I was reading the first chapters of Hedge Magic earlier today, and came across the discussion of Elemental summoning.
That made a thought cross my mind, which sent me to my copy of RoP: Magic to look at Magic Spirits and Magic Things chapters. That sent me back to My Core book to look at the discussions of might-y creatures there.
I was left a question about the nature of vis. I will approach it by way of analogy.
Desade ex Flambeau, bored by his brethren's tendency for immolation and direction destruction, has decided he wants to find a new, different way to inflict pain and agony upon others. He decides upon trying to find a way to use his ReCo abilities. Base 10 transports a target up to 5 paces. So Desade designs:
Limb from Limb
R: Voice, D: Mom, T: Part
Teleports the right arm of the target to a spot in front of the magus or 5 paces closer to the magus, whichever is shorter.
(Base 10, +2 Voice, +1 Part)
As far as I can tell, there is nothing that breaks the Limits of magic about this spell. Comparing it to Parching Wind (Core p. 123), it has similar level... one could imagine that a ReAq(Co) spell of base 10 could rip the water out of a person, rather than simply making the water disappear. In fact, with maybe a magnitude up, I don't see any reason this liquid couldn't be blood, rather than water (we already have the corpus requisite, after all). There's also The Promenade of Caesar (Ancient Magic, p. 56, and some discussion of standard Hermetic magic's abilities to target babies as Target:Part on the preceeding page), which suggests that ReCo can be used to teleport an unborn child out of its mother.
(Part of the preceeding page I refer to does note that prior to the second trimester, Hermetic magic cannot target an unborn child, even at T: Part, which is interesting, as it's rationale for why it only works after the first trimester is that it's a flaw of Hermetic Theory, but notes its the inability to distinguish child from mother which is the problem.)
So, what's all this got to do with vis, you ask?
Well, one day, Desade ex Flambeau gets bitten by a magic wolf, and, after healing up, Desade decides that magical creatures need some abuse, too. Feeling imaginative, and having had such success with using T:Part on humans, Desade decides to learn some Vim, and soon pops out another new spell.
One's Pain is Another's Gain
R: Voice, D: Mom, T:Part
Teleports the vis within the target into the object held in the caster's hand.
(Base 10, +2 Voice, +1 Part)
Obviously, this spell would need to penetrate. But, given all the discussion in Ward conversations about how easy it is for ReVi specialists to generate high penetration totals at level 25, that doesn't seem like it'd be a big hurdle.
The obvious first argument against such a spell is that the RAW treats severing a limb as PeCo20, so a ReCo spell should be at least as expensive. On the other hand, it's pretty easy to make a 5-pace teleport of a whole body deadly by the integration of all sorts of physical features, from fires to steep drops to a well-braced spear. (The question of what happens when you try to teleport one thing into space taken up by other stuff is one I don't think the RAW has addressed, but you can always teleport something right above the item of interest.)
But let's assume I cave to this first argument, and say that ripping parts off people is Level 20 base, rather than Level 10. That ups the numbers, but still leaves me with my vis-analogy.
The next argument I can imagine is that one has to be able to sense the target of the spell, and that if one is targeting a part, they have to be able to sense the part. I'd say Twist of the Tongue (Core, p. 133) contradicts that: it affects the tongue, and gives no indication that the tongue must be seen to be affected. (Unless you imagine the spell is only used in very specific circumstances.) I'd also note that R: Touch works even for a blind magus, and, additionally, that I could design a R: Touch, T: Room version of the spell that makes the arms fall off of everyone in the room, even if I were blind.
But, even if we assume that's true, let's say Desade has a ring of vis-sight. That has to penetrate, too, but is there any reason such a device wouldn't see the vis inside a creature if it had enough penetration? Especially since most creatures have the vis already concentrated in a specific part of the body? The notion that I could not see the vis while the creature was it was dying, and the vis would suddenly become visible once the creature was officially dead... well, I'd need someone to give a good argument for why that makes sense. (It seems like vis-sight is one handy way to detect spirits, since vis is easy to spot, and, therefore, can have high penetration totals.)
The final argument I can imagine is that any act which causes damage is Perdo, not Rego. There's soe implication of that in the rules; there isn't a reAq version of the PeAq spell that dehydrates things/people. On the other hand, one can Muto things into damaging versions. One can create damaging versions of things. Admittedly, those are indirect damage.
So, assuming I buy that final argument... the rules normally say that DEO and its ilk destroy vim proportionally to their destruction of the target's might. Does it at least seem fair that a Re requisite on such a PeVi spell would remove the vis in a usable way, rather than destroying it? (By analogy, a Re requisite on the PeCo sever-a-limb spell seems like it ought to allow the severed limb to be teleported as part of the severing.)
So what do you the rest of y'all think? Would a ReVi effect to remove vis from a live being work? Would a PeVi(Re) effect to remove vis from a live being work? Could one ReCo a limb off rather than PeCo it? If so, what would the level be? Should ReCo a person 5 paces over an upturned spear be more deadly than a PeCo spell?