I wonder if there is any spell guidelines for effect that would induce knowledge in or steal knowledge from an individual. I do not remember having found something similar in the supplements, but I might have missed it.
I have thought about something like this :
base effect Creo Mentem 10 : Infuse the target with a knowledge the caster possesses. The target receives the knowledge with a score of 1. Each additionnal magnitude adds 1 to this score. This cannot be superior to the caster's score. Physical abilities can be induced with a Corpus requisite, supernatural need Vim. Must be a ritual.
Creo Mentem 5 "create a memory in a person's mind" (ArM5 p 148). I assumed that creating memories of a knowledge is a bit more intricate so base effect is one magnitude higher.
base effect Intellego Mentem 25 : Investigate a knowledge possessed by an individual. The caster receives the target's ability with an equivalent score. Same requirements as above. Must be a ritual.
Intellego Mentem 25 "learn all the information you wish from a person's mind", so would theoretically allows the magus to learn all the knowledge the target possesses. But learning an ability this way is more than simply searching the target's mind : the caster must assimilate and shape the knowledge received to fit his own mind (and body if it is a physical ability), just like an accelerated training. This requires time and that is why it needs a ceremonial casting. Ritual because the effect is very powerful.
Societates claims this is impossible (under Jerbiton, when it discusses memories). While it isn't against any particular law of magic per se, it is against the spirit of the laws - you can't gain Virtues, scores in Abilities, and so on through magic, or it would be too easy!
Personally, I'd add another law of magic - the Law of Experience: magic cannot create or transfer the fruits of experience.
What Yair says, mostly because it sounds like a quick way to study to me.
But if you really want to introduce it, here's some house rules we put on InMe'ing all of someones memories.
You can only hold 1 person's memories per point of your own intelligence (as soon as you intellego your 4th mind, you loose the 1st)
You need to cast a good recollection of memories spell on yourself if you wish to look through those memories for details
It inflicts a warping point for strong magic effects on the target
So you can think of loads of warping for the caster if he wants to mnemonically enhance himself. (because it would be a nice concept from time to time, it's just so prone to abuse)
I can image using a book someone has writen as an AC to that persons mind, allowing you to store the books info instantly. You haven't actually learned from it, but you can now access the book at any time. Or the same for direct info from a teacher. (but this should be limited somehow)
This is covered in the Jeribiton chapter of HoH:S, and basically the idea is that Hermetic magic could theoretically do this, but currently can't manage it properly. Not because there's a Law against it (it can get close, letting you have the steps of a single dance, for example), but it just can't get the Levels, or perhaps Finesse Rolls high enough yet. If, in time, the levels or Finesse rolls required are lowered by original research, magi may eventually just imprint their apprentices using the ghosts of dead magi as templates. Well, that happenend in one of my campaigns once. You had all of these pubescent archmagi and a group of olde, kaer magi trying to work out if this had been the best of ideas in the first place, or maybe in appreticeship at 7 was no longer the best of ideas.
I too agree that it might challenge game balance. And if need be I think the present Limits can already account for why it isnt possible (maybe somewhere inbetween Creation and Energy).
If you want to introduce I'd go for a much coveted Mystery - a treasure trove of knowledge... and make it the focus of a story arc.
We had some diabolist we captured and one of the magi wanted to suck them dry before they were executed, this is what we came up with based on the the Intellego mentem spell that allows you to "know everything a person knows". The following may have been fine tuned but I couldn't find more current notes on it....
It could only be used once on a target, took a whole season(is lab work not spell), tended to have some big side effects like possesion, that needed to be solved. Obviously against the code, hence the need for a target that has been marched. Doesn't work with knowledge you don't already have an idea about (can't use it to learn mysteries) and of course gives major warping (to you and the target) just about garenteeing twilight. In general it has so many drawbacks that it's not nessacary to make the magi learn a mystery.
You can always "destroy" knowledge- that is easy using PeMe.
"Draining" knowledge could be simulated with an In(Pe)Me, but, as discussed above, the Intellego aspect would not, should not permanantly give any "Ability" to a recipient. It's like going into a library and reading a book in an afternoon (in game or in RL) - you know "some stuff" that you didn't before, but that's not broad enough, nor long-lasting enough, to actually improve "an ability", in game terms.
Of course, a non-Hermetic NPC might have developed something, and that could be a huge threat to the Order, and/or a greatly desired secret. Can it be won before House Flambeau marches him to his doom? (I'd bet... no. But it'll be fun watching them try.)
OOOOOH, knowledge draining demons, always a great idea!
In the ArM standard system it would probably be a highlevel power, so the penetration is close to nothing. This would mean that grogs and townsmen can be drained of information about the covenant. Dangerous situation for the magi: knowledge about them gets to where it shouldn't be, townfolk goes insane (let's blame the magi for that) and the real important magus characters aren't drained (since they have parma).
Great story opportunity IMO. (since I don't like the idea of sucking the memories out of a player character, it simply ruins the game to easily)
Thinks he hears a big sucking noise and suddenly finds himself utterly confused about what this place is, nd what's with this Ars Magica-thingy at all?
NB - I also like the idea of brain-sucking infernalists... isnt that a terror on the Order I wouldnt know what would be!
Thanks for the reference. As I thought, I had missed it. I didn't plan to introduce this in my saga. Was just curious about what could be done.
Actually, I didn't thought of a possibility for such an effect to be permanent, even with a momentary ritual. Knowledge gained in this way, having not been assimilated naturally by the magus, should be volatile and hard to "fix", perhaps in the same way it is difficult for an immortal magi to fix his experience points.
I like this idea of introducing a specific laboratory activity to fix stolen knowledge. Also, drawbacks like risk of possession seems indeed sympathetic to that kind of magic.
Maybe the magus could also gain more than desired when extracting knowledge from an unwilling mind ? Abilities are not just flat knowledge. They are experience in all means, linked to the story and life of an individual, so a magus trying to extract them could also gain some personnality flaw or flaws related to the target's mind or the ability extracted.
All in all, it would probably be more interesting to learn from a book or a teacher, but this effect could be useful to acces to a very uncommon knowledge coming from a very unwilling mind.
Sounds interesting. It is another way to bring limits to that kind of effect. But the limit on memory seems strange to me. Theoretically, it is pretty simple for a magus to create "empty memory space" in his mind, so the first limit, while interesting, seems not very justified. Also, perhaps the ability "Art of memory" could be of help.
That being said, the "book view" is nice and fits well in the concept while bringing good limits, which are fully compatible with what is mentionned below.
Actually, having these in mind, I don't see a need for a new limit on hermetic magic, Extending the rules to cover this kind of effect and bring to it meaningful and interesting limits seems enough to me. There may remain some power gaming issues in these, but this is the case for many aspect of hermetic magic. Momentary CrCo, CrMe rituals to permanently increase characteristics are just an example.
I didn't plan to introduce this in my saga. Was just curious about what could be done.