Although you need to be able to sense what you are affecting with Hermetic magic, you don't need to sense your Target in its entirety.
This leaves, I think, opportunities here for Stories with Boundary (or even Structure) when a wizard doesn't walk the Boundary they're casting. They might be surprised when the spell includes or excludes parts of what they thought was the Boundary but maybe didn't fall under the same sympathetic connection to the part of the Boundary they'd sensed to cast it. Imagine the embarrased Tytalus who at an inopportune time discovers that the new garderobe he built on to his wizard's tower a few years ago wasn't in the lazy Boundary of the covenant's Aegis. Or maybe the covenant's lazy Aegis included some caves connected to the covenant's labyrinth that are inhabited by some faeries who suddenly find themselves "natives."
My own magus has had to plan around something similar for the "not sensed in its entirety" problem with Hermetic magic as he's inventing a ritual to create a road 273 miles long. Obviously, he can't sense the entire thing but it would be obnoxious to yank the entire purpose of the ritual by making it go to a random destination or something, and too onerous to make him have to walk the entire distance as part of casting the ritual. Our troupe has agreed that he can have some influence over it by using sympathetic/Arcane Connections of what he wants... but that the details will maybe be awkward.
Hopefully, he won't send a highway through the middle of someone's cottage (not too likely; it's mostly through wilderness). I don't know if an entire Story will come out of this, but there'll certainly be some interesting flavor from it. Same should go for casting a Boundary ritual without planning for it, I think.
People tend to over estimate the hurdles of high penetration
Say you have a healthy Aegis 40 with infinite penetration (academic purposes only ;p ) and you are within it as a foreign agent thus start your day at -20 on your casting total
Basic Casting Total
Te (10) +Fo(10) +Stm (2) +Aura (3) +stress die(5) = 30
The Extras
Talisman (5), Artes (3), Philo (3), Penetration Skill (3), Mastery (4(2) - Ceremonial casting & Penetration), MF (10), Other Merits (10), Vis (40), AC from Boundary (x4 = 12) Total = 90
Lets divide the extra's in two because rarely will a magi have all of those extras 30 + (90/2) -20 - Level of effect (20/4(Communion)=5) = 50 penetration total and dispel the foreign Aegis. Almost any senior Magi can muster those numbers.
In a paradigm where we can dispel easily the Aegis and that Aegis is used as a form of siege weapon, a covenant probably has atleast one member with the ability to dispel an Aegis as above.
In my typical campaign settings, we usually have the HR that it takes a ritual to dispel a ritual & the PeAegis/PeParma are outlawed except for Guernicus & Hoplites in good standing... and villains of course. Still leaves all creatures that have a good understanding of hermetic magic of Duke level and above (Might 30+) that can dispel a typical Aegis of their might or lower with a snap of their finger. In there we have some Angels, Demons, more and more Jinns as they learn about the order of Hermes, Past Magi that have turned to the side of creatures such as Fey or Magical beasts or Ghosts.
Which would imply that the legitimate AotH would be an AC back to its casters.
Suggesting that an enemy magus need access to the AotH boundary to hit the casting magi with Arcane Range spells. Though they may have to wait until the target magus is outside the AotH to cast these arcane range spells with descent Penetration.
It may interest someone what we ended up doing in my campaign as the players realized that Aegis is pretty darn tough. As I had ruled you cannot get an arcane connection to it unless you have a token (it's intangible and designed for defense) penetration becomes really hard - basically the purpose of the Aegis. After all it has stood the test of time in the Order.
This is not really per RAW, but we had to figure out something as the players needed to overcome first a level 30 aegis, and later on a level 40 in order to deal with "a couple of things" inside - as players must :).
They realized they couldn't figure a solution with regular spells or counter rituals. However, a charged item - by planning ahead and spending a season of lab work (by a Verditius, with specialists assisting) they could get some quite high PeVi totals.
