An experiment in magic resistance.

Below are the house rules that my troupe and I have put together for magic resistance. They are offered here for two reasons: First, that it might be of interest to other players and those who enjoy the intellectual exercise of formulating rule systems; second, it may benefit from the scrutiny of a group of experienced (and in some cases, frankly, devious) players and storyguides who might find holes in it that we've missed.

It is not intended as any kind of 'challenge' to the AM5 canon rules - which I think are simple, consistent and entirely workable.

The design brief: The Parma magica should protect magi from magical attacks and give as little room as possible for exploitative spells that somehow bypass that protection.

However, the Parma should be a passive defence against magic - and the system should not allow spells that can be used make the Parma resist mundane attacks.

Further, there are some aspects to covenant life which I want to be persistently challenging. The original rationale was a 'survivalist' covenant - which entails that there are regular threats (magical and mundane) which are not easily warded, and must be physically (and magically) defended. This means there are certain magical things (some created objects or shapeshifted entities which are physically used to attack) that I would like Magi to remain vulnerable to.

House Rules for Magical Resistance

Any spell that automatically and directly affects the magus requires the effect to penetrate resistance.

There are some spells that do not affect the magus directly (e.g. creating a pit in the Earth). These environmental spells require a targeting roll to place them (e.g. above or below the Magus). The victim always gets a defence roll to deflect / dodge / avoid such indirect attacks.

A 'mundane' object can always penetrate Parma. If there is a spell effect upon a ‘mundane’ object, then the effect is suppressed unless it penetrates magical resistance.

Entities with a Might score - or that are created using momentary rituals - have physical attacks which count as 'mundane'.

A Magus can automatically overcome his Parma when he wants to physically interact with a magical object. Any spell effect that occurs as a result of his touch, must penetrate resistance to have any effect on him.

Creo spells:
Some magical creations count as 'mundane' for the purposes of magical resistance. Whether an object counts as 'mundane' is determined by the troupe when the spell is designed; judgements should follow these guidelines.

If Creo Animal or Corpus is used to enhance the characteristics of a 'mundane' object (within +5 of the average) - then the object still counts as 'mundane'. The troupe may decide similar enhancements for Herbam or Terram crafted items to also remain 'mundane'.

Animal: If the beast created is 'typical for its variety' then it counts as a 'mundane' object. A rule of thumb would be the bestiary - if the animal does not deviate from the normal limits for the creature's statistics, then it counts as 'mundane'. Note: animals are always created on the ground (or in water for fish) - only animals that can fly can be created in the air.
Corpus: A person created or enhanced by magic must be within normal limits of human statistics to qualify as 'mundane'.
Herbam and Terram: 'Mundane' versions of these objects will be found in weapon lists or are agreed (by the troupe) to exist in nature (e.g. a tree or a rock). These items are created upon the ground or in the hand. If they are physically picked up and wielded, then they count as 'mundane'.
Ignem, Aquam and Auram: Whilst these things exist in nature, magical versions of them are never considered 'mundane'.
(Note: with ignem it is possible to use magic to ignite something that is naturally flammable. Once lit, the flames are perfectly natural - therefore mundane)
Imaginem: Imaginem species are always considered 'mundane' - however spells that are placed upon a Magus need to penetrate Magical Resistance.
Mentem and Vim:
These effects have no mundane form and are always suppressed by magical resistance.

Intellego Spells: Always suppressed.

Muto Spells:
(note: this is definitely where the problem lies with suppressive parma - and I've suggested here a number of work-arounds to cope with potential exploits)

A spell effect may be expelled, suppressed, or leave the item 'mundane' depending on a troupe decision when the spell is designed; judgements should use the Creo definitions of 'mundane' and follow these guidelines.

