Hard-to-Find Rules

Which rules do you think are hard to find in the ArM5 core rulebook? I am mainly interested in rules that are in the book, but that are not where you expect them to be, or not where they are often needed. Obviously, if there is a rule that is missing completely, please let me know, but we should have spotted that by now. (See the other thread for rules from other books that you think should be in the core.)

Please post here, so that other people can post agreement, and possibly be reminded of things that they find difficult.

I am afraid that I cannot, right now, say much about why I am asking about this, except that it is not purely personal interest.

Please do not post anything other than hard-to-find rules in this thread; I have created another thread for speculation about why I am asking this. If this thread gets cluttered with other posts, I might miss things, so I will move posts that do not belong here.


Here's a few issues that appeared after the ArM5 core book came out, and took some time to sort out:

  • Is a ritual spell a formulaic spell?
  • The process of casting spells might be described more precisely wrt Ranges and Targets: e. g., how long do I need to touch to cast a R: Touch spell?
  • Penetration of wards and the Aegis
  • Details of the Aegis
  • Working, especially timing, of Muto Vim spells
  • Wizard's Communion on rituals
  • Interworking of Iconic Species, light and shadows
  • Magically duplicating memories bestowing Abilities
  • Directly creating Intelligence with Hermetic spells and effects
  • Guidelines for moving stuff by Rego
  • Rego Craft magic (IMO this is core enough to be in this list)

It would be nice to have these topics addressed in a supplement or revised core book. It might help to go through Guideline lists for those which should have been in the core from the beginning.


The following two topics are scattered around several supplements, and not even the most obvious ones. They come up a little too often to be so haphazardly treated. Collecting and completing the rules would make it a lot easier.

  • ships and navigation (HP, LoM, C&G)
  • familiar/animal design (HoH:MC, RoP:M, a few web supplements)
  • Penetration of special abilities for beings with might ( I can nevr find this quickly)
  • a list of what the modifiers to spell levels do (is touch +1, what level is smell?) The descriptions are there, but a table with numbers on would be nice

Wizard's Boost is so vague (and outdated) that it sparked that whole nasty thread a while back.

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Very true. We made that table ourselves and each player has a copy, so it's so ubiquitous in our game I even forgot we had to make it!

What is going on with the MuMe comment about applying Intellego senses to a group? It's the first full paragraph on p.114. It's never explained how this is done at all, so it's impossible to find. The statement only adds a level of confusion beyond saying nothing at all, and something like extra magnitudes also need to be included for Group would take as much space and be helpful.

Specify that "level" in a guideline is the guideline level rather than the spell level. That has confused a lot of people.


My players have always whined about there being no easy chart with range, duration, targets, and sense magnitude in the base book.

  1. Reputation comes to mind
  2. Confidence points
  3. The ability chapter does not spell out all the rules governed by the abilities. i.e. Magic Theory of 3 is required to build a lab is in the lab section. Needing a language score of 4 to read a book, and a score of 5 to write a book is not there either.
  • Form Bonuses on page 77 are in a weird spot.

I think there should be three categories of magical limits, Greater Hermetic limits, lesser hermetic limits, and limits of the magic realm such as the limit of the Infernal which is true of all powers related to magic which often gets lost being as it is in the infernal section of the realms chapter. I don’t think any of the other hermetic limits fall into this category but I may be wrong.


Bringing something from a post accidentally placed in the errata thread to here:

A lot of people get confused by "study one of these Arts (that is, gain at least one experience point from study)" under Elemental Magic. If you dig deep enough, the answer is there: generating an Advancement Total from which you gain experience. But that takes a lot of digging to find that Advancement totals only arise from "a season in study" and confirmation that exposure is "by being exposed to the thing to be studied" and that an example of study is given as "perhaps from Adventure experience." Simply changing the parenthetical note to be about Advancement Total rather than what it currently is would clarify it immensely for people.


I think a nice 2-3 page detailed table of contents in the core rulebook would solve most of my issues.

Combat being on page 171 in a chapter called obstacles was strange enough to me that I added it to my table of contents. I get the why of it, but I would just call it Combat and it's own chapter.

Vis sources at the end of Realms of page 190 is strange to me. I would suggest all vis rules in one place, or if needed to be separate, put it in the covenant chapter.


The actual length of a Pace comes immediately to mind.


A pace is actually a standardized unit of measurement. There are four variants consisting of: United States, Ancient Roman, Byzantine, and Welsh. We can ignore the United States (didn't exist yet), Byzantine (not standardized between Greek States), and Welsh (limited to an extremely small area) versions.

The Ancient Roman Pace is the most likely distance referred to in AM. It was standardized in 29 BC and consisted of two complete steps, roughly 5 Roman feet. That works out to about 1.48 meters or 4 feet 10 inches. The Roman Mile was 1,000 Roman Paces, roughly 1,617 yards (1,479 m) in length.


That's all great - but its not in the book.

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You just proved Heru Kane's point. We know a pace is very nearly equal to a modern imperial yard, three feet. That you did not arrive at this despite it being written in a bunch of places in the book illustrates that the rule is a fairly hard-to-find rule.

I would include that a round is 6 seconds as well as a pace being 3 feet. For the pace, though, it could be worth a comment that setting it to 1 meter is close enough and might work better for many troupes.


Google tells me 2.5 ft, which comes up to a very handy 15.625 cubic feet for every cubic pace for calculating a base unit of terram.

You're just proving the point further. Google is very unlikely to give you an Ars Magica answer. Have you tried using Google to find the rules for a Talisman? ArM5 itself specifies that its pace is basically a yard. So we have a bunch of people demonstrating that this really is a hard-to-find rule. Heru Kane was definitely right to point it out as one.

p.112: ten paces per round (five feet per second)
p.172: A single combat round, consisting of one attack from every party to the combat, takes about six seconds.

p.113: one hundred paces (three hundred feet)

p.121: five paces (fifteen feet)


I think any ambiguity about "pace" is more that the players are being too 'smart' for their own good.

As far as I can see, there has never been any intent for "pace" in Ars Magica to be read as anything other than the common US definition. Ars Magica is written in standard US English. "Pace" just seems to have been picked because it sounds a bit more "ye olde" than "meter".

Likewise it is assumed that "minute" will be read in modern US English.

The difficulty arises when players realise that there are various archaic definitions of pace, and erroneously suppose that "pace" is meant to be read as part of an in-character measurement.