What we ruled as Levels required for basically a "temporarily suppressing an Aegis effect":
Base Level 10
A Casting Bonus equal to the level of Aegis (to even be able to attempt activation), i.e. 40
A penetration exceeding Aegis, i.e. +21 Penetration gives 42 in Penetration
+5 Touch
+10 Sun to have some time to operate (note: I've been ruling out concentration and device maintains concentration for charged items - else that's an option at same cost).
If I felt nasty, I could have ruled another 20 for "Boundary", but I didn't - because this was more interesting for the narrative.
They needed 86 Lab Total (91 bumping it to Moon) and I required experimentation to develop it, which cost them a lot of time and came at some interesting risk. (and if you wante to, you could require a "Discovery" to work it out - it's not really standard magic in the Order)
When on the cusp of the total, a decent roll will net one item, a good one two or if real lucky 3 (as per regular charged item rules). These are one-shot, and will only suppress an aegis for a limited amount of time (more fun and stressful).
Why is it temporary? PeVi here is just "dampening" and not dispelling the effect (would require ritual and a quite different approach - not convenient on-site) and therefore needs duration. We could consider the Aegis is "powered" by the vis at it's annual casting, so as soon as PeVi effect can't counter it, it fills out fully again.
Again, not entirely RAW but it worked well for us.
Of particular note is that this troupe is not quite fresh out of their gauntlets, the campaign is on session 131 as they're doing this vs an Aegis level 40 (they defeated the level 30 just a little before session 100) and have had to invest over time to achieve it.
B10 + 1 Touch, +2 Sun +21 Pen = Effect level 46 x2 for Charged Item = 92 & you create one charge of the effect but in the next season you create 18 of them using the lab text.
Ah.... been a while since I looked as Verdi... they have something to lower the lab total requirement I guess.
Still, That Verdi will never forgive you for publicly advertising that he wasted his time working on a trinket. At least he can save face by bragging about how much profit he made to his peers...
A bit less of an insult would have been to create a Major Item & to use effect expiry. He would only have had required 51 of lab total, a few pounds of vis and two seasons instead of one.
Note that the "villains" that control the Aegis could have simply dispelled your Aegis suppressing effect with a level 20 PeVi effect which, if they also have over 100 seasons of wisdom, can probably be sponted.
Like I said, we weren't going exactly RAW (it really has no good rule for this IMHO).
This is for a number of reasons, including narrative, and after all it being the "special" semi-hermetic spell Aegis being affected. Aegis is supposedly designed and hardened against interference, and also quite non-replicable (major breakthrough!) - it really is a special spell!
For this reason, the base and level isn't the same as for other PeVi. Base 10 (sheer complexity, and it's vs a ritual), + unlike regular PeVi to dispel effects where you get 20 levels + simple die leeway vs a higher level, this doesn't make sense the same sense for the aegis. It'd make sense that you might need the full 40 levels (8 mags).
In addition, the next logic is that technically you'd have to penetrate the Aegis itself from the outside to affect it (not inside, as you're targeting the aegis itself - but you can rule different ofc). E.g. >40 penetration.
E.g. the effect needed i very high: 10+40+21+5+10=86
This is ofc ritual territory if it was a regular spell - but Charged Items is the system "shortcut" (which I'm a bit skeptic about but here we are) and this is also where you can bypass the level 50 cap for non-rituals (another thing I'm a bit ambivalent to).
IMO: It should require a bit of a feat to defeat the tried and tested Aegis protection.
--
If you do this as per RAW (which feels incomplete), you could get away with (help me out if I forget something:
No Base
Since you know it's ReVi effect, utilize the RAW guideline of "Dispel effects of a specific type with a level less than or equal to the level + 4 magnitudes of the Vim spell + a stress die (no botch)." For an Aegis of 40, with a bit of gambling (50/50 chance with stress die) you could make this simply level 15!
+1 touch, +2 sun and you are at simple level 30 effect, or just do Concentration for less (not even the Aegis, meh).