The object is transformed to a 'mundane' one: The object is treated as ‘mundane’. (e.g. a boulder turned into a 'mundane' stone - strikes as a stone when thrown)
The object is transformed to one that is not 'mundane': The spell is suppressed. (e.g. a fire which has damage increased by +1 has the +1 effect suppressed - not the fire).
In cases where a harmful object is disguised as harmless: As the person brings their body close (within the Parma - assuming it resists) they sense the change momentarily - before the spell is suppressed – they automatically detect this change and have a choice about continuing their action. (e.g. the poison to milk spell - the magus automatically smells or sees the change in the liquid as it gets close to his mouth)
In the case where an object is shrunk and used as a missile: The force, therefore the damage, with which it impacts is equivalent to the object that was physically thrown. (e.g. with the boulder to 'unnatural' stone spell, the force with which it hits [and therefore the damage] is equivalent to the stone – see Rego and lack of momentum).
If a person consumes a 'mundane' object that has been transformed: The Parma Magica automatically expels the object as it reaches the end of its duration. e.g. a boulder turned into a stone is coughed up before the spell ends. The magus receives no penalty for an irresistable effect being expelled. (i.e. even if someone finds a way around previous rules then the object is simply removed, and no harm is caused)

Perdo Spells:
Always suppressed by Parma.

Rego spells:
If the spell effect upon the mundane object is one to make it move and strike a Magus then, assuming the spell effect is resisted, the damage associated with the object is negated. The object has no momentum and strikes with no force, because the Rego spell to move it has been suppressed. (note: this has ramifications for Strike of the Angered Branch type spells – the Rego requisite means they are resisted. However, Leap of Fire still works - because it is not the force or velocity of the fire that causes damage, but the proximity of the flames. Note though, that created fire is never 'mundane')

Now THIS is tasty, Badger. I can see adopting this, or something very similar, as a house rule for dealing with Parma. As always, you are a boon to the community.


your reasoning overall makes a lot of sense to me. You list many of those points that have come up as crucial over the last 8 or so years of discussing how to design the Parma rules.

Especially I agree with you that a Parma fitting the ArM setting would be rather suppressive (but unusable to dispel preexisting magic by moving against it) than blocking - but should not be abusable by either the protected nor an attacking magus.

This observation in particular always appeared crucial to me: a Parma that cannot be abused by an attacker would either be too powerful, or would need some intelligence to control it.
After all, game designer, player and character for a long time put a lot of brains into the design of spells within a complex and powerful system. After 17 plus years of tinkering we can safely say, that beating such designs with a dumb, simple and static Magic Resistance rule is impossible without overpowering Magic Resistance and introducing very weird side effects into the game.

Here the object, once back to its old size, would move under its weight, quite independently from the momentum with which it was thrown, and crush the target.

As you did above, I would here - as everywhere else where a Parma could resist - have the magus creating the Parma or the being protected by Magic Resistance decide what is resisted and what not, instead of giving intelligence under SG control to the Parma / Magic Resistance itself.
So I have to determine which information the Parma / Magic Resistance supplies to its creator / the protected being. IMO Technique/Form/Requisites and perhaps magnitude should be enough - though I know that then for carefully designed effects one cannot safely guess whether to better resist them or not.

Kind regards,


Thanks for the feedback so far :smiley:



It's this idea - that a (glowing multi-coloured, i.e. not considered mundane under the Creo rules) stone causes more damage when it strikes the Parma - that I want to nip in the bud.

If you conceptualise the Parma, not as a sphere or aura, but an infinitely thin boundary that follows the surface of the magus' body and clothing; then it doesn't make much sense (to me) for the damage to be that of a boulder.

To get around this issue I've simply ruled that an object, thus transformed, can only cause damage corresponding to the object that was thrown. So it shouldn't cause extra damage because of the large size of the object that was originally shrunk.


I have used this trick once - that's true - for the "harmful item disguised as a harmless one". However, generally speaking I wanted the magic resistance rules to follow guidelines that were reliable and consistent. My troupe is going to experiment with troupe play (myself as alpha SG) - with mainly experienced players, but one less experienced.

This set of rules is intended to put some control of magic resistance under troupe control (we rule whether a spell produces a 'mundane' object - or whether it is expelled or suppressed by parma). However, I wanted to avoid a Parma that was intelligent, or overly relied upon a magus' perceptions in deciding what was to be resisted. It seemed too easy for me to use (e.g. imaginem) spells to disguise spell effects, and trick magi into not letting their Parma resist.


we need to keep in mind, that we are talking houserules here, and have to do so in an abbreviated form unless we find time to write treatises instead of board posts.

