Hermetic Theurgy -- is it worth it?

Hermetic Theurgy is a Minor Virtue providing lots of (not always evident) benefits that come with lots of (not always evident) limitations. Is it worth taking? For which characters? Under which assumptions?

This is a spin-off from a thread about Flexible Formulaic Magic, where Ovarwa observed that Hermetic Theurgy, although superficially appearing to offer many of the same benefits, is in fact much, much worse -- so bad, in fact, that it's probably not worth taking even as a Minor Virtue. While I agree with some, perhaps even most, points made by Ovarwa, I disagree on the ultimate conclusions he reached. And since the discussion on Flexible Formulaic Magic yielded many useful insights, despite FFM being a more "straightforward" Virtue, I hope this thread will yield at least as much insight on the strengths and weaknesses of Hermetic Theurgy.

Obviously, few (no?) Virtues work equally well regardless of the character concept, regardless of his other Virtues and Flaws, and regardless of the assumptions on the "environment" of the saga (e.g. abundance of spell Lab texts) so I expect any significant discussion to take these into account as well.

Let me see if I can summarize the benefits and limitations I see in Hermetic Theurgy.

  1. Benefit: Since one works with spell spirits, a Minor Magical Focus in Magic spirits (and any Major Focus that includes it, e.g. a Major Focus in Spirits) is "amplified" to cover all your spontaneous and (non-ritual) formulaic magic. This is particularly useful for a generalist.

  2. Benefit: Invoke the Spirit of allows you to cast Formulaic spells varying their RDT as if you had Flexible Formulaic Magic (more or less, see limitations below).

  3. Benefit: Invoke the Spirit of allows you to cast "half-casting-score" Spontaneous magic (i.e. with totals on par with those of Fatiguing Spontaneous Magic) via a Formulaic spell, effectively reducing the risk of botching (e.g. by casting in a relaxed situation, or investing 5xp in mastery), possibly eliminating fatigue etc.

  4. Benefit: Because Invoke the Spirit of is a Formulaic spell, it Hermetic Theurgy provides access to Spontaneous Magic even to those Magi who can't do it, or can't do it very well -- e.g. those with Mercurian Magic, which incidentally synergizes very well with daimonic summonings (see below).

  5. Benefit: You can research your own daimonic summonings (no need for a Lab text), and are a little better than other magi at casting them (basically, you can summon really mighty Daimons if you are willing to sacrifice really gargantuan amounts of vis). Daimons are nice in that they can pull off all sort of non-Hermetic tricks; plus, when dispelled, they tend to leave around vis that is not necessarily of the same type used to summon them.

  6. Benefit: The penetration of your spell spirits is determined, as for magic items as 2 x the number of "extra" levels you place in the spell. This means that even if you have Weak Magic and no Penetration skill at all, your Level 50 "Pilum-of-Fire" spell spirit can still achieve a rather impressive 2x(50-20)=60 penetration.

  7. Benefit: You can summon a veritable army of spell spirits, recover all your fatigue (if any was lost), and then walk around "ready to fire them", with no penalties from fatigue, wounds, lack of gestures (presumably), and/or an almost inaudible voice (again presumably) -- and ZERO chance of botching.

  8. Possible Benefit: it's not clear how smart your spell spirits are. But since they apparently need a modicum of intelligence to understand your instructions ("target the red-haired human with a sword!") you could conceivably tell a D:Ring spell spirit to e.g. attack the first person entering the room. By the same token you could also instruct multiple spirits to act together or in sequence. This is tricksy stuff.

  9. Limitation: unless you are willing to pull it off by casting Rituals, the pseudo-spontaneous magic cast with Invoke the Spirit of will not exceed 5th magnitude, and possibly 4th magnitude if cast with sufficiently long "hanging" durations.

  10. Limitation: you need a different Invoke the Spirit of spell for each Tech+Form+Requisites "area" in which you want to gain access to "pseudo-spontaneous" magic. This can grow to a lot of spells in some areas of magic.

  11. Limitation: Theurgic spells are probably less common than "standard" Hermetic spells, and have this unpleasant limitation that they can't be "held" simultaneously by multiple magi; so Hermetic Theurgy interacts poorly with Lab Texts.

