...and by HMRE he means HoH: TL, p. 109
Not really, but glad to know it can be found in other publications as well 
it is in the gruagachan chapter of HMRE, IIRC.
Possibly - I couldn't find it there though
I knew I had seen it there 
Not in the gruagach section, though.
HMRE p. 12
CHeers,
Xavi
It would suit the Diedne with the Nature Lore mystery, as well as a mystery that allows them to use Magic Lore + (effective) Nature Lore as a substitute for artes liberalis and philosophiae in ceremonial maguc. Effecttive Nature Lore is dependent on actually being in the area that the lore covers (-3 outside home region). This would explain why Druids valued their sacred groves... By performing their ceremonial magic in their own sacred groves they get a nice bonus...
And something else Id like to hear your oppinion on:
In our saga I am considering this flaw as a possible "house flaw" for the Diedne - in addition to the required "Dark Secret":
Oral Tradition
- Major Hermetic Flaw
You belong to a magical tradition that places little emphasis on books or written knowledge. Instead, magical knowledge is stored and communicated as an oral tradition of stories and teachings. In fact, your entire understanding of magic is based on a fluent description that integrates poorly with standard hermetic theory. This gives you several disadvantages when trying to study magic from written texts and when writing magical texts of your own. You are also at a disadvantage when trying to learn or teach magic to a person that is not a member of your oral tradition.
-3 study total when studying magical arts or arcane abilities from books.
-6 lab total when working from the lab text of another.
Writing books and clarifying your own lab texts for others to use requires twice the standard time. (E.g a tractatus takes two seasons to write).
-3 study total when learning magical arts or arcane abilities from a teacher outside your own tradition.
-3 study total when teaching magical arts or arcane abilities to a pupil outside your own tradition.
The implications of this:
- You can share magic with outsiders (teaching, learning, writing and studying books) up to the usual levels - it just takes longer time.
- It is not very cost-effective to share magic with anyone outside your tradition (thus another reason for Diedne seclusion)
- To reach high art-scores you would need a teacher from within the tradition - even as an experienced magus (thus explaining strong intra-house community)
- The other houses would regard the Diedne as closed and unwilling to share. And on the few ocasions where a Diedne would teach a non-Diedne (and vice versa), the other houses would regard the Diedne as poor students and teachers - perhabs one of the reasons their magic was held in low regard and underestimated by the other houses. In fact any Diedne could be as competent as a non-Diedne - but they would appear incompetent when sharing their knowledge with an outsider.
Unholy Threadmancy!
IMO, I'm not a fan of forced flaws (especially this one). Dark Secret and Diedne bother me, because it is a Story Flaw, which by RAW players should only have one, it's a Major flaw, and it doesn't count against flaw limits. I don't disagree that their Diedne heritage is a Dark Secret, but how many times are you going to play that story out? And if it gets discovered, why is it discovered with the PC, when there's an unbroken lineage of 200 years leading up to the canonical start time of sagas?
Instead of forcing flaws[1] onto players, I think it's important to have a huge discussion about how the troupe wants to handle a Diedne player. I think getting into that discussion will better highlight your reasons for wanting to add an additional penalty onto the Diedne Magic virtue. And at very least it gets discussed as to whether this is a flaw that counts against virtues and/or whether Dark Story should count against virtues, or at least another story flaw be chosen.
[1] I also have a problem with Mercurian and the ceremonial magic requirement, because in many ways that is a huge flaw, but that is beyond the scope of the discussion, except so far as to say that I am consistent with my dislike for virtues that include flaws for "free."
I am not a fan of forced flaws either... so I suggest that we leave the "Dark Secret" story-flaw out of the discussion for now - if thats ok with you?
But what I am trying to do here is to use the Ex Miscellanea template (1 minor virtue, 1 major virtue, 1 major flaw) to construct a plausible Diedne-set of hermetic house-virtues and -flaws. These are off course in addition to the usual 10 points of virtues and flaws...
- for the minor hermetic virtue I would leave it open - allowing for some variance within a large and diverse house like Diedne.
- Diedne magic would be the major hermetic virtue
- Oral Tradition would be the major hermetic flaw
I am aiming at something that would describe the Diednes unique heritage and also explain some of their alienation within the Order of Hermes.
At the same time, the major hermetic flaw couldnt plausibly be something that severely limited their offensive or defensive capabilities - since they were able to hold their own for such a long time during the Schism-war.
