Which of these seems like the more productive way to get a new virtue? Could a mystery cult initiate something like fertility magic even though there are no living practitioners?
The way I read the rules, a mystery cult can in theory initiate any virtue. Whether anyone knows it already is completely irrelevant, The question IMO boils down to how you want to tell the story about the cult in you saga. If a mystery cult can initiate anything in practice, it becomes a free lunch, so I think the Cult needs a deity or another mystic force with a purpose, and only virtues serving the purpose may be initiated. A character who wants to invent a lost or unknown virtue can have quite a challenge finding a mystery to form a new cult around. If you want a free lunch, you can tell that story, if you want to make it a challenge, that's a valid story too.
I don't think the two approaches are comparable. Hermetic research takes a long time, because there is usually several failures for each success, and you need quite a few successes. It does not strictly require a lot of skill, although MT helps reduce the risk. Other skills and arts may be mediocre. Any Hermetic magus can do it. Self initiation OTOH requires exceptional lore and presence, but it will usually only take a few seasons per project. However, it is only an option to those who have found an appropriate cult, something which you can make as hard as the story deserves.
Do they have an Initiation Script for whatever virtue you want?
If yes, then absolutely!
If no... more tricky.
It seems to me the difference is in up front cost versus per virtue cost- the cultist needs a cult lore+presence where the researcher needs magic theory+int, but the magic theory route is more broadly applicable, and should be easier to find, so even getting to this "starting line" the cultist is at a disadvantage.
Initiation without the virtue is difficult, and if nobody else has the virtue that means a script needs to be developed- even if you have a maxed out presence of 5 and cult lore of 9 you aren't going to be able to self initiate anything without developing a script first.
If you are initiating a minor virtue (fertility magic) then you need script+pres+lore of 18, so a minimum of a +4 script, which requires a roll of 13 with int+cult lore- if the magus has even a 2 intelligence and a 9 cult lore they have a 90% chance of success on a roll without risk modifier, but the experimental results are a bit more risky since they affect you (or your experimental victim) instead of simply a spell design. Also with lower scores it becomes significantly harder as the work must all be done at once and cannot b broken up into smaller experiments as with research- a major virtue would require a script with a bonus of 12 and a target number of 21 to invent, meaning initiations for major virtues are virtually impossible to achieve since the die is simple for determining whether the new script is successful.
The other issue is what happens when a virtue cannot be achieved- the SG has decided it cannot exist for whatever reason- with experimentation you can probably determine this fairly early on in the process and potentially discover some related breakthrough, while with initiations this is not so clear, and I don't see a mechanism where a cultist discovers that they are pursuing the impossible.
Int is not that important. Magic Theory of 11 is good, because it allows a risk modifier of 3. You can happily invent low level spells with a low lab total though. High level spells is a double edged sword because of the warping.
Well, there is an advantage to using ancient magic integration, which saves on warping from the typical original research approach - it's safer to try and recreate something that exists outside of the order, or existed but disappeared and is being recreated, than to create something no one has done before (with the downside that you need to locate insight sources instead of just going on a hunch experimenting). Could someone self-initiate into a fertility magic virtue? I think that's beside the point. It can happen if the magic is alive and known within the order, with the right mystagogue. For something that is outside the order of hermes' capabilities, then no, initiation probably cannot occur without integration using the rules found in ancient magic. So for fertility magic to be able to be initiated, you have to decide as a storyteller someone else already did the integration, and build the cult arround that. Bear in mind, however, that once that magic is integrated, the number of breakthrough points gets added as experience to an appropriate skill. That might be a supernatural / arcane ability, but it can also be a new mystery cult lore skill iirc. The integrator needs no script to open those skills to himself, but may need a script to teach others. I'd have to re-read the rules to see if the script is developed as part of the ancient magic integration giving him experience towards the mystery cult lore or not. If it's not officially part of the rules, I would lean towards leniency as a storyteller and work with the player to develop a script that makes sense considering the experiences he went through and the kind of cult he wishes to build in order to let him initiate others.
If it is integrated it no longer requires a virtue to use. If it has been discovered that is a separate issue, but simply integrating a non hermetic hedge tradition into the order via e miscellanea adds new virtues to the collective pool of virtues within the order, so this boundary feels artificial.
On the other hand, how would a mystagogue even know about something like fertility magic to decide to initiate it...
Unfortunately, the game uses the term breakthrough and integration for two different systems, one being ancient magic integration which is really the search for the breakthrough, and the other being the process of Hermetic integration that can follow a successful breakthrough from original research, so such conversation about the two systems can sometimes lead to confusion... Ancient magic that has been integrated explicitly relies on supernatural virtues and mystery cult lore initiation. It has not went through a hermetic integration yet (and probably won't, unless a Bonisagus is leading the research).
I'm not sure he could. It's "easy" to say, I want to initiate a magical focus on XYZ, because a magical focus is something that is fairly well understood and so a mystagogue would start thinking of actions or quests that resonate with the type of focus that is sought. If the end result is not actually understood, I'm not sure it can be initiated. For starters, the mystagogue probably wouldn't know whether he's initiating a minor or major virtue. The way I understand things, many mystery cults drawing on mystery virtues from TMRE or HoH:MC are probably the result of ancient magic integration system, whether that's recreating a lost tradition, or learning from a being of magic or faerie might.
