Sure, with a penetration total of roughly 25. But that's not the issue you were talking about a moment ago. Your issue is that that makes beating up on other magi too easy. Let's compare that to The Call to Slumber:
Parma killer: You need a penetration total around 25 with a level 10 spell at R: Voice. Then you have to follow it up with a spell to take out the magus, leaving the magus extra time to retaliate or escape.
Slumber: You need a penetration total around 25 with a level 10 spell at R: Voice.
Parma-droppers are also less effective on any magus with a familiar because they can always fall back on using their familiar might should their parma go away. You can't dispel resistance from familiar might.
Actually, you need a Penetration total of at least 31 and more likely 36+
Why? For two reasons.
First, because you add your art score to your Parma for the specific effect, and presuming the target has a 5 in Vim is a good place to start. That puts your target's MR at 25, and forces a Penetration score of at least 26 to affect the magus.
Second, because text of the spell says you need your casting total to be more than twice (5 times Parma). So while a PeVi10 WoMS with a 26 Penetration will certainly affect the target , until you hit 31, your casting total isn't that important (5 * Parma)+1 number you need to drop the target's Parma.
While this is generally out of reach for a newly gauntleted magus, it's possible for one seven years out, presuming starting arts of Pe 10, Vi 5, a Stamina of +2 and a Penetration score of 1. After about 5 years of effort (112xp in arts to get to Pe/Vi 13, 25xp in Penetration to get to 3, 10xp for the spell, for 147xp), the magus has a casting total of 31, 32 if he specialized in Vi for Penetration. If he then spends four pawns of Vis, he hits a casting total of 40, and anything but a botch might do the trick. If the target has spent any time studying Vim, he'll need much more vis and it means he's done nothing else for the last five years, like work on his own Parma. (But that sixth year could be spent on getting his own Parma to a 3 and mastering WoMS for either multicasting, fast casting, or [most likely] magic resistance, and then the remaining time should probably be considered as spent contributing to the maintenance of the covenant over the last 7 years.)
Could you do this right out of the gate with a rook and a half of vis? Sure, but that's an extreme example and I don't think many sagas allow magi to begin with such resources-- or if they do, they're intended for something else, like the first three Aegis rituals.
Call to Slumber requires a few seconds to put the target to sleep-- where he might respond as well, and as a natural sleep, he could be awoken by a familiar, or grogs or a falling pot and still leaves him his magic resistance. If anything, I think the discussion demonstrates how the Parma facilitates magi gathering together. There is a lot of planning and effort here, on the chance a magus could get the Parma down and affect the other magus. Seven years of effort is no small investment. For an item with +32 Penetration, you've got a PeVi 26 item. If we did it as a charged item, you would need a PeVi lab total of 27, which is possible out of Gauntlet for the almost-specialist in the right environment (10Pe+5Vi+3Int+3MT+3aura+3S&M=27) as a season's effort but presumes a functional laboratory and only gives you one shot. Hopefully the target has both a Parma of no more than 4 and a Vim score of less than 12.
[Note, house-ruling the enchanted item Penetration modifier to a (+1Pen per +1Lvl) means this item is still possible right out of Gauntlet, but only affects magi with a Parma of 2 or less. To me, that's reasonable. YMMV.]
One point to consider, I think the discussion quietly ignores the efficacy of a muscular grog smashing the magus in the face with a brick. The Parma is not going to stop that, no matter how high it is and a grog just has to surprise the magus once. There are a lot more moments in a day where that's going to be feasible.
Callen don't speak about WoMS whch use the "general counterspell" guideline. he is speaking about "unravelling the fabric of parma" which use the specific guideline, and has no "half".
There is no general guideline for "unraveling the fabric of the parma." Review the guidelines on ArM5 page 160, nothing discusses Parma. The closest equivalent is the example given in Winds of Mundane Silence. You might infer a guideline by the "reduce a target's Might by the level of the spell + 10" option, but no one's suggesting the gradual erosion of the Parma. In the previous example, where someone asked "where the +10 comes from," those 10 levels come from the fact that the spell has a Voice range, adding 2 magnitudes.
Looking at this example, I'm confused:
I believe this is a guideline you've either invented or gotten from a book other than ArM5 and the three HoH books. If I'm mistaken, would you be so kind as to provide a page reference?