I would contend that if all Diedne shared the same Hermetic Flaw, it's an additional way to identify a Diedne magus, and would suggest that there should be very, very few.
Their "alienation" within the order is forced, because they were renounced as a House, and that still holds, based on the description of the virtue in the book. Judging your flaw strictly on the mechanics, first, you're incorporating about 3 minor flaws into one "major" flaw, which upon a first blush appears fair. But stacking them together is pretty tough. -3 Study Total is essentially Poor Student, in fact with all of them combined, it's effectively poor student, but circumscribed by the possibility that they could learn from within their own tradition better. -6 lab total from texts is Weak Scholar. The writing one may or may not be a flaw at all, if a player never writes, then it isn't a flaw, and if they have this flaw, what is their incentive to write?
On the story aspects, this doesn't really lend itself to Diedne line integrating and hiding itself within a House. These magi will become cookie-cutter, and easily identifiable. If magi are always going back to sacred groves, because that's where they learn best, or they seem to work with the same set of people all the time, and don't work well with others, and that's identified, then boom, hey, there's a nest of Diedne, wipe 'em out. Stating it another way, when you force a mechanical flaw onto players like this, you're also creating a marker that magi (certainly all Quesitores and possibly hoplites) of the Order should know to be on the lookout for. Such a group wouldn't last long, IMO.
Addressing the parenthetical note in your second implication of your first post, Diedne aren't secluded. They are hidden in plain sight, and work very hard to stay hidden and blend in as much as possible. Addressing your contention that Diedne are alienated from the Order in your second post, that's plainly wrong. They are renounced/hunted. Their existence is not to be allowed. Now, if you're creating a nest of Diedne magi that have been hidden from the Order, and come out to extract their revenge, what you are proposing is fine.
If it is for a PC, I have to ask what PC is going to want to play with these additional restrictions? What does the player get out of this. Diedne weren't an ex Misc tradition, they were a fully integrated tradition not of Latin origin, like Bjornaer and Merinita. Those houses do not have forced flaws. ex Misc have forced flaws, because often times their virtues and flaw make up has a fair number of supernatural components giving them their flavor, and their integration into Hermetic theory isn't complete, either because the tradition doesn't desire it, or they haven't been able to complete the research.
To me, House Diedne were, like House Verditius, a house with a minor virtue with major downside.
House Verditius and casting tools. House Diedne and a difficulty with formulaic and ritual spells.
Diedne Magic doesn't have the flaw that was built into Diedne's original Minor Virtue form for one simple reason: Only those members of the house who managed to overcome the flaw could hide within the rest of the order.
I also suspect that Diedne had Fertility Rituals as a mystery, hence their high magical population (and the general highly gifted population in the british isles). They generated gifted children deliberately.
I don't consider casting tools a major downside. Meanwhile, they are laughing all the way to Harco (the bank) with all the vis they charge for their items...
Well, I'm pretty sure the Verditius Magic would be a major virtue without it. I do agree, Verditius Magic is probably worth more than a minor, even with the flaw, but the principle stands 
Did I mention that Sub Rosa issue 13 is a House Diedne special?
Major virtues don't become minor because of the flaws associated with them. Were that the case Mercurian Magic would be a minor virtue!
I can't be certain why all the MCs have minor virtues as their House virtues, except of course, all Houses have minors as their House virtues, and so I suppose it was that sense of "balance." But on its face, I don't consider casting tools a "flaw." I don't often, in fact I have never, taken them away from someone. I can reasonably assume a character will keep his casting tools and the grog who carries them in his pack close at hand, or he keeps said tools on his person. If, as Spontaneous Casting Tools from HoH:Societatas suggests, that there are 15 necessary tools, one for each Art, having them on a necklace isn't impossible.
It depends on how powerful it is before you add the flaw. Sometimes the flaw would just move them from "Impossibly powerful virtue" to "major virtue". I'm not sure how well balanced the system actually is, but that seems to be the principle at work.
There are many reasonable situations in which that might not be sufficient. Someone with a low level Perdo X spell could destroy them. A paranoid individual might make you leave them behind. etc.
Sure, they're not a flaw if you're running and choose not to make them one, but they're clearly intended to be a flaw. They're akin to a necessary condition.
