Let's Design a Hedge Tradition - Step 2: Set Parameters

In a continuation of https://forum.atlas-games.com/t/lets-design-a-hedge-tradition-step-1-brainstorming/8119/1 I think the brainstorming thread has just about covered all of the published details on the Cult of Mercury so now I think we're ready to set our design parameters!

For the sake of convenience, I've divided the results of our brainstorming session into Crunch and Fluff.


  • They were individually weak and apparently incapable of spontaneous magic at all.
  • They were capable of conducting great rituals requiring many participants and prodigous quantities of Vis.
  • They apparently had very weak Enchantment abilities outside the Cult of Vulcan.
  • They invented 'Wizard's Communion' and a number of other Hermetic spells such as 'Hermes' Portal'.
  • They may have improved their magic primarily through a process similar to Spell Mastery.
  • They possessed 38 Great Rituals though what these were and how they differed from their regular rituals is not known.
  • They conducted magics in the Hercynian forest that are still functional as of 1220.
  • They are believed to have possessed great divinatory abilities.
  • They seem to be very free with defining their targets.
  • Individual spells are possible but suck, mastery is very important for them, big rituals are easy for groups.
  • Able to cast ritual magic with HUNDREDS of participants.
  • No spontaneous magic that we know about, but able to cast (at least) low level spells by themselves.
  • Able to cast spells that affect large areas, maybe as large as the whole empire.
  • Spectacular magics required the use of large amounts of vis. Lesser magics may have required vis too.
  • They worked around some formalized large rituals.
  • The high priest surely were Gifted, but the lower ranked members not necessarily.
  • They are said to have extremely limited magical repertoires, rarely exceeding a dozen or so spells.


  • They absorbed the Cults of other classical deities, bringing their magic under its own Aegis.
  • They were at least nominally led by the Roman Emperor.
  • Their magic system had been fragmented by Bonisagus' time and thus it was not integrated into Hermetic theory.
  • Elements of their magic live on, however, among the Order's various Cults and Lineages.

Naturally, there are large number of ways for these requirements to be met. Therefore, I'd like to devote this thread to discussing various mechanical systems to meet the parameters as well as a few sample spells to use as an acid test. Ideally, all recommended systems will be subject to constructive criticism to aid in their refinement into something that will, hopefully, resemble the magic wielded by the CoM as described in so much Ars Magica fluff.

Well I guess that's it for now, I'll be posting a few of my own ideas just as soon as I find the time to write them out!

Could you clarify what you mean by "design parameters"? We throw formulas for magic, we decide on the type of magic areas that the cult covers? We decide how many cult members were out there and where?...


I meant the goals we're trying to meet in terms of design (which I've already listed above). So basically, this thread is for people post and then critique different ideas for mechanical systems that can do what you think Mercurian magic ought to be able to, discuss its pros and cons, how it might be improved and so on and so forth.

With any kind of luck, I'll be able to demonstrate later today! :slight_smile:

Before we go into mechanics, shouldn't we discuss the effects that Mercurian Magic should achieve? I have my own set oif mechanics more or less defined, but I think something about what we are aiming for in terms of effects should be important. :slight_smile:

As a side note, I think that the magic item reference to the Cult of Vulcan is not necessary: Vulcan is a totally different cult, so they do not need to share mechanics in the slightest.

So, going for the first point, what do we know about the effects of Mercurian Magic?

  • Rip a large magical entity to shreds (Hercinian forest)
  • Create and manipulate Volcanoes (Guernicus tradition)
  • Do something with the roads, IIRC, probably speed up passage through them
  • Mercere portals are a direct reference to the Mercurian cult magic, IIRC.
  • Manipulate the climate?
  • Do we consider Fenicil's rituals as per HoH:TL to be kosher Mercurian magic reference?

IMHO, no.

I could be way off base, but my opinion is that it will be easier to define the Cult's individual powers thematically once we have a firm idea in mind for exactly how those powers are going to work mechanically than vice-versa.

That said, feel free to sprinkle comments on the appropriateness of any example spells posted since it certainly constitutes an important area of our discussion on the CoM and its magic!

OK, here comes my very personal version :slight_smile:

I think that a system akin to that of the Augustan Brotherhood + huge consumption of vis (1 pawn per spell level) + Ceremony can work well. Couple that with an Hyperborean-small magics method.Breaking it down:

MAGIC ABILITIES: Like the Augustan brotherhood. Difficult Arts + each spell being an accelerated ability of its own.

RITUALS: Need to have the Associated Difficult Art be equal or higher than the actual Magnitude of the Spell (Spell lvl/10) in order to cast it. So casting level 40 rituals is feasible, but requires someone with the Difficult Art at 8. Far from normal ratings.