Furthermore there are two kinds of houserules:
(1) kludges getting without any further explanation around real or perceived rules problems,
(2) concept changes providing also explanations of why the changed rule works as it does in the house rule.

Well, if a slingstone hitting my Parma at the height of my shoulder were transformed back to a 5 ton mundane boulder, I imagine that I would be killed by that 5 tons load appearing on my shoulder. And it is hard to just rule, without further explanation, that a completely mundane boulder in this specific case would just not weigh 5 tons.

Yes, you did.

So do I, of course. And I think that my suggestion is consistent - which of course doesn't mean that you need to follow it.

Magic Resistance under case by case troupe or storyguide control is what the FAQ ( describes as the big disadvantage of 'intelligent Parma' rules.
Just like you, I do not want to have a Parma with an own intelligence. But this is because I do not wish to have storyguide or troupe decisions about specific cases of Magic Resistance, which IME do not at all contribute to an enjoyable campaign.

If a magus setting up the Parma or a being protected by Magic Resistance can decide, that an effect which could be resisted is allowed to pass, they might be tricked into resisting a spell which they shouldn't, or vice versa. But in any case they - and not some troupe discussion - are responsible for the outcome.

How much or how little information you give out about effects which could be resisted by Parma would be yours to decide at campaign start. You could e. g. always give characters and NPCs the complete spell description of the effect.
I do not see how Imaginem spells can be used to alter that information, as no species are involved in it. In any case, a MuVi or PeVi spell hiding or altering the information would then need to penetrate the Parma because otherwise it would also be detected and - since determined to be a masking spell - suppressed, revealing the original properties of the masked spell.

IMO the skullduggery involved in having less information than this to base your decisions on is very mageworthy and highly desirable, though.

But we are talking houserules here, and if mine does not fit your or your troupe's style, you are of course at complete liberty to choose another.

Kind regards,



Aye ... fair enough :wink:

I really appreciate the feedback though - nothing like a good foil to help sharpen ideas :slight_smile:

Hmm ... I think there's a difference in conceptualisation here that might explain our difference of opinion. I don't imagine the Parma ever 'dispelling' the effects - merely suppressing spell effects that try to pass through the Parma boundary (which follows the surface of the skin and clothes).

When the stone hits (and remember a simple slingshot won't do, a 'mundane' object isn't affected by parma) - I imagine only the surface area of the stone in contact with the parma able to cause damage.

Whether that section of the stone is a stone or a small part of a boulder - the object does not have either the size or the mass to do more damage (the stone is not transformed back when it hits Parma).

All fair points ... hadn't considered the Vim spell having to penetrate Parma. Good point.

I have a great deal of sympathy for that view - 'magus' implies 'wise' after all, so making players have to think is no bad thing in my opinion :smiley:

The 'brevity' of Badger's patch makes me love Ars 5 all the more. While I understand the frustration some people may have with the cannon rule, I can't imagine stopping play to cross reference a sheet by Tech and From to see if I meet 'if- then' requirements of magic resistence. As the author it may seem intuitive, but I personally find the list to long. Good rules can typically defined in a simple sentence or two, such as the canon Parma Magica. :wink:

Touche, Tuura :wink:

I agree that this would be far too long and complex for a published rule set - however, the 'intuitive' rule is fairly simple.

Unless the troupe rule otherwise on a specific spell; any magical object that exists in nature is considered 'mundane' and penetrates Parma. Muto spells are not allowed to exploit Parma to cause more damage by the suppression of the spell.

Actually, I think you'll find that the Canon rules for Magical Resistance run to more than one or two sentences :wink: ... but I agree that in essence AM5 canon is very simple (far less complex than mine), consistent (whereas I've had to build in exclusions) and workable (as I think mine will be with my troupe).

I hope you read my first post at least!