The impression I get is that those 15 are only for spontaneous. Each individual formulaic spell gets a casting tool. If there's just 15, Enchanted Casting Tools doesn't really seem to work.
I don't consider Mercurian to be all that powerful under RAW. Can't use it to cast the Aegis, because you need a Communion which negates the major benefit of having a Mercurian cast it, unless all the participants are Mercurian, and how often does that happen? And then just how often are you casting rituals anyway? Really?
And I had this discussion elsewhere and I left out Verditius, so did the other part[y/ies], when discussing virtues that have built in flaws, or required flaws. Diedne is the only virtue that has a built in flaw that is a major one, counts for 0 points in Flaws, and essentially prevents a player from taking another story flaw, since, as a rule, players should only have one. Of course should is <> must.
Sure they are, but in reality, Necessary conditions and Restrictions are relatively easy to work around. Not all Virtues and Flaws are created equal. Magic Addiction, for example is a much more potent Flaw than either Necessary Condition or Restriction, because it affects nearly every spell, all nearly the time[1], and there's always the chance for botching. Blatant Gift may or may not be bad, depending on how well a troupe actually RPs the Gift. Rigid Magic and Unstructured Caster are both pretty powerful flaws, all but precluding a class of spells for each group. This is one reason why the concept is important, why the discussion of story, and how the saga is going to work, so that the player can play a character that's going to be fun. In a high adventure combat heavy saga, is Slow Caster a minor or a Major virtue?
I can go either way on that interpretation. If you need casting tools for spontaneous spells, representing every Art, why not casting tools for every Art applying to formulaic spells. Unless, and I might have missed it, each spell has its own unique casting tool. Even still, this is where a Verditius will rely upon his Wand of PoF or other suitable destructive combat spell enchanted into an item, than relying upon vagaries formulaic magic.
[1] The decision of what is a stress die is largely in the hands of an SG. And even the RAW can really mess with someone with this flaw. Take a spell like the Leap of Homecoming, a 35th level spell, cast it under stress, with a magus who can barely cast it, either due to requisites or just raw ReCo CS and arriving naked, his EF to check for continuing to cast is either 17 or 18, probably 18. So he's almost always going to be casting spells until he can gain control, which might be a couple of rounds,and he might be 1 or 4 fatigue levels down.
Edit: added nearly to the description of when Magic Addiction applies, and the footnote.
Just to clarify - What I am aiming for, is a description of House Diedne PRIOR to the Schism War.
If I can get a plausible impression of the House pre Schism - then I can continue to consider the implications for any "survivors" in the "present day" (1220 
)
- some Diedne may indeed be hiding in plain sight. And one of the implications of the "Oral Tradition" flaw is that it need not be overt. If you were a lone surviving Diedne you could fit into a another house without gaining the attention of Quasitores or the Vexillation of the Burning Acorn... You might get a reputation for being a somewhat slow learner though... but that is neither a high nor a low crime in the Order...
That is a quite an interesting observation. I allwas had the impression that according to Hermetic history the Diedne were not fully integrated...
Well, there is nothing canonical about House Diedne, except what has been written in the ArM5 book. So, any opinions are likely to vary wildly.
My question is why are you trying to do get an idea of what the House was like before the schism? What problem will it solve for you, that you currently have? Again, repeating my comment above, without answering those questions you're going to get a lot of different opinions.
There has been a bit about the Diedne spread around the supplements in this edition. Here's a thread from 2007 that gathers a good number of the statements about the house together
@Jonathan:
Well, its not so much about solving a problem... Its more about exploring the magical lineage of celtic magic - starting with pre-Diedne Druidism and ending with any surviving members of that lineage today.
- what would be the defining characteristics of such a non-roman lineage?
- what were their role in Celtic society and how does that reflect in their magic?
- what would change as the magical tradition got involved with the Order?
- what would change after the Schism war?
- what could endure over time?
Of course I could have started with questions of balance and gameplay and then working backwards in time from there...
... but I must admit that I really enjoy this exercise into fictitional magical genealogy...
EDIT:
@Erik: Thanks for that link - very interesting argument unfolding in that thread
@Mark: Ill be looking forward to the 13th Subrosa then
I've only skimmed that, but, as best I can tell, it doesn't address any of the mechanical issues related to how the House functioned. So, I was imprecise, but the gist was correct, in that I was referencing mechanics, which is what John the Arms was looking for.