Step 2 appears arbitrary, perhaps incomplete. I believe you are establishing the guideline, but if so, why are you adding 4 magnitudes? Perhaps if you clearly stated the guideline for me, I would not be confused.
I see how you're arriving at your spell, and the steps are roughly what I would expect for calculating an effect, but the middle portion is unclear.
Now I can easily work back from WoMS to an Individual target, rather than a room, and calculate a relative guideline based on the effect, but reviewing WoMS, the exact text is:
"If this spell penetrates and its level + the stress die is double the Parma Magica x 5, then this spell dispels the Parma Magica."
So even the PeVi 10 WoMS isn't likely to affect a Parma greater than probably 3, possibly 4 on a very good roll. This spell really operates on different mechanics than most MR reducing spells by considering the whole level of the spell for the effect, and just has to be recognized for the difference.
I think the clarification on expiry that was in another thread made it rather less of an exploit?
IIRC, expiry was only valid to use with invested items.
What you're skipping over is the tail of that sentence-- "with a level less than the level +4 magnitudes of the Vim spell + a stress die (no botch)."
What's the level of the Parma Magica? As it's described, the Parma doesn't have a level because it's a ritual which provides a certain amount of magical resistance. It's analogous to a general ward against everything, but it's not a ward because it doesn't need to penetrate to be effective. That's the breakthrough nature of the Parma. Nowhere in the description does the text for Parma use the word "level."
Sure, the Parma is Hermetic magic, but like the Aegis, it's ... different. We have a spell which helps define how Hermetic magic interacts with the Parma with the description of WoMS, and so we can model spells after that effect, but I don't believe we can accurately establish a guideline from it because of its different nature.
Based on the spell description for Wind of Mundane Silence, I would infer the level of the Parma is (score x 5) for purposes of dispelling.
Parma isn't the only magical effect you'd need to do some inference on. Shapeshifting, Goetic Summoning or any other supernatural ability that gets caught by a dispelling effect that doesn't have an explicit example will also need some SG decisions. Personally I don't think the lack of an explicit example should make them immune to dispelling (or even necessarily harder) simply because they don't fit neatly into Hermetic theory. They would need their own Unravelling the Fabric of variant, though. The RAW strongly indicate that.
I think the prerequisite of a basis of knowledge regarding the effect covers part of that, but does nothing to explain how you would look at something like Shapeshifting, where the character is trying to hit an Ease Factor. As written, I think the guideline is looking at effects like the Infernal powers or Divine Powers, maybe Faerie effects, designed with a relative level. Fortunately, I went hunting and found the answer. Better than "strongly indicate," the rules tell us.
To handle Supernatural abilities, you've got to go to the section on creating Supernatural abilities in HoH:S, where on page 104 (bottom of the first column into the top of the middle column) it explains that in order to determine the level of a Supernatural ability for a PeVi (specifically WoMS!), you multiply the ability by 5 -- and there we have it.
This certainly confirms that the level of Cultellus is wrong, because the baseline for dispelling a supernatural ability is [based on these rules in HoH:S] ((Ability Score * 5) + 4 Magnitudes). Which means in order to dispel a Parma of 6 or less 50/day, Cultellus would need to be a Level 72 item (((Parma 6 * 5) +20)) + 16 (+32 Penetration) + 6 (50/day) ), rather than the Level 37 item it is. If the target had a Vim score of 2 or greater, it would not work.
And it would make an example of our unraveling spell look like this, presuming it aimed for a Parma of 3 or less with a Vim art of 5:
Unraveling the Fabric of the Parma Magica
PeVi 45
R: Voice, D: Mom, T: Ind
Destroys an individual's Parma Magica, so long as the individual's Parma Magica ability is less than 3.
(Base 35 ((3*5)+20) + 2 Voice)
It would need a casting total of 66, and the stress die roll would be unimportant. (Level 45 effect, +21 Penetration (21 Pen - 20 MR = Success!))
The equivalent WoMS, is: Winds of Mundane Silence
PeVi 25
R: Voice, D: Mom, T: Room
Cancel any magical effect with a level less than (25 + stress die)/2. Those with an active Parma Magica equal to or less than (25 + stress die)/10 [round down] lose their MR.
(Base 5 + 2 voice + 2 room)
This would need a casting total of 46, specifically with a stress die roll of 6 or greater. (level 25 effect, +21 Penetration (21 Pen - 20 MR = Success!))
