So this is a bit of an incomplete idea for a homebrewed Hedge Tradition, that I've been brewing around the Ars Magica Discord (and many thanks to all of you in the Discord that I've been able to spitball some ideas).
Ostensively they are very much inspired in the Faceless Men from A Song of Ice and Fire, but giving them a Mythic Europe spin, which changes their core motivations and trying to make them more in line with the setting.
Their origin is in the islands and villages around in Veneto in particular the Venice lagoon, in a Benandanti Tradition, which is a rural folk tradition, where certain members fight periodic spiritual battles in Nightwalker form against other spiritual foes, where the result of these battles is said to ensure the prosperity of their communities (good crops, good fishing, etc.). However as Venice became increasingly important and sophisticated, by the time of the 1200s it is a quite strong maritime power with many of the things that we associate in popular culture with Venice (the Carnival already exists in unofficial form, while the earliest mention of masks seems to be in the 1260s, it's probably fine to have a bit of anachronism here). They've also reaped plunder from the Eastern Roman Empire as a result of the 4th Crusade.
So my idea, is that this is a tradition that eschewed it's folksy traditions and now is a Venice based tradition that instead of fighting nightly spiritual battles, they metaphorically fight for their Republic using far more subtle methods of intrigue and information gathering, subtly influencing politics, trade and using covert methods to ensure the prosperity of the Republic. They are not necessarily loyal to a particular Doge or family, rather they are loyal to the idea of Venice itself.
They are mostly an unGifted Hedge Tradition with some Gifted individuals, working more like a mystery cult, loosely organized but united by a common goal and set of practices. Due to their "masters" being Gifted, they act more like a collection of cells which can cooperate, but occasionally can oppose each other, as although having the idea of prosperity of the Republic as their unchangeable goal, they may have different ideas about what that means and how to accomplish it (e.g.: maybe groups differ in opinion who is the best candidate for the next Doge).
Due to their very nature as a Mystery Cult (as as we'll say later their Warping response) and their lack of Parma, it's impossible for them to actually become a very strict organized group. So think of them more like a culture within Venice, rather than necessarily the masters behind every plot.
I've named them L'Incognito (venetian language for "the unknown) and they mechanically are like this:
Favored abilities: Unveil* (new supernatural abilitity), Persona (from HoH: S), Magic Sensitivity, Second Sight.
Most unGifted members of this tradition will have only one or two of the abilities, typically Unveil and Persona, which are their signature supernatural abilities.
They have initiation scripts for their un-Gifted members to initiate atleast Persona and Unveil. Gifted masters who advance in their Mystery lore can know (and create) scripts to initiate these Mystery Virtues. Commonly these scripts will inflict a major or minor personality flaw Driven (Venice prosperity).
They can Open the Arts for a Gifted candidate which gives them the favored abilities Persona, Unveil, Magic Sensitivity and Second Sight.
UnGifted characters can be generated as Companions, with the apprenticeship package, balancing Virtues and Flaws to get access to this traditions supernatural abilities. Personality Flaw Driven (prosperity of Venice) or something to this effect would be almost universal.
Gifted characters can generated as normal, where they get this traditions Favored Abilities without needing to buy Virtues, but they get a free Major Non-Hermetic Virtue that can be spent on Ways of the Land (City or Town), Mythic Herbalism or possibly as it may fit the character some other Major Non-Hermetic Virtue (for example they could earn Wealthy as part of the apprenticeship, the master introduces to contacts, helps them set up a business, perhaps inherit from a Persona of some other member that needs to pass on to be credible). They also get a free Minor Non-Hermetic Virtue and an obligatory Minor Personality Flaw Driven (Venice prosperity). Different groups of this Cult, may differ in methods so feel free to be flexible here.
Their apprenticeship typically intense, 6 years for 150 xp to be spent in their ability, independently if a member is Gifted or unGifted. Normally Gifted members are picked up early in their life, but suitable unGifted candidates may be initiated later on in life. The apprenticeship focuses not only their favored abilities but also in the general social skills and whatever skills may be suitable. They focus a lot on understanding human nature in general, seeing and being aware.
