There's a lot of story seeds about interaction between covenants and the mundane authorities, but the recent talk on the Roman Tribunal's situation has got me wondering: Is it possible for mundanes to pose a significant threat against a prepared Summer or Autumn covenant? (Or even a Spring covenant, if they have a solid Flambeau on staff.)
The obvious answer, of course, is a complaint to Tribunal, but outside of Normandy or (Lords of Men's version of) the Greater Alps, if they're acting in self defense, they're pretty much clear to respond with a large-Group Creo Ignem. Which in turn does kind of imply that any story seed involving mundane authorities making demands of a covenant is easily solved with a contemptuous response, and in fact, we know that Magvillus already does treat mundane threats this way. Yet a lot of story seeds are lost if magi can respond to the threats of lords and kings with laughter and scorn. Of course, if that's the kind of saga players want (where adventures come from other powerful beings, and mundanes are only a threat at the beginning of Spring), that's fine, but not all Ars Magica players are looking for Exalted in Mythic Europe.
So. What threats and leverage do mundanes have that they can deploy against a covenant?
Mundanes can do much outside of direct confrontation.
cut off trade
Cut off/poison food supply
Prevent covenfolk from working outside the direct protection of magi
Cut off access to vis sources
Cut off access to allies
Cut off/poison water supplies
destroy/cut off access to resources outside the covenant proper
Marshall political and or social forces against the covenant
Marshall Divine/Infernal/Fae forces against the covenant
If all that fails, wipe out any ill prepared spring covenant and bring charges against the well prepared Summer/Fall covenant.
These are only the direct action options. Remember that with the "ruin upon my Sodales" clause, THE ENTIRE ORDER OF HERMES IS HOSTAGE AGAINST YOUR ACTIVITIES, SHOULD THEY CHOOSE SO Even if YOU are prepared, someone, somewhere, is not. Any you will pay the price at the next tribunal.
A lot of those threats rely on the magi's patience with the noble who's threatening, though, and their reluctance to annihilate the noble, his family, his castle, and any small furry animals in the vicinity. (I mean, is there any Tribunal that wouldn't approve of answering an intentional threat to a vis source with overwhelming force? That's almost as dumb as threatening the covenant's Redcap.) Thus my reason for asking the question in the first place.
You're right about the "and bring ruin on my sodales" part, but the idea that a noble can hold the Order hostage to wring an aggressive demand out of the covenant strikes me as a wee bit silly (though it works well for deterring magi's aggression against nobles). It doesn't pass the smell test that Tribunals would allow themselves to be vulnerable to that attack, though of course it depends; some Tribunals would consider even justified self-defense to be too much of a headache if the problem could be solved through more diplomatic means.
Realm allies do work, though, particularly the Dominion; as do matters of trade and political alliance.
Mucking with trade and such is the best bet. If the magi aren't prepared for it a army with siege engines, arches and a lot of soldiers can do a number. Remember that voice spells are out ranged by a good shot with a bow. But one thing every covenant should be prepared for is an army of mundanes. Even a spring covenant should have no trouble dealing with a stray army. Medieval armies can't hold together under fire from the sky.
Really the covenant should have no trouble dealing with mundanes who come after them. Unjustified aggression won't get a favorable response from the Divine, which is the only real worry when dealing with mundanes, if you're prepared. There is always the possibility of an infernal plot or Faerie games, but then the real issue is the Faerie and Infernal forces not the mundanes. Its quite possible your biggest worry about the mundanes would be not harming too many mundanes in the processes!
In summary, be self-sufficient, have a good group/large sized sight ranged Creo Ig spell, take advantages of wards and flight and the covenant should be able to tell mundanes to bugger off.
Bear in mind that the vast majority of Tribunals are pretty strict on the "proportionate retribution" deal. Them showing up with an army at your doorstep justifies wiping out their army (and at that point, probably letting their various rivals take it from there). Taking control of external supplies that you were more taking from them in the first place, though? Or them getting all up in your political/financial situation pretty much however they feel like? Can't be responded to with high force, not unless you feel like getting Marched.
The big things stopping the Order from allowing magi the right to conquer Europe are 1) mitigation of territorial disputes, and 2) the Divine. Especially considering the possession of the Gift and the fact that "is magic sinful" is a question even worth thinking about ever, if you hit a noble too hard, it won't matter how justified you are, the Church is now officially up in your business.
Nobles can't do jack to you. The Church? Would not recommend taking that lightly. They can mess magi up something fierce even if God doesn't directly intercede, which is actually a thing He might plausibly do, at which point you may as well just lay prostate for all the good your options are.
... Of course, rather than doing anything so crass as turning to violence, you could use a Mentem specialist, preferably one with Deft Mentem (and the Gentle Gift never hurts, but let's not get too picky, this is general covenant advice). Then your problems could be solved in a much more pleasant way.
I suspect one of the most potent weapons a mundane could have is knowledge. A 13th century Machiavelli-type that's picked up some skill with Organization Lore (Order of Hermes) and Code of Hermes could probably cause a covenant or possibly even a Tribunal quite a bit of grief. It might take some time and effort to get that knowledge, but I'd say it's doable.
It should be noted that the primary form of combat at this point versus a city or stronghold would be siege warfare, not a direct attack. cut off your supplies, fire on anyone who leaves the protection of the fortifications... and often this included archers firing from concealment in addition to siege engines with a degree of protection for those using them. You call fire from the sky and their bucket brigade will be putting out the fires as they continue firing the catapults and their men huddle under water soaked tents.