At least one of my magi can manage to spont that level of effect in decent conditions (but perhaps not penetration that high).
Making it formulaic solves it. By RAW I think it's enough with just a generic PeVi that targets any ReVi effect (to not halve the required level). RAW is missing quite a bit here IMHO.
However, you'd still need to penetrate so after all a bit trickier. From outside it's the plain 40, but if you have good casting total on a formulaic and arcane connection it's very doable (too easy for comfort IMO).
If you allow it from within you only subtract 20 from casting total (so maybe not spont, but reasonable with formulaic), and Penetration. If you allow an arcane connection, and/or some sympathetic connections that becomes simple journeyman level challenge.
I don't think anywhere RAW the aegis have protection against manipulation more than this (correct me if I missed that).
Anyway, still requires a decently competent mage for formulaic. But I'd argue barely on par with the level of competency required to cast the aegis itself.
But the cheat-code that's charged items becomes even easier. Just add the +21 for penetration (Which is so CHEAP for items frankly) and you're at 51. Even fledgling Verditius (and some out of Gauntlet) can do this with prep, help and materials. Fairly simple for other Houses too frankly. Fairly soon they'd also make dozens per season - and very cheaply at no vis cost. Everyone would have a few spares of this "just in case" and no aegis would be safe. This is why we went non-RAW.
Actually by RAW, you probably don't need to think the same way - you could just kill the spell - so no duration needed. e.g. reduce the levels in my example by 10. Zip-Zapp easy.
(I'd still rule differently but anyway).
By RAW, Perdo Vim dispels an effect permanently, it doesn't temporarily dispel it. Temporarily lifting a spell falls under Rego Vim and it's complex: Sustain or suppress a spell cast by another with level less than or equal to half the (level + 5 magnitudes) of the Vim spell.
Yes,which is why the Aegis needs house ruling to be tougher. It should only be dispellable with a ritual. A ritual that takes time and can't be more than voice range.
That's the way we play it, to the point that it isn't practical to crack a high magnitude Aegis by anything like conventional methods. It's not just a matter of generating a high total.
Ah the good old days when you had to plan ahead to bring down the aegis.
Here were some plays
Apprentice rebel that disturbs the renewal
Meddling with the boundary
Wizard war the caster of the aegis to stress him out or even have him no show
Attack during the ritual
Defenders also knew how vulnerable they were on that day... Now anything can happen on any day and will always be a simple PeVi formulaic with a bit of vis if needed.
Ironically, the change was made for the betterment of the story
If this was a comment on my (admittedly non-RAW) usage:
I agree with PeVi = permanent dispel when used against actual spells and not "temporary", but as any spell - PeVi spells can also have duration. This is to either suppress a magic effect - or to dispel continuously. This is by RAW.
So I would argue that in this case, here you could see it as two choices.
Dispelling the spell outright. This should be HARD, at least specifically for Aegis. RAW doesn't really cover the use-case at all which is a bit disappointing.
Dispel the magical effect emanating from the Aegis spell - perhaps only for a specific person (e.g. only personal spells working), or on the boundary as a whole. I.e. supressing (as was suggested). This should be easier (at least for Aegis). There are several examples of spells that do this for other magical effects, and using a duration (in ArM5 core, Masking the Odor of Magic is the one example), so I'd consider it to be a usage that's within reason in RAW.
Additionally, the Aegis is technically not fully hermetic, and it's a year long ritual powered by the vis from casting it. As such, it makes a kind of internal sense. You can "permanently dispel" the effect momentarily/continuously but the moment you don't it's back on - powered by the ritual (if you didn't dispel it). And for sure by RAW would require a ritual to dispel. This equals RAW when it comes to "Odor of Magic" and similar things. Odor doesn't become permanently destroyed.
