House Mercere is already using fertility magic (Mercury's Blessing, CrVi25, HoH:TL) and would undoubtedly use more if it came to it. OTOH, the Redcaps are going to asking the Gifted Merceres for that magic, so the question of "Who's available to train this Gifted child?" has to come up pretty quick. It sort of depends on who has access to this magic; if it's Order-wide, then pretty quickly magi will only be willing to train their own offspring (or descendants), because anytime they want an apprentice they can manufacture a Gifted child of their own bloodline. Only the old, infertile magi who never had children will adopt outside their bloodlines, and even that assumes they're an only child of an only child (etc, etc) going back so far they have no blood relations to tap into. And when that's the case, they'll tap the bloodlines of their friends. This is pretty much how all other apprenticeships in Mythic Europe operate - almost nobody takes in random children to train in their craft, it's all bloodlines and connections.
If the magic (say, Fertility Magic from Ancient Magic) is exclusive to one House, then the adoption system will remain in place. That one House will have more reliable offspring (as many as they wish to train) but there's going to be a pretty strong limit on growth. House Mercere is the only house where they really have to wait for an apprentice to become available (unless they go Illegitimate Lineage), and so they're the only house with a constraint on their growth. They'll probably go from 12 magi to 20+ in a couple decades, but I doubt any Gifted Mercere wants to continually be training apprentices.
One BIG difference will be magi will get married and/or have more children. If you know you can generate Gifted children on request, having descendants actually matters. The Order puts far, far more weight on your magical lineage (pater-filius) than your blood one because the blood one doesn't produce magi reliably. Once the blood lineage and magical lineage become one and the same, the idea of adopting outside your bloodline will fall into disfavor.
To get a real population explosion you'd need non-standard models of apprenticeship to happen. If you have six children and they all have the Gift, you can't train them in the normal fashion without severe difficulties. You can train them as a group with enough Parma Magica, Teaching and sticking to Abilities in the teaching season, but Arts are one-on-one, so teaching them to read and giving them free time to read books is the only way. You could well end up with a generation of well educated but magically weak magi, which would cause backlash into adopting the 'old ways' once more. You can generate a Gifted child when you want, but you only do so when you want to train an apprentice properly.
Echoing others, if there were a population explosion in a House, or the Order, a shift from apprenticeship to schools seems likely. Some things can only be taught one-on-one, but many things magi need to know can be taught to small groups, and don't have to be taught by magi.
Teaching Arts in person is really not the best way to get magically strong magi. Teach them Magic Theory, Finesse etc as a group, then have L6/Q21 summae for all Arts as a minimum and "magically weak magi" is NOT what you get. It´s the "magic school" style of training, and it can be made very effective even following RAW completely.
You don't have to teach them all at once though. And you can space them out --- so that the elder ones can teach the younger ones (kind of like large isolated families manage education in real life). Once the elder ones have a Score of 5 in an Art they are perfectly capable of teaching that to the younger ones. Or they can read books. The only thing that actually requires a season from a capable master is the Opening of the Arts. Reading books is pretty much the "standard model of apprenticeship".
For me, the big limit is the Longevity Ritual sterilising the magi parent (unless a variant that side-steps this is invented).
If you're using your older kids to help tutor the younger kids, and backing that up with L5/Q15 summae (or better), an apprentice who spends 2 seasons a year developing their arts can have 5s in everything in under 10 years.
Senior apprentices can be opening the arts of the junior ones just fine, if you're just looking for rapid expansion.
If you can generate Gifted individuals on demand without having to spend a season or two looking for them, you can go full Hogwarts scarily quickly.
Well, yes. But Scores of 5 in every Art is a "capable master" as far as Opening the Arts is concerned; assuming there are no supernatural abilities worth preserving.
My point was that an older apprentice with a Score of 5 in a single Art can teach that Art just fine to younger apprentices. The senior apprentice has a SQ of 9 (+/- whatever their Com + Teach Score is). It will take only two seasons of teaching to raise the younger apprentice to a Score 5 this way. Slower than a L5/Q15 summae, but still easily achievable to raise all scores to 5 within the 15 years of apprenticeship, assuming you have enough siblings ahead of you to teach you.
Also having, say, three elder brothers who each have a Score of 5 (or more) in 5 Arts is probably a lot more realistic than having all 15 L5/Q15 Art summae available; saga dependent, obviously.
The standard model of apprenticeship that the books use (and that's probably even practiced in Houses like Verditius and Tytalus, to name the two Houses I assume are the worst offenders) is being taught in the spring and then being a lab assistant (or doing scutwork like fixing Arcane Connections, extracting vis, and making charged items from lab texts) for three seasons. Most covenants don't have a full collection of Roots for the Arts, and apprentices are quite often put to use more for Magic Theory skill than for their proficiency in the Arts. (Plus, per Code, "give the kid a Root and leave him alone for a season" is not considered to count for the mandatory season of teaching.)
Now, will magi's children get a better deal than this? Possibly; a maga who loves her children might only expect one or two seasons of work every year (or none, though that will likely lead to an arrogant brat if you ask any priest...) and devote the rest to instruction (personal and otherwise). But these magi will be far stronger than corebook at-gauntlet magi. (Then again, I imagine that a lot of PC magi's apprentices will be exceptionally strong, if the PCs don't just treat them as lab slaves.)
You'd probably want a few experienced Magi around to run in-lab spell teaching - which is sadly only one-on-one, but labs can only be used one-on-one anyway. Hell, that's even more apt to Hogwarts, if some way can be found to generalize it.