Winds of Mundane Silence does not specifically differentiate between Realms, but one could surmise that it could-- requiring (allowing?) a version aligned to each. The WoMS needs less, but takes a risk that the stress die roll will be enough to destroy the Parma.
So, for one, you take a chance and might even hit a bigger Parma. For the other, there's no chance, and no benefit if you roll big.
Along with this, let us imagine you did penetrate the Parma and the magus had a Longevity Ritual with a score less than one-half spell's level-- it would be destroyed. Total side note: there's a real cruelty of a spell-- don't target the Parma, target the Longevity Ritual. You're certain to get his attention and send him into a panic as he scrambles to renew the ritual, which may require a pile of favors and depending on the season and his age, get him gone or cause him serious heartache. In a tribunal like Normandy, this would really, really suck.
"Dispel effects of a specific type with a level less than the level + 4 magnitudes of the Vim spell + a stress die (no botch)."
Ah! Ok, so we're both wrong--there's no "=" in there, but I see now how your base is correct. So that guideline needs about five extra words, I think, to read:
"Dispel effects of a Realm specific type with a level less than or equal to the base level + 4 magnitudes of the Vim spell + a stress die (no botch)."
(where I've bolded the words that need to be added. I guess you could leave out the "or equal to" and realize that if you roll the stress die (no botch) and get a 0, you're not dispelling your effect.)
Which means Cultellus is a fine item for a Parma of 5, so long as the magus has a lower Vim score. With the guideline as it is, Cultellus really destroys the Parma of magi with (Parma 5, Vim < 7) or ((Target's Parma<=5), Vim < (32-(Target's Parma 5))) because the item has no stress die roll to add to its effect.
*(At least, I'm pretty sure it doesn't get to roll a stress die-- does it? Would you allow the item to do so? I'm not sure I would...I don't know that I like the idea of items having a variable component to their effect like that. Sure, spell damage always gets a roll, because I figure people are in motion and could alter the outcome, or a magus casting could do it particularly well or poorly, but should an item in this instance? I've always considered item effects to be fairly static in that regard. Maybe roll once at the time of creation, or just make it an average of 5 for an item. If you wanted to get tricky, you could have a magus do a MT+Int vs an Ease Factor at the time of activation, and depending on what EF you hit, you get a specific "stress die" result for the item's usage. Now I'm conflicted.)
This does revise those spells from my earlier post to:
Unraveling the Fabric of the Parma Magica
PeVi 5
R: Voice, D: Mom, T: Ind
Destroys an individual's Parma Magica, so long as the individual's Parma Magica ability is less than 3.
(Base 3 + 2 Voice) {Base 3 + 4 Magnitudes->15, + stress die is greater than 15 which == Parma 3}
It would need a casting total of 26, still presuming a target's Vim art of 5, and the stress die roll would be unimportant. A little less than half of the time, you'd be able to get rid of a Parma of 4, but you'd need at least 5 more penetration on the casting total. (Level 5 effect, +21 Penetration (21 Pen - 20 MR = Success!)) A magus in an area with no aura, with a Stamina of +2, Perdo of 9, a Vim of 9, a Penetration of 1, using a Confidence point, a loud voice and expansive gestures could do it without spending a pawn of vis as long as he didn't botch. If he wanted to hedge his bet for a Parma of 4, he could either spend 3 pawns of vis or hope his casting roll was a 5 or better and then he'd need at least a 6 on the resulting stress die for the effect.
Yeah, I really want those 5 extra words in there, or at the very least the added word "base" for determining level affected by PeVi effect, just to avoid the confusion regarding using the base level of 3 (like you'd want to) rather than the casting level of 5-- because that would make it seem like you could hit a Parma of 5 with this spell, and you can't.
The equivalent WoMS, is: Winds of Mundane Silence
PeVi 25
R: Voice, D: Mom, T: Room
Cancel any magical effect with a level less than (25 + stress die)/2. Those with an active Parma Magica equal to or less than (25 + stress die)/10 [round down] lose their MR.
(Base 5 + 2 voice + 2 room)
This would need a casting total of 46, specifically with a stress die roll of 6 or greater. (level 25 effect, +21 Penetration (21 Pen - 20 MR = Success!)) But this could take out everyone's Parma of 3 or less in the room. There's really no chance of affecting anyone with a Parma over 3, because you'd need the stress die roll to be 15+.
Dang. That's some mental gymnastics over a short sentence.