spell on her that let her see magical things, the one that gave the other version of Lurker her teleportation magic 'found' her rather than the other way around, that kind of thing.
Learning the forms uses that same touch-telepathy I was talking about - the way I'm modeling it is that each mage has a sort of metaphysical structure in their head for each form of magic that they know; it starts out very vague and undefined and unusable, but they can refine it by copying details that they see from another mage's copy via the telepathy. It's a lossy process, beyond a certain point - you can never get a better version of a form than your teacher's, unless you have more than one teacher who learned their versions of the same form from different people with different detail patterns, and copy bits of the same form from each of them, in which case you still can't get any details that one or the other doesn't have. Whether you can in theory get your form to be as good as your teacher's depends on how detailed their form is in the first place - there's a point past which the forms don't degrade unless someone just doesn't bother to learn the whole thing, but it's hard to get more detail than that and impossible to get a perfect copy above that level - the telepathy just doesn't let you see it in enough detail. The teacher's version being better does help, learning directly from someone who got their magic from a crystal helps significantly if you can put the time in to get everything you can from it, but there's always some loss in the process.
Without otherworldly magic, crystals and the mage-telepathy are the only ways of learning this magic. With otherworldly telepathy that has enough detail to it to allow communication and isn't strictly limited to something like a voice channel, if you're in telepathic contact with a mage who's using the mage-sense or meditating at all you become a mage, and if you're in telepathic contact with a mage who's actually casting a spell or meditating on a magic form, you get copies of the magic form or forms that they're using, at the same level of detail as the mage's. This is usually true even if the telepathy usually wouldn't allow for that - in particular it tends to be involuntary even if the telepathy usually only does voluntary communication, and it's especially likely to be involuntary on the mage's part. Other sorts of otherworldly magic, particularly anything like mind-reading, might be transmission vectors too, but I'd have to look at specific cases.
Learning to cast once you have a magic form is pretty intuitive - the form is a tool and a guide at the same time, once you have enough detail to use it at all you can figure out how just by looking at it - but there's a further wrinkle; there's a skill that's roughly equivalent to hand-eye coordination except purely cognitive that's involved in moving the things you see by mage-sense around to actually make the spell, and until a new mage gets good enough at that, their spells will inevitably go weird and then kill them, unless the spell is broken first. Breaking a spell that's on an object isn't hard - depending on how you cast the spell it can be as simple as picking the object up - but it's still something a new mage has to take into consideration: their spells will last a few days at most, and they have to be careful not to lose anything they've enspelled and to check them often enough, and they technically can but really shouldn't cast on people or valued animals during that period, since spells on living things can only be broken by the spellbearer's death. (Crystal-taught mages get to skip this part, it's included in the 'knowledge as if they'd been practicing for 20 years' thing. They don't automatically know that they can skip it, but if they're not familiar with mage training they probably don't know that there's a danger in the first place.)
I haven't put together a comprehensive list of forms, and I'm probably not going to - I want to leave the option open to add new forms if that's necessary for a particular character to be instantiated; it's entirely possible that the last practitioner of a particular form is living in some obscure village somewhere, or one of the animalperson species knows a form that nobody else does and the character can be a member of that species or do something to get them to teach it to them, or whatever, even without crystals involved. I can say some things about the kinds of forms that can and can't exist, but I think I need to talk about how spells themselves work first - we're missing a whole big chunk of how magic in this world works in practice, still."
"Where do the crystals come from? Are they just regular crystals that get charged up with magic, or do they just appear mysteriously, or what? After you've learnt magic from a teacher, can you then surpass them by practising? Why are spells cast on living things more permanent? Can you dispel something you cast on a living thing?"
"The crystals are just regular crystals, though I might fudge the world's geology a little to make it a bit less implausible for people to randomly find them - on the other hand, cut gems and things still count, so I might not need to.
