Spell Deflection

What would be the guidelines for diverting a spell to another (valid) target?

ReVi, or MuVi like Mirror of Opposition [Form}?

There are ReVi tunneling spells (details in HP p.78ff), and MuVi spells changing the target of a spell just being cast (ArM5 p.159f, but make sure to read the errata on MuVi, too).


Thanks, I will dig up the errata.

Obviously the ReVi tunneling spells won't change the Penetration of the original spell, but I wonder about the MuVi.

A change of target is a significant change (ArM5 p.159 box Muto Vim Guidelines) of a spell, so the magnitude of the MuVi spell needs to be at the very least equal to the magnitude of the spell it attempts to retarget.

Whose spell does your magus wish to deflect with MuVi? Is the deflection coordinated with the original spell's caster?
If we assume an uncoordinated MuVi, it needs to be fast cast, and its Penetration needs to beat the original spell's one - so the MuVi caster better be superior.

The target of the MuVi spell is the other spell: if the MuVi spell just retargets it, in general it shouldn't affect its Penetration, too.


It is for our Vim specialist, who is moving their character concept towards 'witch hunter'.
Doesn't have significant offensive magic, so thought it would be a smart idea to use a hostile wizards spells against them, rather than blocking/counter-spelling it, then casting an offensive spell.

We were prepared for fast-casting. I had totally missed the bit about needing to beat the spell's penetration. So, I think, has everybody else in the troupe.
I will have to re-read the Muto Vim guidelines again.

I was thinking. Is there anything that can boost penetration in this case? An arcane connection to a spellcaster is also an arcane connection to one of his/her spells?

Edit: I mean to bost the penetration of the MuVi spell, in order for this to have effect.

MuVi magic is cast on spells themselves in the process of being cast. So you can refine the question to: is the AC to a magus also an AC to the spell he is currently casting? This could be answered 'yes' by your troupe without opening a can of worms.

MuVi spells to be fast cast in an adversarial situation better be Formulaic spells mastered for fast casting. So the ArM5 p.44 Virtue Life Boost might help their caster a lot, not only but also with Penetration.

As a word of warning: specializing to combat other Hermetic magi rarely pays off for player character magi. Best review the likely situations where the Vim magus really needs to deflect a hostile magus' spells, before putting significant resources into handling this.


EDIT: Life Boost is generally very useful for versatile magi inclined to study and resolve complex situations with magic. Most Vim magi belong to this group.

Spell Mastery will help with the Penetration of the MuVi spell.

The Penetration Mastery adds Mastery Score to Penetration - it is already added to Casting Score so in effect Mastery adds twice. However this is a small number, it is most effective when there is a Penetration Modifier (AC, sympathetic magic etc() but I doubt this situation will have this.

Indirectly the Rebuttal Mastery helps. Rebuttel adds Masteryx3 to the effective level of the spell, so the effective spell levels needed to affect other spells is lower - leaving a larger amount of the Casting Total for Penetration.

Also, a Talisman with the right S&M attunement helps with Casting Total. Hornbeam's "+6 Vim on hostile magic" seems useful.

But remember that Fast-Cast spells are -10 to cast, and this severely hampers the Penetration. And they need to be sufficiently fast, so to pull this off the spells used all need both Fast-Cast and Quick Casting Materies, and you'd like the Fast Caster virtue.

Also consider personal perdo Vim wards, with a +1 "does not negatively affect my magic" magnitude modifier.

(Named or restricted wards are a thing - Aegis of the Hearth being the most well-known. However, it's never listed how much of a modifier it is. The closest I know of are the Columbae, who get to add named restrictions to circle/ring wards for free. Using the standard "reasonable modifiers can be added in with little difficulty" rule, I'd argue it's a +1 for everyone else. I'd make the same magnitude if you wanted a ReAn ward to "not affect sheep" or "only affect sheep", for example. Of course, since it's not listed anywhere, you'll need to run it by your group and GM first before you use it. YSMV.)

If by "witch hunter" you mean hunting non-Hermetic magi as opposed to someone specialized in wizards' wars or hunting renounced magi, this MuVi solution has a severe problem:

Yes, I just noticed this as well, and I'm still puzzled.
Considering what you can with Rego or Perdo Vim it makes no sense that Muto can't as well. Especially considering the Ex Mic. tradition of "Line of Pralix" and Rebuttal Mastery

Overall Vim magic used to affect other magics have guidelines in two types:

  • Universal guidelines, which will affect anything but is hard (like Winds of Mundane Silence)
  • Specific guidelines, which require a specific tradition (e.g. Hermetic or Gruagach) as well as type (e.g. Terram or Cursing) to be specified, but thay are much easier than the universal ones (like Unravelling the Fabric of [form])

Until now I had not noticed or even suspected that Muto Vim could not also do this. For me it seems an error, and I'd like to ignore that single sentence, and take a cue fro Rego or Perdo guidelines.

Such a spell would be like:

Strike the face in the Mirror
MuVi 30
Spell causes another spell being cast to hit another valid target, even the caster. This spell needs to be fast-cast in order to get the timing right, and needs to have Penetration exceeding the target spell. Guideline used is "superficially change a spell cast by another of level+1 magnitude of them Vim spell". In the design 2 magnitudes are used to get R:Voice, which means this spell can affect spells up to level-1 magnitude. Thus, the level 30 spell can deflect spells up to level 25 back a the caster or another valid target. For magical effects not based on spells use Abilityx5 for effective level.
(Base: Gen, +2 Voice)

Imagine this spell backed up by 6 levels of Mastery (for Fast Cast, Quick Casting, Rebuttal, Penetration +2 more) to affect spells or effects cast up to level (25+3x6=)43.
Sure getting Mastery 6 is a lot of work, but considering it can be the swiss-army knife of the witch hunter it may be worth the effort.
It also requires good casting speed ( meaning Qik and Finesse) as well as good Arts and helpful virtues to pull off.

