Would it be possible to create a spell that "destroyed all weapons in range of the Magi voice?" Something like:
PeTe(An) 30 (base 5, Voice +2, Group +2, An Requisite +1). This spell destroys everything the Magus perceives as a "weapon" within Voice range. Note: This spell only affects obvious weapons like swords or bows, not improvised weapons like chairs or vases. It also makes no distinction between weapons held by allies or enemies, so will not tend to make the Magus popular with his bodyguards.
The problem is the group target. Unless the weapons are neatly piled together they are unlikely to be a group. A group should be clearly defined. however, you could target the wielders of the weapins no problem, and as long as they are a group the weapons can count as such as well. Should be doable
The magus would have to perceive the weapons to effect them. So if he did not know the guy behind him had a weapon he would not effect it.
I would think it must be group. I do not think they would all need to be together in a pile but they must be close together. So a group of bandits or soldiers in a formation would work but all the weapons in a bar would not.
He would also need Herbam to effect wooden weapons. And animal to get some others ( bows made of Horn)
very few weapons are primarily horn or leather, so I think he can avoid the Animal requisite fairly OK. Then he will face a demon armed with a leather wip and find a worthy opponent, of course, but that is another issue :mrgreen:
I'm not sure trhat the spell itself could distinguish "weapons" from any other items of the same Form*. The caster could, but (as said above), any "group" has to be exactly that, a tight, discrete group. But if faced with a gang of armed thugs, it could be very flashy.
(* altho', perhaps, with a significant Intellego addition - but that would be at least 2 magnitudes, I'd think, +1 for the additional Art and +1 for being tricky.)
Thought - It might be more productive (given the Arts) to go for a ReMe spell that causes a "group" of humans to throw down their weapons - let them decide what is/not a weapon, and don't worry about it.
In terms of "targeting only weapons" - a ReAn "control squirrels" can be cast on an entire room of animals, and it will only affect the squirrels. As such, I don't see a problem with a PeTe "destroy weapons" effect cast on a pile of metal, and have it destroy only the weapons. In all likelihood, there's a Platonic Ideal thing going on that can identify what is and isn't designed as a weapon.
Philipus Niger in Guardians of the Forest has a spell that destroys weapons. Not sure of the exact stats, but it's a PeTe base and destroys a lot of weapons, not just a few. Look that up for a pretty much canon example.
I hear you, but for my money, I usually don't have much of an issue with that. Published is good enough unless it's a rather egregious mistake. Adventures are more prone to that IMO than source books, like a Tribunal book.
I don't mean that supplements should be thrown away because they are problematic. I own most of them, and not just so I can complain about them effectively online! I mean that it is extremely reasonable for a GM to put "what feels right to me" over "what a supplement says." Yes, every game suggests doing this, but it is very easy for an AM GM to expect to get a certain feel from his saga by following rules, yet this will often not happen.
To echo some of the other comments, this will destroy a "group" of weapons (rather than every weapon in Voice range). "The weapons in that armoury" could be a group, "the weapons carried by those men" could be a group too (assuming the men form a distinct group). Obviously, if there are too many weapons in the group (it is a very large armoury, for example) then it won't work, unless you use an appropriate size modifier.
Generally, I would be perfectly happy with a PeTe effect "to destroy weapons"; as KevinSchultz says, "control all squirrels" is fine. I also agree with Ovarwa that it shouldn't therefore target what "...the Magus perceives as a 'weapon'". It should instead target what "is a weapon".
The effect should destroy things like swords, but it is less clear what would happen if you cast it on an enraged mob of peasants who are attacking you with agricultural instruments (pitchforks, etc). That is something for your troupe to decide. I think that the simplest options to deal with in play are either to go for it only affecting things that are designed and made to be weapons (so would destroy a gladiator's trident, but not a pitch-fork), or go for it only affecting things that are being used as weapons (so would not destroy a sword in a scabbard, but would destroy anything deployed as a weapon in an on-going melee).
So, if my Magus were being attacked by a group of angry peasants wielding clubs and pitchforks, he could cast the spell I described above (with an He rather than An requisite, obv.) and it would destroy only the peasants' weapons, but leave the turbs' alone?
If you/your troupe decided that "a weapon" means "something used as a weapon", instead of "something designed as a weapon". And if you/your troupe decided that the circumstances were such that "mob of peasants" formed a sufficiently distinct group to "the turb". Then yes.
These seem like reasonable decisions to me; but only you/your troupe know for sure.
However, for what it is worth, I would say, that by the time the turb and mob of peasants were intermingled in melee, it would be too late to target the mob as a separate group. If you cast it while the mob of peasants is still charging towards the tower, then it would be reasonable to target them as a separate group.
Personally, I don't think you need to get too worked up about whether the judgement can be made consistently and objectively all the time. Something like "designed as a weapon" or "used as a weapon" is perfectly clear most of the time, and will probably be clear most of the time the spell is realistically going to be used in play. For dealing with cases where it isn't clear (which may not even come up in play, anyway), it is fine to just say "the storyguide fairly decides to the best of her ability".
I wouldn't throw an idea out just because it sometimes requires the storyguide to make a judgement about something. That's what she is for. The beauty/point/advantage of a tabletop RPG, over a computer moderated one, is that you have a storyguide and she can make judgements to cover unanticipated/tricky circumstances. If you can't trust your storyguide to try to make such judgements in a fair way, then adjudicating this spell will be the least of your problems...
Personally, I'd go with "designed as a weapon" for a pure PeTe effect (as identifying the platonic ideal seems to be an built-in ability to Hermetic magic), but "currently used as a weapon" as a PeTe(Me) effect that has to functionally read the minds of those using them to identify intent.
The question is here only, how the group targeted (ArM5 p. 113: "separated from any other things of the same type") is defined, and by whom.
I think, that most troupes allow a magus to affect "all those implements the peasants are wielding against me and my grogs" as a group target, without bothering much about the intentions of the peasants, and in which sense they wield them. The spell itself would need no knowledge of intent, or power of distinction between weapons and farm implements, at all.