  12. Limitation: It's one round to summon your spirit, and one round to instruct it, so if your spirit is not hanging around, in an emergency you are slower to react.

  13. Limitation: Your spell spirit gets no benefit whatsoever from arcane connections, (your) high Arts, vis, a booming voice, your talisman attunements etc.

  14. Limitation: Most mastery options are rather ineffective when summoning spell spirits, and your spell spirits can't benefit from mastery options.

  15. Limitation: Your spirit is not you, so it cannot affect you at Self Range nor your spells at Touch Range, cannot open an Intangible Tunnel for you (or for other spell spirits), cannot bypass your familiar's Magic Resistance, has no Arcane Connection to your Talisman etc.

Another potential weakness could be that if your spell spirits are hanging around waiting to be used, another magus could target them with his own magic to either neutralise them or turn them on you. The high might of anything truly dangerous makes this unlikely, but against another spirit master it could get messy.

If you have flaws with regards to Spontaneous casting, spell spirits are suddently much more useful.
Maybe I should actually get around to writing that up for Sub rosa some day.

That's point 4 above, right?

Dunno, didn't read the list :wink:
I had to leave for practice.

Hermetic Theurgy is fantastic for Muto Vim, which is essentially "the TeFo you'll probably be casting spontaneously a lot". However, you'll need a reasonable chance of casting a lvl 50 effect to get it to work decently, so that kind of limits your character concept to "MuVi expert". However, seen in that context, it's essentially a minor virtue that keeps you from spending fatigue, botching your character's core TeFo, or having to make a Concentration roll, which is pretty good.

Uhm... would you care to elaborate? Why is Muto Vim "essentially the TeFo you'll probably be casting spontaneously a lot"? If I understand, you are saying that Hermetic Theurgy is great to cast "pseudo-spontaneous" Muto Vim magic: you cast an Invoke the Spirit of "Muto Vim", let's say at level 50 (the max), and use the metamagic it provides to affect spells up to 5th magnitude in various ways?

I'd say casting reliably level 50 spells is not that hard for a character with e.g. a "magic spirits" minor magical focus (which covers essentially all his theurgic spellcasting): a little hard to do reliably at character creation (though not impossible, with Puissant/Affinity for both Muto and Vim), but relatively easy with a few seasons of study (start with both Muto and Vim at 10, and bring them both to 15, for a total of 130xp).

It makes sense, though I'm not sure it's worth it:

A MuVi specialist likes to cast many different kinds of niche MuVi spells, each getting the exact change desired tailored to the exact situation encountered. Learning these as Formulaic spells is almost pointless. Too many spells for all those specific situations.

A level 50 Theurgic spell to allow any MuVi (no reqs) at level 25 solves the problem, if you don't care about doing better with MuVi. In games where level 50 spells are automatically rituals, this won't work as well: You'll be limited to level 20 MuVi.

There is a caveat: Casting MuVi alongside some other spell gives you a more advantageous Concentration roll than usual. You lose this benefit with the Theurgic version. First round, you cast the theurgy spell. Second round, you cast some other spell and at the same time tell the spell spirit what to do, which involves normal penalties for trying to do two things at once.

What Ovawara said, with the explicit comment that you actually need a higher lab total than 50 if you want to develop the spell yourself. Arguably you could get a pre-made spell from your Mystery Cult (assuming someone else already developed it), but that's beyond the scope of the discussion - I usually assume that people with Hermetic Therugy develop the spell on their own, in order to avoid the whole "two separate people summoning the same spirit" issue.

Although having a MC that's been around long enough for there to be a library of available-for-the-new-initiate spirits is an interesting idea.

But yeah - MuVi is the one TeFo in Ars that you probably don't really want to take many formulaic spells for, unless you have a lot of one particular Form that you do a lot with. "Alter the Realm of Magic" would be a decent one to know, if you had a lot of non-combat Vim spells that you wanted to shift from Magic to, say, Farie. Another one I like is "Transformation of the mystic Rampart" - which changes a Circle/Ring ward to Touch/Day. (I usually argue that one doesn't need to be form-specific, as thematically it's linked by concept: mutating a ward to a different kind of ward. However, that's probably not RAW.)

that being said, having a 50 MuVi casting total means that you can /5 spont a lvl 10 effect, which means that (assuming you use ReVi casting tools), you can actually get a good amount of mileage out of just that. Using Hermetic Theurgy then becomes "the next level" of spont casting.

