In Ars Magica, Covenants, they claim that most "standard" summa as distributed through the Order of Hermes have a quality of 28-level.

Despite spending 6 hours trying to understand the math (with errata), I was not able to achieve 28-level for Arts or Abilities in any "common" sense.

What is the exact process for producing a summa with a quality of 28-level in a standard and reproducable way with a "normal" summer or autumn magi?

For purposes of this example, let us assume a magi writes a level 15 summae on the art of Mentem. How does she achieve a quality of 13 within her standard 120-160 year lifespan?

Given: An autumn magi with a communications of 4 (magically enhanced from 0), a score in Mentem of 21 (equivalent to an ability of 10, which takes a lifetime of learning and practice. We can say she has spent 28 seasons over her 80 years simply studying from vis or its equivalent.) Level 21 is considered to be exceptional, but not legendary. An equivalent technique would allow her to routinely cast level 40 and 50 rituals, explaining the communications of 4 (and it's commensurate warping.)

Thus, she can make, as per page 88 in Covenants and per page 165 in the core book, a summa of level 10.

The core book asserts that this summa's base quality is communications+6, or 10.

Page 88 asserts:

Author’s Communication + 3 +1 for skilled scribe +1 for skilled binder + 1 for skilled illuminator + 3 (or less) due to mystical resonance + bonuses due to Virtues + bonus for writing to level less than half of Art score.

The autumn covenant absolutely has skiled covenfolk, so she has 4+3+1*3.

The book is bound in expensive and resonant materials, resonance +1, has story-related materials incorporated in, resonance +1, and has been opened to enchantment, allowing for a 3 year clarification process for a total of +3.

Once the materials of the book have been transubstantiated into more magically appropriate materials via its process of clarification, the book has a quality of 4+3+1*3+3 = 13, is considered extremely valuable, and cannot be taken out of a magical aura. Level+quality is still 23.

We can assert that this obsessive mentum magus has had a colleague with a communications score of 5 gloss her book, for a quality total of 14. She cannot turn the work into an inspeximus, as her mentem has not substantially increased during the time of clairification. Specifically, her mentem would have had to increase by 3 points, or 69 xp in that time.

And that leaves me with a summa on the art of mentem, prepared by a maga in her prime, with a quality of 14 and a level of 10.

And we still haven't met the minimum level for trading sound books, despite having invested seriously non-trivial amounts of time and resources into the book, time and resources that make the book functionally ineligible for trade: the very purpose for the book's creation.

  • \$\begingroup\$ Remember, summa of a given quality level being common doesn't mean that authors capable of creating those summa are common - on the contrary, they're likely to have been the stand-out few whose works were so excellent that they they were widely distributed. As a result, the order's greatest authors are most likely to be experts, specialists in their field with an extended lifetime of experience behind them - not just 'ordinary' summer and autumn magi. \$\endgroup\$
    – GMJoe
    Commented Mar 14, 2013 at 2:45
  • \$\begingroup\$ Which is why I'm not asking about exceptional summae that are not the focus of this question. I am interested in the "sound" summae that are good but not incredible examples of their kind. Of course, if you want to explain how an exceptional summae can have a quality of 31-level to 35-level, I'm happy to hear that too. But still, even for any quality book, the numbers simply don't add up for me. There are ten points of quality that I simply cannot find. \$\endgroup\$ Commented Mar 14, 2013 at 2:48
  • \$\begingroup\$ I don't have a copy of Covenants, so what is the minimum for trading? Also, I've updated my answer with one option inspired by earlier editions. \$\endgroup\$
    – Mark Booth
    Commented Mar 20, 2013 at 1:58
  • 1
    \$\begingroup\$ Y'know, with the quality 14 level 10 summa produced in your example, a magus could reach an art score of 10 in only four years of intensive study- An impressive head start on the score required to write a similar book of their own. Yes, the next 11 will be harder to come by, but it's still faster than studying from vis. What I mean to say is that your calculation for how long it takes to earn an art score sufficient to write a good summa doesn't take into account the availability of the summa you're asking about. \$\endgroup\$
    – GMJoe
    Commented Mar 20, 2013 at 6:40

4 Answers 4


I think you underestimate the level of art scores achievable by magi in this game. I'll give a back of the napkin style calculation of where I expect them to be.

For these “standard of the order” books we’d expect them to be written by notable experts in the field. With standard longevity rituals using optimized labs, assistance in the laboratory, someone who puts a reasonable amount of emphasis on the relevant arts for longevity rituals and an applicable virtue or two (not necessarily something as powerful as minor magical focus aging, but an affinity or two puissant art/abilities) you can make a very impressive longevity ritual that can easily (especially when you consider the additional effects of a strong bronze cord, a living conditions bonus and a bonus from an attendant physician) allow a magus to live more than 130 years past their gauntlet. Longer is certainly doable but gauntlet + 130 is sufficient and doesn’t make us assume that our author is writing his masterpiece on his deathbed.

So 130 years past gauntlet , let’s see what sort of an art score that gives us: From apprenticeship, I’ll assume 20 xp and an affinity in the art (I don’t think that affinity in the art is such a big assumption for a notable expert) so 30 xp.