Thanks for these two suggestions. They seem in fact the way to go with deflecting spells. I don't see any other way of doing it.

(Edit: Sorry, I didn't see the previous post, but the posterior question remains

So the spell to deflect will look like this:

Deflecting the Pillum of Vim
MuVi Gen. R: Voice D: Mom T: Ind
This spell allows the magus to alter the target of a spell as another spellcaster is casting it (so you need to fast-cast it or coordinate with the other caster). The deflected spell takes full effect in the target designated by the caster, that must be in the range of this Mu Vi spell.The deflected spell must be at least one magnitude lower than this one.)

But you would need longer durations in order to affect longer duration spells. What happens if you target a sun duration spell with a diameter duration deflection? The spell is deflected for two minutes and then resumes its effect in the original target?

The latest Muto VIm errata says the MuVi spell needs to last only as long as the casting of the target spell, not its entire duration. This is primarily a point (also made in Through the Aegis) for Wizard's Communion used on Aegis of the Hearth. As Aegis is a Ritual it takes a Duration more than Momentary, or even Diameter, to cast - hence the Communion needs to last longer as well.

But as for deflecting spells, they only need to last a moment, while the target spell is being cast. Once the spell has been diverted to another target it continues to affect said target for as long as it may last.

Ah, makes much more sense that way, yes.

Once again, I regret not reading the Muto Vim guidelines close enough. Though I was originally thinking this sort of spell would be under the description of ReVi.
Also, there was a thought that the writeup on Unravelling the Fabric of [Form], which inludes the line

indicated that it was possible to create other Vim spells that targeted non-Hermetic Magic.

Though if this was for Wizard War, imagine the efect of reducing the enemy's spell range to Personal.

In any case, the concerns that One Shot expressed previously ("As a word of warning: specializing to combat other Hermetic magi rarely pays off for player character magi. Best review the likely situations where the Vim magus really needs to deflect a hostile magus' spells, before putting significant resources into handling this.") are more than justified.

I don't know how trigger happy is your saga, but if I were you I would probably be thinking in ways of making my overspecialized magus (you will need specialization to pull-off that thing) useful in normal adventures. It seems not impossible, as a good vim could be exploited with various Perdo Vim spells to destroy magical/faerie/diabolical/creatures..., circles of protection, mystical identifications of various types, collaborative casting with other (more) useful magi...

The line

was always in ArM5, both in 1st and 2nd 'Printing', and never was errataed. I also never doubted its necessity.

MuVi spells do intricately interfer with magic being worked by others: they do not just extend, tunnel, block, ward off or delete it, but either cooperate or barge in on it. To do so, you need to have the proper tools, and the proper understanding of the others' operations. Both are limited to Hermetic Magic here.
This means for example, that - no matter how powerful an Hermetic MuVi magus you are - you cannot cast a MuVi spell on a Bjornaer changing into heartbeast form and thereby modify the beast she turns into. If you are a Bjornaer yourself, you might understand, why Hermetic magic just cannot do this. Otherwise you barge in on magic you do not understand, and your MuVi spell just doesn't take hold on it.

There is a problem with the (ArM5 p.159f) section on MuVi: it was written extremely concisely, and then errataed twice. This was likely done to limit space for a single Form-Technique combination. Every phrase in its guideline and spells had to carry a lot of weight from the beginning. When the text later was found insufficient in several aspects, the errata didn't make it any more readable.
So I advise newbie players to just skip MuVi, and still don't know whether the effort to understand and integrate it with a saga is worth its benefits. But house-ruling parts of it whenever they come up in your saga is really asking for trouble "with a firm voice and bold gestures".


Perdo Vim and Rego Vim also work on spontaneous magic, but Muto Vim doesn't. Sure, that's for game balance. But the idea of more intimate understanding of the magic and the careful control necessary match pretty well between not spontaneous and not non-Hermetic. You can always house rule that away if you want, though.

What about the Parma Repercussa fold from HoH:TL, page 32 instead of MuVi?

Indeed. Although it is important to also note that MuVi itself can be sponted. In fact, that's one of the possible builds of a MuVi magi - one who is has a 25 or 50 casting total in MuVi, and then just/5 sponts all of their MuVi effects on the relevant lvl 5 or lvl 10 formulaic spells. The reason for this being that most MuVi effects need to be highly specific, to the point that they're rarely all that useful to spend the time to memorize. However, if you can SPONT all of your MuVi effects, it becomes a much more viable build.

Combine this with 2 low-level enchanted items that grant a lvl 5 Mystic Tunnel and a lvl 5 Maintain the Demanding spell, and it's relatively easy to get your lvl 5 effect up to an equivalent of lvl 30.

Of course, you'll need to consistently be able to Concentrate at a 9+; so, probably Cautious and Pussiant concentration would be useful. (Or just spent the xp on it.);and you'll need to clarify with your GM just precicely WHEN the MuVi spell is cast. (is it during the same round as the affected spell, or is it cast the round before? Do you need to fast-cast one or the other? My interpretation is that it's cast the same round without an additional penalty, but YSMV.)