Yes. Bearing in mind, however, that Supernatural virtues tend to rely on ability scores, and sometimes foreign arts. For the example of the Fertility Magic, I think we have two issues for a pure mystery approach: First, not knowing what the end result will be. Second, fitting that end result into hermetic theory. To take your example of the mystagogue looking to initiate some form of fertility magic, well ex Miscellanea has the Control Fertility virtue. However, this Supernatural virtue works as a stand-alone system, not with the hermetic system. You can use it to ensure conception will occur, but you can't extend that system to design the virtue combination the kid will be born with by checking up your CreoCorpus lab total. A mystagogue probably could very well seek to create an initiation for that virtue. I don't think he could do the same with the end result described in Ancient Magic, unless again, you as a storyteller decide that this magic already exists, instead of being an example that could come out of a pet research project generating insight into a lost tradition of magic to bolster magic theory.
My take on it anyway.
In the same way as the ArM authors did. They imagine it, and then they negotiate with the editor, sorry, the deity, to grant it.
A Mystagogue of an existing Mystery Cult needs a new Initiation Script for that Cult to initiate a new Virtue.
Such a new Initiation Script needs to be either adapted from an existing Script (see LoH p.49 box Borrowing Cult Lore and Initiation Scripts) or invented from whole cloth (see TMRE p.18 Experimental Scripts). Both require, that the Mystagogue has researched the Virtue in a way accepted by troupe and SG, but does not need acquired AM p.8 Insight.
Self-initiations to Virtues with existing Initiation Scripts for a lost or foreign Cult Lore are described in exemplary fashion in LoH p.46ff Fortunata's Island of Bound Spirits. Using Experimental Scripts is more risky and requires more judgement calls by the SG, but is also possible.
Given that drawings on a cave wall are unlikely to be initiation scripts, I think it comes down to "researched the virtue in a way accepted by the troupe and SG" which leave s lot of room for variance.
It is unlikely, perhaps, but there are ways to do that as a storyteller if your game would benefit from a mystery cult approach to avoid the process of ancient magic integration as a storyteller. Maybe a hunting ritual depiction that shows a feast has a few stars in the sky to represent a particular time of the year during which the initation must occur - the part of the year that constellation can be seen, something a player could identify with an Int+Artes Liberales (Astronomy) check. Maybe another mural represents the animal of virtue you must ritually sacrifice. Maybe a third represents how the sacrifice must occur over a huge bonfire with ritual dancing. Maybe a fourth mural shows peaks that can be correlated with a specific place where the ritual occurs with a successful area lore check. Maybe the fifth mural in that cave system depicts an ordeal. And together, they form a script with speficic time and place (+3), an ordeal (+3 to +9), a quest to capture an animal of virtue (+3) and an unknown sympathetic bonus which could depend on how well the magi succeeded on his lore checks and interpretation of the murals. Because visual depictions might be less reliable than a written one, you could consider the whole thing an experimental script where the mystagogue is unsure whether he has enough script elements to self-initiate. You could choose to let the player initiate using an existing mystery cult lore, if appropriate, or you could decide to use the fertility relics and murals as significatos and realias rather than a source of insight, if you wanted to go down the route of mystery cult initation and not the breakthrough approach.
I don't give access to Virtues that need to be researched unless they've been found/researched/etc. Same thing with things like the Personal Power Virtue. Otherwise you could just ask your local Gruagach or Learned Magician or similar to just grant you whatever cutting-edge Virtue you'd care to design if it fits into the categories they can provide.
We need to draw a distinction between rule systems which absolutely allow for this, and RP which may not. RP is I feel the big difference between the two. ANY researcher, no matter their interests can use hermetic research and ancient magic integration to get any virtue.
Mystery cults though include systems of belief and practice. So the first question is "Does the system of belief and practices of the mystery cult lend itself to being able to develop this virtue?".
If I had a Cult of Hades in my game, I'd allow pretty much anything to do with spirits, ghosts, theurgy, all that good stuff. I'd be super reluctant to allow a member of that cult to develop hermetic astrology with their Cult of Hades lore.
So its not just about having a massive presence and cult lore to self initiate a virtue, its about also having the right cult lore for the virtue.
The idea of self initiation through cult lore though is excellent. At high cult lore scores, your character is basically a paradigm of the cult practices. They are so thoroughly steeped in the way the cult sees reality that its entirely possible that they might engage in some epic initiation to open themselves to the possibilities of the universe. It should be played as a moment of high drama, akin to Odin on the tree learning the runes. Involvement with gods or spirits could well play a spontaneous part (cult paradigm dependent obviously). The GM and player should really be working together to craft something awesome (and the GM should really keep some details back from the player to make the RP more fun). Rope in the other players to play bit parts in the ritual.
So to summarise, I don't think a character should consider going into a cult with the idea of self initiating a particular virtue at some point. Thats putting the cart before the horses. If a character wants to lern a certain magic, then have thm either search other a mystery cult that already practices something similar, or have them do research/integration.
But when they've mastered everything the cult has to teach, when they've become the 10th level secret master of the Sacred Brethern, then they might cast their mind out to wonder what else the universe can teach them. They can undergo terrible initiations to learn new lore to share with the cult. But this should be the HARD way to do it.
A character probably should not. A player might though. The player who does should, however, make sure to narrate the quest with sufficient detail to make it worth-while as a story. If it is easy, it is boring.
The character may go into the cult to gain a virtue which the cult does not actually know, simply because he has a very approximate understanding of the Cult's power and think that they know different things than they actually do. After all, Cults tend to keep secrets/.