CASTING: Pre (or other characteristic) of leader + Artes Liberales + Difficult art of each participant (including leader) + D10. You can get a bonus to your casting total using F&E bonuses up to double your Difficult Art level. Casting costs 1 pawn of vis per LEVEL of the spell.
You need dozens of participants to have a chance to cast the big stuff, and even more of them if you have to achieve any meaningful penetration.
(I am unsure about adding AL to the mix)

SMALL FORMULAICS: For each point you get in a Difficult Art, you get 5 points to invest in formulaic spells. Those include uses per day and (if you want) extra penetration. (So these are designed as magic items, in practical terms). You can save them to get a higher spell effect later on, when you accumulate more points. You can also spend those points improving your current spells. The base effect of the spell cannot be higher than 4. SO, if you have a score of 5 in a difficult art, you get 25 spell-like levels.

CASTING FORMULAICS: Difficult Art + Philosohiae + F&E + D10. F&E up to your Philosophiae Score
PENETRATION: (Casting total - spell level) + Pen*Pen.Multiplier

This is how I would do it, but am extremely open to suggestions. :slight_smile:

OK, as promised here are a few of my ideas for systems that I think could successfully represent the Cult of Mercury's magic. Obviously, some have been given a tad more thought than others, but I'm not completely satisfied with any of them and would love to hear other people's suggestions for improving them.

Option #1.

As briefly mentioned in Step 1, this method was developed by taking a synchretic approach to combining Fenicil's Rituals (HoH: TL) with Vigilo Magic (RM).

Under this method, each cult possesses a certain number of Schools (not unlike those used by the Augustan Wizards) representing particular aspects of their patron deity (for Mercury, Herald, Shepherd, Thief, etc). These schools would be used to design spells using a set of guidelines created using the same method CJR used for Vigilo Magic (Hermetic level x 3 or Magnitude+4 x 3, whichever's lower) though naturally these might be adjusted up or down a few magnitudes for specialized traditions. The schools themselves don't contribute to Casting Totals, but do confer Magic Defences and limit how much Vis can be used per season per ritual participant.

Whenever a Mercurian learns a new spell, he gains a Spell Mastery ability of 1 in that spell which is then used in the casting total for the spell. Most other aspects of Mercurian spellcasting are as per the Augustan model except that Mercurians have the option to cast cooperatively as per Fencil's Rituals and have various secret methods (Mysteries) for reducing Vis costs.

One other ability requires special mention: Communion. Communion is the Mercurian equivalent of Ceremony and works in much the same way except that it automatically increases to remain equal to the caster's highest Spell Mastery ability.

[i]Example 1: Justin seeks to cast a Mercurian equivalent of 'Chirurgeon's Healing Touch' (Base 15, +5 = Level 20). The spell has an EF of 21, +3 Touch for a total of 24 and thus costs 4 pawns of Vis and takes an hour to perform. Note that the Vis cost and casting time are identical to that of a Hermetic magus.

Stamina 1 + Spell Mastery 4 + Aura 3 + Stress Die 6 + Communion 4 - Participants 1 = 17; almost enough, but not quite. With a few more spell mastery points from his fellows, however, he might make it...[/i]

[i]Example 2: Justin, along with a small group of his disciples, are asked to summon up a former Emperor's ghost to advise his successor (Base 15, +4 AC, +2 Ring = 45) for a an EF of 39. The ritual requires 7 pawns and takes 1 hour, 45 minutes to perform. A Hermetic would require 9 pawns and 2 hours, 15 minutes.

Stamina 4 + Spell Mastery 11 + Aura 3 + Stress Die 6 + Communion 18 - Participants 6 = 36; this ritual goes off without a hitch. The Emperor rewards Justin handsomely.[/i]

Pros: Low-level spells proportionally more difficult than high level ones, Spell Mastery is extremely important, guidelines are fairly easy to calculate, number of spells known is kept low by need for Mastery.
Cons: Group rituals may be too powerful, low level rituals are costly in Vis, School guidelines must be compiled, Learning new spells isn't hard, Hermetics with Mercurian Magic are superior in every way.

Option #2.

This method uses a less in-depth model, but one that I think might work better under some circumstances under it, the Mercurians can't invent spells at all per se doing away with the need for Schools or Arts. Instead, any spells or enchantments exist as Lab Texts passed down from Antiquity.

Spells are learned automatically with a value of one can be improved with experience according to the abilities scale as per Spell Mastery. Ease Factors for the spells are equal to (Hermetic value x 3). Spells can only be cast, however, if the group's combined Wizard's Communion spell total is equal to or greater than the spell being attempted in which case the Level is divided by the number of participants to achieve a Casting Total.

Naturally, casting time and Vis costs would be identical to Hermetic equivalents though they would benefit from the effects of the Mercurian Magic virtue.

[i]Example 1. Chirurgeon's Healing Touch is a Level 20 spell for Hermetic Magi so it's Level 60 for Justin and his comrades. There are 4 casters and each knows Wizard's Communion at Level 20 for a total of 80. This reduces the EF of the spell to 15.

Stamina 0 + Spell 5 + Aura 3 + Die 6 = 14; this ritual goes off healing the target. Note, however, that Justin would have failed completely on his own.[/i]

[i]Example 2. The Ghost summoning above (Hermetic Level = 45) has a truly impressive Mercurian Level of 135 so Justin calls together 8 of his most trusted allies to participate. Their combined Communion of 150 is sufficient to reduce the EF of casting to just 15 (again).