A L'Incognito is supposed to have a cover identity, which they use to support themselves, which they need to work for two seasons (subject to the Poor flaw or Wealthy Virtue). If the apprentice is young, they typically for a few years are supposed to work on their own to support themselves and establish a useful niche in whatever community they are based on, to see how they can put their skills to good use.
The Unveil supernatural abilities works as follows:
Minor Supernatural Virtue: Unveil (“Verxar” in Venetian from “to open”). This grants the supernatural ability Unveil at score 1.
Unveil: This ability has 2 effects, passively it adds to Folk Ken rolls (like Mythic Alchemy adds to Philosophiae), when engaged with conversation with the target. Refer to the rules on HoH: TL, pages 24 and 25 on how Folk Ken can be to used to ascertain deception and perceive the target’s motivations. Note that this effect counts as natural magic (in Hermetic terms, it would be more like the personal Rego Mentem effect that allows to concentrate on a specific task), so it's not subject to Aura Influence nor does it need to penetrate.
This ability can also be used more directly at Eye Range, on a Per + Unveil roll for the following effects. It is a Magic power, subject to aura interactions. Beings with Magic Resistance get their Mentem magic resistance and if the subject is aware, they can try and resist on a Int + Concentration roll of Ease Factor 9+.
Ease factor 6: Determine the dominant emotion of the target
Ease factor 9: Determine all emotions of the target. Discover if a statement is believed to be true by the target.
Ease factor 12: Pick out the most relevant word or answer regarding a statement from the subjects mind.
Ease factor 15: Read the surface thoughts of the target
They are interested in Supernatural lore and while they have no direct uses for Vis, they understand its importance, especially when used as currency in the supernatural world or how certain vis can have other properties. They also understand and try to find lacunae or magic/faerie auras in the urban settings they mostly operate on as they understand it can facilitate entering and exiting the Personas they assume and they know they are important to other magical traditions. They know about the Order but probably not much.
While they'd not be a scholastic tradition, almost all of them would be literate in the Venetian vernacular as they probably find the concept of written ciphers useful.
Their methods should be very subtle, they are good at influencing people and finding secrets and can use covert methods (planting evidence, stealing, sharing of select information with rivals, even assassination using poison or "accidents"), but I don't think they're nakedly powerful (even compared to other Hedge Traditions), so they're probably not antagonists that would be near the level of the Order, but they could be tricky in Venice or whenever Venice interests lie in Urban Areas. The kind of stories they might be interesting I feel are more cloak-and-dagger intrigue stories in the mists of a Venice night.
While they are not favored abilities, Mythic Herbalism, Animal Ken, Entrancement, Lesser Craft Magic could be typical abilities sometimes found in this cult (they are descended from rural and folk practitioners but they are now sophisticated and practical) and some groups could at discretion be able to initiate them.
I haven't yet fully thought of their Warping Response, but I feel like it should work mechanically like a the Witches Moon (in the sense that it's a result of increasing warping score, not just getting two warping points) and would amount to something like they gradually lose personality traits or become locked into their Personas temporarily or eventually their identity can fragment into their Personas, where there's a common motivation but the specifics of plans become fragmented into different Personas).
I haven't fully thought also that mechanically, each Persona identity they could create, could be Mastered by XP points, where one could create some effects like the Persona having some useful virtues like Venus's Blessing, Forgettable Face, perhaps something like a skill Pretense to make the disguise more believable, perhaps a way to make them harder to pierce with magic.
Well, sorry for the long text, I hope you may find it interesting and I'd love to get some feedback. I've tried to balance things, but of course I haven't playtested this yet so tweaking could be necessary. Feel also free to change parts of this idea as you feel like, nothing would make me happier is something silly I've written ends up in someone's game :). They could easily be dedicated to a Faerie or Magical Genii Loci of Venice (or some other place) or even written as an Infernal tradition or perhaps a more scholastic conspiracy using an offshoot of the Mathematici with Persona.