The magus then has 520 seasons in his 130 years. In my experience magi typically spend a bit more than half of their seasons in study, I’ll be conservative and assume that the magus only spends 50% of his seasons studying. I think that if they really care about their art (and magical focuses in fifth edition make caring about a single art a much more reasonable proposition than in previous editions) that spending one fifth of their seasons of study working on their art is reasonable so 52 seasons. A mean quality of 8 for materials that they’ve studied from is (IMO) a conservative guess. With their affinity this gives them an additional 624 xp

Finally I’ll look at exposure xp. When the character is in the lab or doing non adventure work they’ll get exposure xp. Lets assume this happens about one fifth of all seasons (once again, pretty conservative). So 104 seasons, I’d guess that they’d put some exposure xp into their favorite art about one third of the time that they get exposure xp. This gives us 35 seasons at 3 xp a season (2 +1 for affinity) gives our author an additional 105 xp.

A final total of 749 xp in the art. This gives us an art score of 38 which is going to be adequate to write the books that you’re looking at.

  • \$\begingroup\$ And Now I see you were asking about sound summa rather than "roots" of the arts. Still, I think that elders with art levels in the mid to upper thirties is reasonable. The core book says that the max that the fifth edition books are expecting in the game is ~40. \$\endgroup\$
    – Tyrrell
    Commented Mar 19, 2013 at 18:03

The average mage doesn't write books considered the learning book every covenant should have.

The books, that are copied and are considered standard were surely written by mages with virtues, which makes them great bookwriters / experts in one form / technique.
So we have virtues like Good Teacher (+3 to book quality), Affinity to Art, Study Bonus etc. to consider.

And there where surely mages with an obsessive search in one art, making them great there and useless in other things. So taking a mage with Affinity to Mentem, it would give in your example of 28 seasons learning 25 in Mentem. And 28 seasons are just 7 years, I don't find that excessive high.

So, for your summa level 15 and quality 13:
As you has shown in your calculation, we don't even need Good Teacher for quality 13.
For level 15, we need a Mentem score of 30, meaning 465 XP.
Simply using Affinity for Art, your assumed 8,25 xp per season, we would need 38 seasons, about ten years. Still, for a specialized magus, I don't think that is unreasonable high. He would not be a good adventurer, but why should he? Consider Stephen Hawking as a mage. Using Affinty to Art + Free Study (+3 when learning from vis) would reduce that to 28 seasons.

The average playable mage, who needs to be more than an one art idiot savant can't do this, but the order has enough members, so that some can write such good books and they would be copied many times.

  • 2
    \$\begingroup\$ +1 for getting to the root of it: The books that are considered worth getting aren't written by ordinary authors, because why would a covenant settle for an average author when there are much better ones available? \$\endgroup\$
    – GMJoe
    Commented Mar 20, 2013 at 6:28
  • \$\begingroup\$ This is the key point. Even if we're ignoring exceptional and rare books, we should expect most books in every covenant to be something that they wouldn't be able to make themselves; if you aren't in the top 1% in a particular field, then you'll be using something copied from their writings. \$\endgroup\$
    – Peteris
    Commented Oct 3, 2014 at 13:57


One possibility I have just thought of is that in previous editions, one of the standard twilight effects was called "Increased Understanding". Instead of a Magus being only able to write 1/2 their level, it would allow then to write 2/3 (or 3/4 etc. if gained multiple times) and it explicitly mentioned that some of the greatest books of the Order of Hermes were created by Magi who had gained such insights.

Although this twilight effect is no longer in the list of standard twilight effects, it has been a staple of the Ars Magica setting for so long that you can be sure that Tweet et.al. took it into account.

Combined with the 5th ed. ability to trade level for quality, your Magus with a score of 21 could potentially write a Summa of level 14 (21/2*3), very close to the 15 needed for a Level+Quality of 28.

Combined with a higher arts score (as Tyrell suggests) even one "Increased Understanding" could allow a Magus with an Arts score of 30 to write a level 5 book with a quality of 28, while a magus with a score 36 could write a level 9 summa with a quality of 28. In earlier editions I've seen characters with arts in the 40-50 region.

Politics and roleplaying

I suspect that this is more to do with the political clout that a covenant has than with the capabilities of the average members of the covenant.

A Spring covenant library probably gained most of its books from its new magi or their masters.It would be closer to a school library, full of watered down introductory texts which can only get you so far.

One of the defining features of Summer and Autumn covenants would be that they have gained in both magical and political power within the order. Part of this will have been Magi making an effort to go out and acquire exceptional quality books from covenants around the order, for instance doing a deal with Domus Magnus House Flambeau for the right to copy an exceptional Ignem text. It will have a library which contains many books which few of it's inhabitants could ever hope to write, much like a university library.

Thus for a Summer or Autumn covenant an exceptional text is standard.

By the time a covenant gets into Winter, the library (just like the power of the covenant) is on the wane. The best books have been traded away to other covenants or become damaged, while other books may be inaccessible because they are always hidden away in the lab of the mad arch-mage that no-one can talk to.

It would be quite logical for several houses of the order, especially Bonisagus, to train specialists who spend their entire career copying, writing and improving books. They would have been selected for their communications skills and trained from early in their apprenticeships to maximise their potential. Such characters would probably be quite boring to play in a campaign, but you can be assured that they exist somewhere in the setting. It would be the books of these luminaries which would be copied around the covenants of the order and revered as one of the marks of the transition to Summer.


A summa has a quality and a level. The books in the history of the order that have, because of their quality and fame, become the standards for their arts have a quality of around 28 -level. For example level 18 quality 10 or level 16 quality 12.

  • \$\begingroup\$ It doesn't answer my question. I know how they work, but I don't know how those numbers have been * achieved*. \$\endgroup\$ Commented Mar 14, 2013 at 0:53
  • \$\begingroup\$ Oh, I see sorry. \$\endgroup\$
    – Tyrrell
    Commented Mar 19, 2013 at 17:24

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