This magic system doesn't have a way of dispelling magic at all, just breaking spells, and what happens with people and animals is that the soul 'learns' the spell and reasserts it any time it would break, otherwise with how spell breaking works you almost wouldn't be able to enspell living things at all. How spell breaking works is that when you're casting a spell, the first thing you do is define what you're casting on, which can be an object as we usually think about them but can also be part of an object or more than one object - also including liquids, though they don't hold spells well - and then if-and-when the 'object' is 'broken' into multiple parts, the spell breaks and stops existing - which is how 'you can break a spell on an object by picking it up if you cast right' works, 'casting right' means including a little bit of the table under the object in the spell, so picking it up disconnects it from that part. But if it was just using that rule, an enspelled person might be able to breathe without breaking the spell, if the mage was careful enough to not include the air in their lungs as part of what they were enspelling, but eventually they'd sweat enough to break it, or have a strand of hair fall out, or whatever.
For how good of a mage someone is, there's three factors, and you get the lowest common denominator of the first two and then whatever your aptitude is for the third one.
The first is what details your magic forms have, and for that you can't surpass the sum of your teachers - you can't research it or anything, what you can see from theirs is what you can get.
The second is the hand-eye coordination thing, which isn't hard enough to learn to be a major factor in most cases - it certainly can be for someone learning directly from a crystal-taught mage; if they can't manage fiddly little details they can't cast spells with effects that require them, but for someone a few steps down the teaching chain those details will be lost anyway and a couple years' practice will be enough to let them do anything they can do.
The third one is spell design, and this is where it's possible to do new things and surpass your teacher. The forms determine what you can do, but it's kind of like legos, or programming - you can just build from the directions, but you can also take the pieces that are on offer and put them together in new ways to make new things. Not very novel new things, you're not going to get a whole new magical effect under any circumstances, but the same old magical effect in a new context could still do something interesting - like, you could take the form that lets you create fluids and repurpose it from making self-filling water jugs to filling a dirigible with helium, if you had a sample of helium and an inventor-ish turn of mind, as a fairly dramatic example."
"I'm not sure I quite understand the hand-eye coordination thing? Why is it harder to learn for someone learning directly from a crystal-taught mage?" he asks, after he's finished catching up with the reading.
"It's like... okay, detail on a scale of one to ten - a crystal-taught mage gets a ten in hand-eye coordination and a ten in the level of detail of their magic form. Someone learning from a crystal-taught mage can get their copy of the magic form up to a nine, and then to use that nine as a nine, they also have to get their coordination up to a nine. Someone who's learning from a general mage who has the usual level of detail to their form can get that same level of detail on their own form, which is like a four, and they only have to get their coordination up to a four to use it to the fullest extent possible - as they get more practice their coordination will get up to a nine or ten level anyway, but they don't get any benefit from that because they don't have a form that's detailed enough to take advantage of it."
"Is there anything making sure magic doesn't just die out, other than luck and narrative causality?"
"Most cultures have a pretty steady supply of apprentice mages to learn the forms that are common to that culture, and those forms aren't in any more danger of being lost than any other form of knowledge. It's not particularly uncommon for newly discovered forms to fail to gain traction and die out, though, especially the ones that aren't useful by themselves - for example the 'detect magic' form can be combined with the 'emit light' form to give magic-vision - the emitted light is produced very dimly in front of the spellbearer's eyes - but it's useless without a second form to actually do something in response to the presence of magic."
"Oh, so for a low enough level of detail you don't lose any more when learning? I hadn't gotten that."
Nod. "Yeah, at a four out of ten or below it's possible to get all the detail that's on offer. It is still possible to lose detail over time - if, say, the last mage who knows a form has an apprentice and only manages to teach the apprentice up to a three before they die, then there's no way to get back to a four from there, that kind of thing."
"But that sounds exactly like the kind of thing that can easily be patched with the occasional crystal, I think."
"If someone gets a crystal with the same form and shares the knowledge, yep. Given a long enough time span, any form of magic can come back."
"That's an interesting system. Definitely better than the strictly personal, strictly unique kind we've got going on back in my place."