Is this canon? I usually interpreted it as "Round 1: summon spirit (which includes the instructions for telling it what to do) - cast the spell the 2nd round, and the spirit then affects it and goes away". I've usually ruled that "Instant/momentary" can start at the end of its current round, and last until the end of the next round. (Or technically it starts at the end of the Magi's Initiative order, and lasts until the end of the same initiative order the next round.)

EDIT - regardless, the character concept has Cautious Concentration (and a moderately-high level in that ability) already, simply to get the /5 spont magic working (mostly) without fail. I do agree though that if you need to cast this with the regular Concentration penalty, it becomes less attractive.



No books handy.

But casting the spell takes one round, and this summons the spirit. Instructing the spirit takes a second round, and the spirit uses its power on that second round.

If casting the spell and instructing the spirit occurred at the same time, then longer duration versions would truly suck, because you'd instruct the spirit far in advance what to do. The spirit stays around for duration Sun and you instructed it how to FFM in the morning? And when during the day to cast the spell? That's really unuseful.



Ovarwa is correct, as best I can tell.

Here's my take on the number of lab texts available to a theurgist.

Hermetic theurgy is a mystery virtue and to get it more often than not the character will need to be associated with a mystery cult. Specifically a mystery cult that does Hewrmetic Theurgy.

This mystery cult will almost certainly collect therugic lab texts for it's members to use. what would be a reasonable number of texts for a cult to have access to?

Here are a set of assumptions, you should probably run through the questions yourself and see what result you get.

how long has this cult been around?
what has been the average number of magi in the cult?
how often have these magi created spells?
What proportion of the spells that the magi created are theurgy spells?
What proportion of the created theurgy spells have made it to the mystery cult?
What proportion of the spells are duplicates?

Here's one set of answers
the cult is 150 years old
it has had on average 12 magi in it throughout its history
the magi create about .75 spells per year per magus
about half of their spells use hermetic theurgy
around 75% of the theurgy lab notes have made it in to the hands of the cult
because the cult communicates well only about 10% of the theurgy lab texts are duplicates of earlier work

This gives us 455 lab texts, obviously with different assumptions you'll get different numbers. Yet I think this is a strong argument that you can have a consistent setting with lots of lab texts available to the players.


A nice way to estimate, though I think the choice of questions to include and exclude and the underlying assumptions are highly optimistic.

  • The idea that there exists a central Mystery Cult repository or center independent of its members seems unlikely. If A creates a spell and publishes it, that can easily just involve sending a letter to B and maybe C. Are D-G really worthy of this new knowledge? And it's been a long time since anyone has chatted with H-J, who are off on the other side of Europe. The less we say of K, the better... But it's pretty likely that the 12 Theurgists don't all know each other, either because they aren't in the same cult or because cultists tend to be secretive.

  • Disseminating spells to other magi in the cult makes the spell less effective for you: RAW, if someone else has the spirit on tap, you cannot. If the other cultist is careless or malicious, the spell becomes total dead weight. Unlike regular magi, theurges have a great incentive not to share, even beyond the "You're not cleared for this."

  • There's no accounting for texts that get lost or spell spirits that have been killed.

  • 0.75 spells per year per magus seems optimistic. Magi tend to spend lots of time boosting Arts. Cultists tend to have other time sinks too.

Even a casual eyeballing of your results seems unnaturally optimistic: I don't think the core rulebook lists 455 distinct spells for the entire Order.

