Can you use T:Part with Vim effects that affect spells? And what is exactly a "part" of a spell - is it the full spell on a Part of its Target? Is it instead Part of the spell's functionality?
This question came up when discussing revisions/clarifications of the Aegis. Particularly under some revisions, the Aegis becomes a significant barrier to entry, so waging a wizard war becomes practical only from outside, or after having removed/dispelled the Aegis. Dispelling it is not too hard (all proposed revisions/clarifications treat incoming spells exactly as currently written), but it might incur charges of deprivation of magical power by wizards not involved in the war at the covenant of the defender. However, no such charges could be reasonably brought up if the attacker dispelled only the portion of the Aegis "in" the sanctum of the defender (which the attacker can lawfully raid).
So, for example, using a dispel with Target: Room to dispel Aegis effects from just one room of the covenant?
To me, that makes logical sense to be possible. Of course, the casting of the Room dispel would still have to get past the resistance of the rest of the Aegis if cast within it. Right?
I have to say I was fascinated when you brought up the idea of a Perdo Vim spell with target Part to destroy only Part of an Aegis, and I must say I like the idea. I can't find any reason why it can't work. And it gives me a whole bunch of ideas with Perdo Vim. For example, using target part on a Disenchant spell to remove an effect use restriction on a dead magi's talisman.
I had had similar plans before. But in my case I was thinking of ReVi to suppress a portion of an Aegis using Part. That way I wouldn't permanently wreck it.
Almost. The end result would be exactly that, dispel the Aegis in a single room.
I think the mechanics would be different: the effect should be (I'd say) T:Part, rather than T:Room. T:Room would dispel all spells "located" (completely? partially? I guess completely) within a particular Room. Instead, you want to dispel T:Part (e.g. something as large as a room, small r) of a single spell.
Or, as callen is suggesting, suppress it, but that's way, way harder.
A ReVi spell with Part could be used to suppress or sustain part of a spell's target's- such as a single member of a group affected by a spell.
I, personally, would also allow a Perdo requisite to make a Rego Vim spell that suppresses part of the spell's power to weaken (but not dispel) an ongoing spell, such as one that reduces the range of the spell. This would typically be an effect with a duration, so reducing the duration of the spell would only really apply for as long as the duration lasts (which may not be relevant).
Actually, I have a ... queasy feeling about both ideas (destroying/suppressing a Part "location-wise" or "function-wise" while allowing the rest to operate as normal). The fundamental issue is ... can a T:Boundary spell still remain a T:Boundary spell even with a hole in the middle? Can an enchantment still keep working if you destroy an effect restriction? Or would it just all hopelessly unravel? Note that the two questions above may well have different answers.
On the one hand, in a person you can't just kill the heart, and leave everything else operating as normal: if you remove an effect restriction from an enchantment, it's still a "valid" enchantment, but if you dispel a room within a T:Boundary spell, it's not quite a T:Boundary spell (I mean, the room could not have been excluded at casting time).
One interesting consequence of this is that maybe it makes the Boundary result "unnatural", so as soon as the dispelling magic stops being sustained, the dispelling is cancelled and the Boundary reforms? This would effectively work as suppression!
On the other hand, while removing a room from a Boundary is probably like removing the heart of a person, I am less certain about removing a restriction from an enchantment: is it removing a Part like the heart, or is it removing a property of the whole like weight or solidity? Note that the latter, with PeCo, uses a different Target and a completely different guideline, much higher.
I usually form quickly strong opinions, but on this I feel I am on deeply uncharted terrain (there's notthing like this in published material, right?) and there are certainly issues of game balance, consistency, and aesthetics that are escaping me at the moment.
I phrased my question incorrectly but your reply confirms what I meant to ask. And yes, it still seems logical to me. It should be possible, given the existence of Target: Part.
It's two or three weeks to our next session, but I'll try to remember to run this past my troupe and see what they say.
I don't believe there's a canonical Perdo Vim that uses target Part, no, but bear in mind that most of what's published are general spells, The lack of such spells doesn't mean they can't be designed, so long as they make sense.
While there is nothing preventing using T: Part with Perdo Vim, I do not think a ritual or enchantment would survive it. They are not like a solid object in which if you destroy part of it, the rest remains. They are a complex web of fluid vis bound by the magic of the caster/enchanter. Destroying part of that web means that the the structure containing the fluid vis is compromised.
While if you can or can not is completely YSMV, personally I am on the side of pure PeVi causing unraveling. If someone wished to allow this in their game, I would recommend doing something like adding a Rego Requisite to "tie off" the remainder of enchantment/ritual so that it does not unravel.
Effect restrictions are more complex, since it is possible to have one as a completely separate enchantment of an enchanted item. Destroying one like this would be removing a single enchantment from a device with many, so should not damage the others. You could view them as installing a lock into the enchantment, which is unlocked by the nature of the person using it. How tightly integrated that lock is to the rest of the enchantment then becomes the subject. If it is some little part tagged on then cutting it out is not very damaging. If it is something that the entire rest of the enchantment is built around then cutting it out rips apart the enchantment.