Yes, it was a comment on your usage. And yes, Perdo spells can have a duration. Perdo Vim, however, does not suppress as far as I can tell - or at least not in the sense of temporarily lifting the effect so it can naturally come back after the PeVi spell expires. Suppressing an effect so that it comes back later is what Rego Vim is for - the techniques don't overlap. That's why I quoted the base effect. If you believe that Perdo Vim can merely suppress as per RAW, can you provide a quote? To the best of my knowledge, Perdo Vim with a duration does what other Perdo spells with a duration do: prevent what was destroyed from returning. So a Perdo Vim targeted at an aegis with a sun or moon duration would try to dispel any other aegis that was put in place during that time period. Whether it could do so without also being T: Boundary, I doubt it, because Perdo Vim spells either need to target a spell or a regular target... and if they use T: ind to target the aegis spell... chances are that specific spell isn't coming back whether a new one is cast or not.
By RAW, what you're looking for is Removing the Hearth’s Keystone.
Removing the Hearth’s Keystone
PeVi Gen
R: Touch, D: Mom, T: Ind
The caster dispels an Aegis of the Hearth effect. There is no other evidence that the Aegis is absent, but alert magi crossing the supposed boundary of the Aegis may notice that they do not feel the characteristic tingle which indicates the presence of an Aegis. The Aegis of the Hearth effect must be less than the level of the Removing the Keystone spell + 3 magnitudes + stress die. This spell must penetrate the Aegis of the Hearth effect, of course. Note that if the Aegis of the Hearth is of a high level, then this spell may need to be a ritual.
(Base effect, +1 Touch)
Source: Hermetic Projects, 94
I don't mind house ruling to make aegis harder to dispel - or force the ritual, there are valid troupe reasons to consider that. I's a fine house rule for a troupe to make aegis hard to dispel, or require a ritual to dispel. By RAW, it's not that hard to dispel level-wise (but you must penetrate, which is a separate problem). That doing so is likely to make you marched or wizard war'd on by an entire covenant (and being a legal target while onsite without such a dow) is probably the reason this doesn't happen often.
So, Masking the Odor of Magic uses the base guideline "Make something (including a magical item) seem non-magical to any Intellego spell of less than or equal to twice the (level + 2 magnitudes) of this spell." It hides the effect. It doesn't dispel magic emanating from someone nor does it suppress anything (or at least, not in the sense used by Rego Vim).
One thing that's crossed my mind in the mater of dispelling Aegises is a possible distinction between "peacetime" and "wartime" Aegises.
A "peacetime" Aegis is focused on the risk from supernatural creatures; it's important for it to have as much penetration as its level, so it can keep out faeries, demons, and the like. It's nice that it also penalizes foreign magi, but . . .
A "wartime" Aegis -- and it's unlikely they've been extensively used in the Order since the Schism War -- would concentrate purely on level. Because penetration won't keep out against enemy magi, but every level of the Aegis both subtracts from the casting total of hostile magi and increases the level of spell necessary to dispel the Aegis itself.
At a first glance, this suggests a "wartime" Aegis will tend to be double the level of a "peacetime" Aegis, because if you can cast 40 levels of Aegis and 40 levels of penetration, you could cast 80 levels of Aegis. And that moves the casting total necessary to reliably take down the Aegis from outside from a 65 (for a 25th-level Removing the Hearth's Keystone plus 40 additional levels to overcome the Aegis) to 145 (for a 65th-level Removing the Hearth's Keystone plus 80 additional levels to overcome the Aegis), while making the takedown spell a slow-casting, vis-consuming ritual.
The biggest barrier to that level-doubling is inventing/learning the high-level Aegis. Even with a lab text to follow, it's a lot easier to get a ReVi lab total of 40 than one of 80. And without a lab text, it's much much harder to finish a 80th level spell in a reasonable number of seasons.
