This is where I'll be posting any house rules and interpretations that might be relevant.
Arcane Connections, Fixing
Ars Magica Books Usable in Character Generation
Books: Reading and Writing (clarification)
Borked Spells (spells that I've come across, in either the books or on various websites such as The Net Wizard's Grimoire, where the level has been miscalculated)
Order of Hermes Rolls
Spell Mastery Options
Virtues & Flaws: New or Modified
I'm pretty sure this has been addressed in at least one of the supplements, but just for clarification if nothing else:
You need to have a Language Score of 4 and an Artes Liberales Score (with literacy in the script in question) to be able to read a book in a given language and gain benefit (i.e. get xp from it); with a Language of 3 or less, you can still read it (as long as you have the Language and the Artes Liberales), but you don't understand it well enough to get the benefit. Most books in the Order are in Latin, but there are likely to be a few books floating around the Tribunal in Scots Gaelic.
[strike]You must have a raw Language Ability score of 5 to be able to write anything with a Source Quality (such as summae, tractatus, letters for the Correspondence rules somewhere). To simply write letters or whatever, you simply need the Artes Liberales and literacy in the appropriate script. Note, however, that with a Language of 1, it's going to wind up looking like the letter I just got from my six-year-old cousin.[/strike]
After some thought, reading on the forums, and looking over the published characters in the Main Rule Book as well as the supplements, I have come to the decision that using a Specialization in Latin (or another appropriate language) will allow the character to study from, or write, a book or other text. This stems, in part, from my observation that practically none of the published characters (including members of House Bonisagus) would be able to write books if this were not the case, and at least a couple are of an age and description that indicated that they had done so.
The Order doesn't use the Age of Aries calendar system. The calendars in use are the Christian, the Jewish, and the Muslim as appropriate, but almost universally the Christian calendar.
Also, the saga year begins in spring. Thus, 1222 consists of Spring, Summer, Fall/Autumn, then Winter.
It makes no sense to me that you should be able to take Multiple Casting once, take like four other various Mastery options for the same spell, and be able to cast six copies of the spell. So, going through the Spell Mastery options listed on the Atlas .pdf download, the following options may all be taken multiple times with the following benefits:
Apotropaic Mastery allows the magus to add his (Apotropaic Mastery) x Hierarchy score to the level of effect of the mastered spell.
Imperturbable Casting allows the magus to add his Imperturbable Casting score to all Concentration rolls related to the spell.
Lab Mastery allows the maga to add her levels of Lab Mastery to her Lab Total when designing effects that are similar.
Multiple Casting allows the maga to cast one additional copy of a spell per Multi-Cast slot.
Obfuscated Casting allows the magus to add his levels of this ability to the Ease Factor.
Penetration adds the number of Penetration abilities to her Penetration Ability for determining her Penetration Bonus.
Precise Casting, Quick Casting, and Quiet Casting add their benefits for each time the particular ability is taken, not per overall levels of Mastery.
Rebuttal adds three times the caster's levels with Rebuttal to the effective level of the Vim spell when determining if it can change or control the foreign magic.
Unraveling allows the magus to add three times his Unraveling to the effective level of the Perdo Vim spell when determining if it can destroy the targeted spell.
Correcting spells from the books or websites that are calculated incorrectly or are otherwise just wrong. Listed alphabetically.
Naked Man Weaving: The spell adds an unnecessary magnitude for size. Everything else in the design calculations is correct, so the Spell Level is actually 10, not 15.
Trackless Step (Ar5, p. 155): This spell uses a fictitious Base Level (4). Upon review, the spell construction should be Base 2 ("Control or move dirt in a slightly unnatural fashion"), +1 Touch, +1 Concentration, +1 for Stone or Glass (as the spell also controls pebbles, scree, etc.). Final spell level should be 5, not 10.
Selkie Blood is a new type of Faerie Blood which (in addition to the normal benefits of all Faerie Blood types) gives +3 resistance to cold (normal and magic) and a +1 to Swim.
A brief explanation on how I plan on doing the stories.
I am going to shamelessly swipe the basic premise of Jonathan.Link's system from his In the Ruins of Bibracte campaign. Each season will be numbered (such as 1222.2 for Summer 1222, or 1223.1 for Spring 1223). Each magus or companion will be featured in a randomly rotating season. For example, Halie is featured in the Summer 1222 season, Nevin in Fall 1222, and Siobhan in Winter 1222. With the characters that we have now, that means that each character should be featured once every two years.
That doesn't mean that no one else's magus/companion will be allowed to take part in those stories; it just means that that story will feature that character in some way (most likely, using their Story flaw).
I will also be instituting an annual rp thread for characters to interact outside the seasonal threads, because that makes for some awesome stuff sometimes.
Also, you may notice that I tend to use the words saga and campaign interchangeably (but preferring the latter). I'm old-school, that's how I roll.
It takes one week for every step removed from Indefinite that the Arcane Connection is at the beginning, and you must have a ReVi lab total of three times the number of steps. Thus, to take a bottle of water from a moving stream and use it to fix an AC to the stream would take six weeks and you must have a ReVi lab total of 18. To fix an Arcane Connection from a strand of Caoimhe's hair would take three weeks and require an ReVi LT of 9. As per Rules As Written, once you begin the process of fixing the Arcane Connection, it does not decay so long as you continue the process. If, for whatever reason, the process is interrupted or suspended, then the Arcane Connection begins to decay again. (This should only be a problem for those Arcane Connections that last hours or days.)
It would still take one pawn of Vim vis.
Character creation uses the rules as written, in the main rule book (Detailed Character Creation, pp. 28-33). This includes the section on p. 32 about post-gauntlet advancement.
A magus may be initiated into one level of a mystery cult or secret organization (e.g. Theriomorphy or Path of Seeming). Such initiation counts as a "season that your magus spends working on a lab project," (p. 32, third column, second paragraph below the list of assumed situations for advancement), and may take additional seasons based on the requirements for the cult; this will be determined on a case-by-case basis.
Any virtues, flaws, abilities, spells, etc. found in the main rule book and the three Houses of Hermes books are automatically approved.
Anything from any of the books that I have will probably be allowed, on a case-by-case basis.
Anything from a book that I don't have will probably be denied.
Not so much a "House Rule" as something I use to see how much a character knows about another character. I don't know how well they've been tested, and if they turn out to be unbalancing or don't work right, I may wind up tossing them.