You are sort of asking how two pieces of string measure up.
Which mundanes? The local baron? A king? The Pope? A strictly mundane army? A crusade?
Which covenant? Durenmar? Castra Solis? The Cave of Twisting Shadows?
If the King of France attacks a prepared Castra Solis with a mundane army, I would expect devastation throughout the region. If a German duke attacks Twisting Shadows I have no idea what to expect.
Ars Magica is a game of consequences. Skilled magi can do whatever they want, so its really a choice of which consequences they want to deal with. Burn an enemy's armies with magical fire? That has consequences (not least: nobles wanting magi to work for them or protect them against such attacks). Murder a pesky noble in their sleep with tunnels and PeCo, or drive them mad? That also has consequences (getting accused of witchcraft / other magi being collateral damage). The question isn't "can they stand up against a noble", the question is "how are they going to do it, and what shit are they willing to take for choosing those methods over the alternatives".
I don't believe this is so. A large group Creo Ignem may cause problems for all of the other covenants in the Tribunal, which would then trigger the thereby bringing ruin upon my sodales part of the non-interference clause.
Not every Flambeau or fire expert has created large group Creo Ignem spells, their utility is relatively low. So, I would have question as to why the character is in residence in the covenant, and if he didn't create the situation where his specialized spell(s) would come into play.
Nobles can certainly conspire to make life difficult for mundane, as has been pointed out elsewhere. They can also conspire with the supernatural enemies of magi.
On the Divine side - a single prayer to Mary (doable by pretty much anyone) can one-shot a magi (Might 100, "Rebuke the Unfaithful" - change your ways or die, basically.) Sure, it's a fairly high Charm roll to succeed - but if you get enough people making the request, at least one of them will open-end.
Of course, this is the Divine version of "I cast the spell until I open-end". In all likelihood, the above scenario would be modeled more accurately as an informal Divine Ceremony of some sort. (I'd model it as a simple magnitude: take the highest possible Stat+Ability, then add +1 for every x10 people making the prayer.) Still - it's really not all that hard to get a decent roll on this one, even outside of the masses supporting you. So overt, crass displays of power are relatively easy to counter, if such actions can be traced back to the magi being jerks.
EDIT - of course, it's not THAT difficult to get 100 levels of Corpus Magic Resistance: (Parma 15, Corpus 10, Aegis 25, PeCo Spell Mastery x2) - but that means the PC will need to stay within an Aegis for the rest of their life; so at the least, it's a sort of life imprisonment.
Sure - but at least, they way I play it, Angels and the Saints are smart enough to figure that sort of thing out - so when The Templars call upon their patron to smite the evil wizard, said evil wizard actually just gets a nighttime visit in the following fashion: "Hey there, magic-man! All my little Temple-maniacs are gettin' their Crusade on for a little head-choppin' action! But you and I know it's really that heel-turn dragon up the hill! If you could take care of that, using the powers the Big Man Upstairs gave you, I'd take it as a solid. Ooohh, yeah!" (Fade to black - I like to play St. John as Randy 'Macho Man' Savage.)
Point of order: no they won't. Invoking a saint is always a simple die, so I'd say only the diplomats and saints in the entourage get a chance at it.
(Threatening the saint is a stress die, but if a lot of people start threatening in hopes of an open-end...yeah, that's asking for someone to botch.)
Mentem effect, actually, though I confess that the power is weird. I personally imagine that it's either Mentem at the start and Miracle at the kill, or Mentem at the start and a single Corpus strike at the end. However, a magus who's that well defended is not the average magus.
I would think that if magi were persecuting mundanes, the Virgin Mary could be called on to enforce a truce with that power. "Hey, stop oppressing the Christian faithful." Alternately, if the covenant were pagan (and the mundanes in question knew the difference between pagan magi and regular Hermetic practice), a nasty kick in the junk might be to command them to cease their practices (while this wouldn't work on a secularist magus, latria to an idol of Mercury is definitely an unchristian act).
I think the best weapon mundanes may have against a Covenant would be manipulation and corruption. If a noble or baron or lord or some other could potentially sway the mind of an already irritated magi?
Say, for example, Baron Nottingham is a cruel and corrupt person, and he wishes to have the Covenant down the river destroyed so he can have access to a better trade route with the neighboring country. But alas, the Covenant refuses to allow passage, so Nottingham decides to end it. Those pesky magi are far too powerful for him to take on directly, so he sends spies to both the Covenant and surrounding area, gathering information until he finds out about Gallus ex [insert any house here, but preferably Flambeau] who just so happens to be a bit corrupt himself. And maybe at odds with the Covenant already, or one of their members, or even a different part of the order.
Now that we've got the scenario set up: Nottingham could talk to Gallus, and potentially convince him that the Covenant is bad for both of them. Nottingham wants a better trade route, Gallus could want the vis sources near the Covenant. If Nottingham can convince Gallus to work against the Covenant from within....
It's an over-simplified situation, to be sure. And there are a whole host of things that could potentially go wrong here, not the least of which is the Covenant finding out about the plan and waging war on the lord before he can even start. But if the lord could use manipulation to get someone inside the Covenant to work for him? That, I think, is the best weapon a mundane would have.