This creates a certain sociological effect in the Order. In case of a new period of anarchy/war, relatively young covenants in most of the Order will be very vulnerable to their Aegises being taken down. It would suggest needing the favor of an older ReVi specialist who can assist them with their Aegis casting or provide a very high-level casting tablet. But in places organized like the Tremere-dominated Transylvania Tribunal, one can expect many oppida will be systematically reinforced by the House/Tribunal dispatching specialists (if only to the ones the senior magi of the House/Tribunal think are worth the resources to reinforce) or casting tablets.
While we might not agree exactly on how we see Perdo, you make a lot of sense here. Thanks for weighing in - it's thoughtful.
Also thanks for pasting that. I was wondering where the "kill Aegis" spell was hiding when I was searching for the effect I either found it and didn't like it - or I didn't (I don't remember frankly). Anyway I had to on the spot come up with an alternative (hence non-RAW from above). Really should be in core IMO.
Interestingly it's not a ritual and would have somewhat derailed my campaign if the Verditius got it that easy for charged items (which I may also have to house rule nerf for next time).
As you highlight, it does come with interesting societal implications if it's fairly easy - especially if you allow the slightly easier modifiers from within an Aegis. As called out, it's all about the reason for the aegis dispelling. For the Order, it's an interesting observation that it's much more likely the threat of marching controlling it - and it'll be an expected factor in Wizard's War between covenants (where other measures are expected to be taken anyway).
There are some very specific circumstances in my saga, that's not straight about the Order that led to the need there (ancient Diedne magus cursed to be faerie, with a bit of an agenda), so I might be a bit colored on the use here.
Regardless, I do think the +3 magnitudes here might be too easy if you allow any multiplier increases of Penetration. It's a bit weird it's designed as so low. At least one of my players could likely spont this one for the level 40 aegis with some prep if he could just get x2 or x3 multiplier somehow (todays horoscope on site, representation etc if you'd allow that). Definitely if an arcane connection could be had or ruled.
Well, "Removing the Hearth's Keystone" is the core rulebook's "Unravelling the Fabric of (Form)" with the range reduced from Voice to Touch, the magnitude so saved added to the level of spell it can destroy, and the effect made less general. So it would not be perfectly redundant, but . . .
Also, there's now a free official PDF of all published Fifth Edition spells.
Even if RAW, there are problems with the spell as written IMO.
It does not take into account it's a ritual nor the aegis not conforming to standard hermetic theory. That should warrant at least a complexity increase, if not an outright ritual itself.
If allowing touch, I'd argue you'd at least need to touch the actual "Aegis Keystone" (if there is such a thing anchoring the magic). An interesting idea this really could be an anchor item in the ritual, which then should be additionally protected within a covenant. Not just touching the "nothing" within the boundary of the Aegis. I know it's handwaved like that with other spells, but not always - Ars Magica can be a bit inconsistent :).
In the case of the dispel, I'd argue you'd need boundary, or at the very least voice.
If the aegis can be dispelled that easily, so can the Parma? They have the same root after all.
PM can be dispelled with a simple PeVi spell. Even Wind of Mundane Silence from the core book can do it. And then there are Break the Shield (HP p.85) and Revoke the Protections of Bonisagus (F&F p.71).
And yes, Perdo spells can have a duration. Perdo Vim, however, does not suppress as far as I can tell - or at least not in the sense of temporarily lifting the effect so it can naturally come back after the PeVi spell expires. Suppressing an effect so that it comes back later is what Rego Vim is for - the techniques don't overlap. That's why I quoted the base effect. If you believe that Perdo Vim can merely suppress as per RAW, can you provide a quote? To the best of my knowledge, Perdo Vim with a duration does what other Perdo spells with a duration do: prevent what was destroyed from returning. So a Perdo Vim targeted at an aegis with a sun or moon duration would try to dispel any other aegis that was put in place during that time period. Whether it could do so without also being T: Boundary, I doubt it, because Perdo Vim spells either need to target a spell or a regular target... and if they use T: ind to target the aegis spell... chances are that specific spell isn't coming back whether a new one is cast or not.