Stamina 0 + Spell 4 + Aura 4 + Die 6 = 14; the ritual is successfully cast yet again![/i]

Pros: Easy to work with, strongly emphasizes low-level spells for individual, high-level rituals easily cast as part of a group, implements Wizard's Communion.
Cons: Single casters are all but helpless, even small inexperienced groups can be very powerful, no power progression in spells learned, lots of spells can be learned.

Option #3.

Under this method, Mercurian Wizards possess a series of virtues that work like Folk Magic in TSE.

Basically allowing the wizard in question to use Magic Lore to perform certain free-form effects associated with particular Hermetic guidelines. Thus, Mercurius Fur might be associated with Perdo Imaginem or Muto Imaginem effects while other virtues grant other guidelines.

Such spells, in accordance with the rules for Folk Magic would require a minimum casting time of 15 minutes, but not necessarily any vis. Casting Totals are necessarily low, but not quite to the point of uselessness and can be enhanced for group casting by any of three methods.
A. Ceremony - adding Stamina, Magic Lore, and Group Bonuses of extra participants
B. Communion - Dividing spell levels by # participants.
C. Vis - Casting Totals are boosted with Vis, but each participant can only spend a single pawn so large groups are required for large-scale castings of any sort.

Personally, I'm especially fond of C, but it might work best paired with A or B. In any case, if this option were chosen, it would require a rather poetic interpretation about the nature of spells in which we attribute concerns about the Cult's repertoire to the fact that any given Mercurian is unlikely to be able to cast more than a handful of very simple spells on their own.

Pros: Low Casting Totals, scales well, vis intense, tradition is useful and fun at all levels.
Cons: No Mastery, awfully close to spontaneous magic, dividing die rolls is annoying, possibly too costly.

Alright, so that's a lot to take in, but I look forward to your critiques as well as hearing about your own suggestions for mechanical systems that could represent Mercurian spells in Ars Magica.

Copy-paste of my post in the other thread, with a few mods to require more people.
I also think they should be able to cast some individual spells. The founders, and sorcerers of their time, demonstrated this.

Take the hermetic guidelines,
If the spell is to be a formulaic, double the level to determine spellcasting EF, else don’t change it.
Keep the "lvl 50 = ritual" guideline, so that all old "lvl 25" spells are now rituals.
Every spell can be cast as a ritual (which is useful to make them castable at all), should the mercurian choose so.

Take every technique/form combination, and make it a single ability. For exemple, some mercurians would have a "CrIg" ability, others would have a "InCo" one.
Casting total becomes Stamina + Appropriate ability + Spell Mastery (ceremonial casting being a common mastery) + die.

Rituals cost 4 times their magnitude in vis (so a hermetic lvl 25 ritual needs 20 pawns). The Mercurian Magic virtue still works, hopefully.
When people cooperate on a ritual casting, the primary caster makes the roll. He adds to his CT the Spell Mastery ability of every participant that has the required ability (CrIg, InAu, whatever) at 1+. Those who don't give a bonus based on the Arts table, using their number as XP, so that 55 helpers give +10.
You can spend vis to get + 02 to casting total

So. A bunch of mercurians want to cast “The Bountiful Feast” (CrHe 35). This costs 28 pawns of vis.
The leader has Sta 02, CrHe 6, and Spell Mastery 4
Say, the leader manages to get 50 guys for this.
05 are gifted priest or initiated mundanes with CrHe1+ and an average Spell Mastery of 3: They contribute 15 points. The rest only give him 08 pts
He roll his Sta 02 + CrHe 06 + Mastery versus 04 + 15 + 08 = 35 + die vs Ritual EF 35.

The same guy want to cast a lvl 75 hermetic ritual (vis cost 60).
He manages to get a lot of help: 10 guys who can contribute a Spell Mastery 3, and 300 mundanes.
The spell mastery guys give him 30 pts, the mundanes 24.
He rolls his Sta 02 + CrHe 06 + Mastery versus 04 + 30 + 24 = 66 + die vs lvl 75. Time to spend some more vis!

Now, you’ve got a proto-flambeau that know CrIg 6, has stamina 2, is in a friendly lvl 05 aura, and has mastered a primitive PoF (does +05 damage at voice range, hermetic lvl 10, mercurian formulaic EF 20) to lvl 05. His casting total is 6+2+5+5= 18 + die vs lvl 20. Not very impressive, especially given all the dedication he put into it.

This is rough and may need to be polished, but:

  • It seems to mostly work: individual spells are possible but suck, mastery is very important for them, big rituals are easy for groups and Mastery is still required.
  • You can easily transition from there to hermetic magic: Bonisagus separated the techniques and forms, making spellcasting easier. This may have cut formulaics levels in 2, or this may be the result of further work, just like the transition from difficult arts to “normal” ones.
  • The need to spend XP on each TeFo combination + each mastery implies that their spell repertoire will be quite limited