I wouldn't be surprised most lab texts are found rather than traded, and that a surprisingly high percentage let you summon a spell spirit that no longer exists.



indeed it is more likely that such lab texts would form a personal library that would be passed on after the death of the inventing magus. In which case the primary questions will be rate of spell invention, how old a given lineage is, and whether such spells are likely to accumulate or divide at inheritance (in other words are you more likely to pick up the complete works of two masters, or half the works of one upon their death)

They're somewhat optimistic but they're not unreasonable

I think that the purpose of a mystery cult is more often than not to facilitate the magical growth of it's members. I had posited 12 theurgists in the same cult, not 12 in the entire order. 12 strikes me as about average size or smaller for a mystery cult. If getting the mystery cult members more power is the purpose of the cult it becomes less difficult to explain why they get lab texts out to each other than why they don't. Mystery cults actually do demand their members do service in order to qualify for the next initiation, it's right there in the text.

If a mystery cult wants to have lab texts (and I can't see why they wouldn't) they would want their members to leave instructions to send their theurgy lab texts to other cult members upon their passing. It's not unreasonable for them to see this as quite important. Certainly people's estates aren't always split up as they would have liked, but theurgical lab texts have very little value to those who aren't theurgists thus claims by cult members are less likely to be disputed.

If there are 11 other theurgists in my cult, and they have access to my lab text, perhaps 1 or 2 might eventually learn it. How big of a deal is it to possibly get a busy signal for the spell? I'll point out that the duration for invoke the spirit of [spell] is momentary, the spirit will spend "a round or two" to cast the spell and then go away until summoned again.

If you look again you'll see I eyeballed that at 25% of all the spells. Granted magi cause drama and drama causes tragedy, but on the other hand spirits are more or less immortal and won't get into trouble on their own. Also it is my opinion that the time you are least likely to want a theurgic spell is in combat where the one or two round delay will literally kill you ergo spell spirits are exposed to violence only very infrequently.

Three spells in four years seems about right in my experience but if you lower it to 2 spells in four years you can still end up with a large number of lab texts (let's not forget that one of the additional time sinks for cultists is service to the cult).

Optimistic but not unnaturally so. There are several factors that make collection of lab texts by cults really likely.

I've always thought of the core book spells as just a list of examples that make up only a small proportion of the hermetic spells.

I think that the underlying assumptions that lead to my optimistic scenario are very reasonable. The assumption can be summed up as - the lab texts are important to the cult so the cult makes a reasonable effort to both acquire them and keep them available to the cult-. This is I think at least as reasonable as the assumption that the cult -as an organization- won't act to ensure availability of lab texts.

I agree with this but I'd posit that copying lab texts from cultist to cultist is likely to be some of the service that cult members do for their organization in order to qualify for the further initiation.

I think it will vary depending on the cult. The Titanoï and the Cult of Heroes both use hermetic theurgy, and it is likely that the latter cooperate a lot more than the former.

And given the number of magi in each parent house, the number of initiates in each of these cults is likely to be rather less than 12.

Here's another way to look at it. Ok, if you think there are many more spell lab texts available in the Order, how many do you think there are?

Then, the number of these that are HT spell lab texts should be:


Working backward, I get something like TotalSpells = 455/((12/1100)*(120/500)), which is more than 170,000 lab texts floating around the Order. More than 150 unique texts per magus! Does this match your number? Does it feel right for any saga you've seen?

And that assumes that every spell a cultist creates uses HT, that cultists are no more or less secretive than anyone else, that cultists don't have extra demands on their time compared to ordinary magi and can invent the same number of unique spells, that spell spirits don't get killed, that the likelihood of any spell text being completely lost or destroyed is equal...

Now, we can argue that the Order hasn't always been that large. But then we would also have to argue that various cults have also started off much smaller. Worse, each new cult has to struggle to get off the ground, but the Order as a whole only had to start up once.

Using my questions to estimate the number of lab texts in the order

the cult is 350 years old
it has had on average 1000 magi in it throughout its history
the magi create about .75 spells per year per magus
about 90% of their spells use standard magic theory (rather than holy magic, theurgy, numerology or some other thing)
around 30% of the lab notes are still in the hands of the order, the order doesn't value them as highly and it is older also some of the earlier work is obsolete.
because the order is larger and do to logistics can't have the communication or sense of purpose of the cult 60% of the hermetic lab texts are duplicates of earlier work

This gives me 28350 lab texts in the order that's 22ish per magus. That seems about right to me