In most cases a SQ of 3 + (Com+Teach), unless you can find a way to negate the Gift penalty from both the teaching student and the learning student. Extending Parma only works if the person who knows the ritual is going to be in the same room all day, at which point they're probably losing the benefits of having students teach each other unless they're also engaged in teaching in a pseudo-classroom study group environment.
Which is an important point, as Gifted children often have useful supernatural virtues you might not want to lose (or they might make Opening the Gift impossible at all for someone with In5 Vi5).
Don't forget the penalty for the Gift, which is another -3, so you're at SQ6, probably without much Teaching or Communication bonuses. There's no point in bothering, as almost any Summae will be of greater benefit than this. As others have noted, there's little reason to actually TEACH arts when there are L6 Q21 (or L5 Q15) Summae to be had. Also, it's generally considered to be the person opening the arts is the master.
Your all-Gifted offspring, unless Gentle-Gifted, will be an acrimonious lot. Even if you use your Parma to cover ALL of them during study sessions, they'll still hate each other because they aren't used to each other's Gifts yet and have built up the distrust while growing up. Throwing up a Parma doesn't make them forget past mistrust/hatred, after all. This kind of family could self-destruct fairly easily. Apprentices mostly don't hate their Pater because the Pater extends Parma over them from almost day one. Give children 7-8 years to build up hatred for each other and it'll last a lifetime.
If you're using Fertility Magic from Ancient Magic, the Unaffected by the Gift minor virtue (RoP:Magic) is pretty much a no-brainer to add in when you're custom-designing your offspring.
As for blood-children apprentices ending up being spoiled, it really depends. Some parents are quite happy to work their children like dogs and treat their children far worse than anyone. Some are extremely demanding and overbearing. In many ways it could be far worse than a regular 'adopted' apprentice, who is expected to clean and carry and assist in return for one season a year of training, but has no other great pressures put upon them.
Good point. Although, as you say if you are using Fertility Magic to inherit the Gift, you might as well inherit other useful Virtues too that negate this.
Perhaps unrealistic to have those available for all 15 Arts (your saga may vary). That is L6Q21*15 = 405 BP (L5Q15815 = 300 BP). That's a lot of covenant resources dedicated towards something that is "of no value" to characters who have finished their apprenticeship. It's 40-12% of the resources of a high power covenant.
Isn't it mentioned somewhere that someone whose child or parent is gifted may be unaffected by that specific gift?
Certainly it seems like someone who was born and raised alongside a gifted individual would count as "familiar" with it; it's hard to be more familiar with someone than having known them for your whole life.
I wish that meant something. But among the things I've learned, is that the library usually takes up by far the largest chunck of any given covenant's "point allowance", and that the power levels indicated in that box on p. 71 (of ArM5) gives ridiculously low levels of points.
Or to be more precise, once a covenant has been in play for a few years, maybe a decade (in game time), almost every covenant is 'High Power', if not 'Legendary Power', if the PCs bother to try to improve things, and you don't regularly torch the libraries.
I've lately come to the conclusion that the point (and vis) price for summae should probably have been based on level squared, not just the level. :-/
Off topic for the original thread, but it is worth remembering that the points-buy for a library doesn't represent the covenant's entire library, but rather what the (junior) PC magi have access to. The core rulebook actually mentions this as part of its description of examples.
Personally I use BPs only as a means of describing the starting state of the game. The moment play begins, BPs go out the window.
Its all connected- the price is based on the level because the resources to copy it are based on the level. Its the pricing for tracti which seem off to me, no level limit so they can be used by higher ability magi, they require a full season to copy regardless of the ability of the scribe (to be honest, that makes no sense to me), and yet they are only worth a couple of vis. I mean if your skill 6 scribe can copy 12 levels of summae worth 12 vis in a season, why would anyone copy a tractus, and yet it is vital to the advancement of the wealthiest magi that tracti be copied...
Going by the covenant build rules, yes. However, looked at practically, covenants would be dumb to not have them on hand. A full brace of these books lets you train to Open the Arts, and lets your apprentices raise their arts, as quickly as possible. Further, they're quick to write (one season on average) and can be managed by most middle aged-old specialists (Art 28) with +0 Com. The great writers of the order (Good Teacher, +3 Com) can bang them out at Art 16.
The covenant build rules don't cost out based on supply and demand, unfortunately. L6Q21 (39 points) books should be far rarer than than L5Q15 (30 points), but they only cost 33% more? This is (one reason) why I gave up on the Covenant BP system long ago.
Maybe, but a lot of the write-ups seem to imply that it isn't so. Gifted (especially blatantly Gifted) babies get abandoned in the woods. Gifted children are happily sold/given to magi who want them. And the rules for familiarity are all about getting to know someone and finding out they aren't so bad or can actually be trusted, and that's not exactly what I'd call the sibling experience (normal siblings squabble/compete without things like the Gift getting involved). Young children are often jealous of newborns who get all the attention. Imagine what a Gifted newborn would face as the Gift cranks that feeling up to 11.
There was a discussion on this forum, as I recall, that a mother may have more familiarity with her own child (I may have suggested that). It makes sense to me that a maga would have no issues with her child at least, as they would be under her Parma since before birth.
There is a Virtue insulating a mundane against the Gift, but it doesn't seem to be common.
However, there are certainly parents who are repelled by their own children, and stories of infant and child abandonment. I suspect reactions are not so clear as a game mechanic might make it seem.
I think that children would be used to the gift of their parents, as kingreaper suggested, but not necessarily the other way around, making both points of view actually compatible. After all, a child has known her gifted parent all her life, so I think she would be used to the parent's gift, not having known anything else to compare with. But the parent is not in the same position, as she was already a grown adult when the child was born.