I may have missed a rule somewhere but it looks relatively easy to remove an entire Aegis of the Hearth using Unravelling the Fabric of Vim. Please, someone correct me if I'm wrong.
Unravelling the Fabric of Vim will undo the effects of one spell whose level is less than Unravelling level + 10 + d10. Assuming an Aegis of level 25, an Unravelling spell of level 10 would have a 50/50 shot of matching its level. Assuming a magus could pull off a PeVi casting total plus penetration of 35, the Aegis would be dispelled.
That does not seem like much of a task even for a relatively young magus.
That's not exactly how I interpret "whose level is less than Unravelling level + 10 + d10." You have to compare the level of the Unraveling spell (bonus included, granted) not the casting total, with the level of the targeted spell, to meet the condition/unravel the spell. So, the way I read it, the level of the Unraveling spell would need to be at least 35 (pending a 5+ roll on the d10)
Besides, even in your example, it seems that you forgot to reduce the casting total of the Unraveling spell as per the usual rules of Aegis, by half the level of the Aegis, 13 here.
I disagree, the original poster is correct. A level 10 Unravelling the Fabric of Vim dispels any Vim spell of level less than 10+10+1d10=21-30. This is also consistent with the guidelines.
I believe the original poster assumed implicitly that the spell is cast on the Aegis from outside the Aegis, so the penalty does not apply.
I would point out that in previous editions dispelling an Aegis was much harder; in general, one needed Ritual magic to dispel Ritual magic. As it is, it's indeed very easy foraHermeticmagus* to take down an Aegis.
One thing to bear in mind is that the spell guidelines assume a default Personal, Momentary, Individual. If you change the spell to Touch, Momentary, Individual (one magnitude higher) then your level +10 actually becomes (level minus one magnitude) +10 (I think). So as you extend out to voice/sight/arcane connection the efficacy of the spell gets less and you need a higher level spell to have the same effect.
However the specific numbers work out though, you're still right though that it's a relatively easy thing to do in the long run, especially if you spend some time in the lab to create a dedicated device or even some one-shot charged devices - better yet, support your local Verditius and get them to build you a device. They won't ask questions and you'll always get a good deal.
First, the text of Aegis says "If the foreign spell cannot penetrate a resistance equal to the level of the Aegis it fizzles out."
Analyzing it, as it pertains to your example suggests that to have an automatic shot at taking the Aegis down, you need a 15th level Unravelling (10+15+0 [assuming a 0 on the die roll]=25), and you need to be able to cast it with +26 penetration. That means a PeVi CS of 40 (assume a die roll of 1, non stressed) to make it automatic, or something that will help you with penetration. If a Magus is going for something like this, they want it to be automatic. If you mess up, well, imagine a bunch of Magi popping up and going Scarface on the perpetrator of the attempt. "Say hello to my little friend."
And this only gets more difficult the higher the level of the Aegis.
Actually, the main limitation appears to be targetting, in that you must be able to target the Aegis.
Usually this means you have to be able to see it, but there's no indications that the Aegis itself is visible - you'd need InVi to do that.
HArdly insurmountable, but that's about it.
Already taken into account - Unravelling is a spell, already at R: Voice.
Compare to the guideline please, the level refered to is the level of the spell, as R: Voice has - again - already been "paid for".
Nope, sorry - you still have to be able to sense a target to affect it with R: Voice spells - ArM5, p. 80, Limit of Arcane Connections.
Gruagachan may violate this (R: converation IIRC). Breaking this is suggested as a possible integration effect.
So no, word carrying 15 just aren't good enough.
Okay. So, following the majority's consensus, np, let's say that a magus would re-invent a Range:Touch version of 'Unraveling the fabric of (form) (instead of Voice/Mom/Ind), still choose to keep it at level 10 though. If we allow Voice range to target an Aegis, why not allow Touch for a magus touching the boundary of an Aegis (that any magus can sense as a tingling even without InVi magic), I don't have a problem with that last point.
Then he'd get an unraveling formula of :
10(level) +15(instead of +10) +(0-9), potentially unraveling Aegis of level 25-34. Right?
Since he has to penetratre the Aegis level, he would be able to cancel an Aegis of level 25 with a casting total of 26, or a CS of 31 against a level 30 ; the former, I beleive, being rather customary for Spring covenants.
Assuming a recently Gauntleted magus moderatetly focused in PeVi (sta+1, Pe 8, Vim 10), since he'd probably get the benefit of the Aura, say +3, he'd need a roll of 4+ to his casting total, to put down the average Aegis of a Spring covenant.
But since any magus not too hot-headed would probably not goes against a whole covenant as just "recently Gauntleted", I'd say that we could expect a better CS for such hostile endeavour.
What's bothering me here, and I don't know about you guys, is that considering all this any magi forming a new covenant should actually not even bother wasting vis in a Aegis.
Penetration is the amount in excess of the die roll, which may be subject to multipliers or additions due to Penetration skill if ACs or sympathetic magic can be brought to bear on the Aegis. So, for a 25th level Aegis you need to get to a CT of 41. 15th level spell +26 in excess of spell level.
Pixies, imps, ghosts, elementals and any number of angry or bored spirits, sprites and minor magical creatures and hedge magicians. The aegis is not necessarily an unbreakable wall that will protect your covenant from any magical attack as much as it is a basic safeguard. Having an aegis is much the same as locking your house door at night... it won't keep out a determined invader but it will keep out a casual house breaker.
The underlying point still stands, I think. Is it easy? Relatively, yes. Do you need a ritual? No.
The discussion usually ends up with the claim that it probably should need a ritual to dispel ritual effects. I'm not sure I've seen that anywhere in the fifth edition rules, so it doesn't. And as for game balance, as far as I can see it, the only ones likely to be disadvantaged by house-ruling the ritual requirement are the players, so I wouldn't do it in a month of Sundays.
Thanks. Mark's original post put it in perspective for me. If someone is attacking a whole covenant, then taking down an Aegis is the least if his worries. Attacking such a fundamental pillar of the Order seems like an attack on the whole Order, so unless you have a rock solid reason for doing so, in my saga I would expect to get wizard marched for it.
Makes me think about my own Aegis differently, as per Lucius' post.
Exactly, the Aegis is largely there to protect against supernatural threats that are not other magi. It's not really for dealing with determined Hermetic foes. Of course, messing with another covenant's Aegis would likely be considered a High Crime (unless you are engaged in Wizard War against the inhabitants, or similar).
The other critical thing to remember is that the Aegis protects everyone inside --- i.e. all the coven-folk. Usually, a magus, personally, is about as well (or often considerably better) protected by his Parma Magica. However, without an Aegis, a covenant will have massive problems with the coven-folk being possessed by demons, tormented/replaced by faeries etc.
Decide to attack a covenant wherre your rival lives. CHeck.
In that covenant there are 2 other magi not part of the WW. Check
Bring doewn the aegis. No problem.
War with rival and win. OK
Be marched for depriving the other 2 magi of their magic power. Check.
If someone did bring down my covenant's aegis with such a spell he will be laid down so hard at tribunal that his grand-apprentices would still be feeling the pain. Magi do not like you setting precedent of bringing doen their defences.