I do like your rule though. Just tossing down thoughts. I could never use your rule with my long term group as I would have to change they way they think, but I could see a troupe of newbies picking up your ideas and having it make a lot of sense to them. People not biased by previous editions could think 'yeah, that's what magic resistance is suppose to be like!"

Well ... I'd argue that we're not newbies. I've been playing since the early nineties (AM2) and stuck with AM3 with a campaign that has been running for nearly 15 years.

In all the games I have run we've never made magi who shapeshifted roll penetration to bite a faerie - or required a magus who created a sword to roll penetration to hit a demon.

This 'patch' (though really it's an alternative system using a suppressive rather than blocking parma) is intended to keep our troupe 'logic' when it comes to MR rather than adopt the new rules. In riposte, I might argue that the AM5 canon is perfect for newbies (as they are simple and exploits will not be immediately apparent) :smiley:

Yes I see your point. In particular there is one player who lurks this page who would likely eagerly embrace your rule so he could keep things 'the way it was'.

(You know who you are!)

Isn't it the case with the standard Parma ,
that the "slingstone" just stops and slides harmlessly to the ground.
It would need a Rego effect included to balance it on your shoulder.

From my reading of this, that's not the canon rule, as the slingstone in Badger's case would still hit as a slingstone, not simply bounce off. Most of what I'd like to see is a Parma where there are few exploits, and those that remain would be difficult/tricky rather than simple.



With a 'blocking' parma (as AM5 canon) then any magical object is simply blocked (and slides harmlessly to the ground).

With a suppressive parma there is a potential exploit. As the shrunk object hits the Parma, the Muto effect is suppressed - which might suggest that the object strikes with its original size (e.g. a boulder, shrunk to a stone, strikes with the weight [and damage] of a boulder).

I'm arguing from a 'rule' perspective and with a (hopefully coherent) rationale that it doesn't.


You are correct. If a magus shrinks a boulder into a 'mundane' slingshot - and throws (or otherwise propels it) by mundane means - then it strikes as a slingshot.

Other than having a potentially unlimited supply of ammo - I don't see this as an exploit.

A boulder - turned into a type of stone that the troupe rules was utterly unnatural (e.g. a glowing, multicoloured stone) would have the transformation supressed when it struck the parma. I think it should still cause the same damage as the stone (rather than boulder) for the reasons given above.

I totally agree - I'm not bothered by level 35+ or ritual level exploits - but ones that are easy at level 5-15 are problematic (imo).

With the ArM5 standard 'blocking' Parma this is indeed the case. You might have noticed, though, that in this thread we are discussing how to improve a non-canonic 'suppressive' Parma far enough to make it work. And with that 'suppressive' Parma the effect turning a boulder to a slingstone would be suppressed - making it a boulder again.

Badger101's tricky idea for making this property non-exploitable is:
(1) The spell is only suppressed so far as it comes into contact with the Parma, which again is limited by the body and clothes of the protected being.
(2) What comes into contact with the Parma and is hence suppressed is just the surface of the slingstone, where there is no mass that can be increased back and crush the target.

If a suppressive Parma only affects the surface of magical effects which move into contact with the protected beings, it becomes however hard to explain how magically created fire, which does not need to get into contact with the Parma to ignite a being with (by Badger101's definition mundane) fire, can be resisted at all.

Kind regards,



That's a very interesting point (thanks again!) - but I still think it works by the definitions I have given.

The Parma suppresses magical effects that come into contact with the Maga. Therefore, as a magical flame strikes her skin, the (area affected by) heat and intensity of the fire is suppressed (therefore damage is negated).

If you look again - you will see that I've excluded (non-solid) forms from ever being 'mundane' when they are created. In the muto case (e.g. a fire has a MuIg effect to increase the damage) then the increased damage effect of the spell is supressed when it comes into contact with Parma (unless it penetrates, of course).

In 'philosophical' terms - I've made a separation between solids, liquids, gases and energy (e.g. heat). Solids can be classed as mundane (mainly because I don't want people putting their hands through them) - whereas more 'ephemeral' states of matter (which you can put your hand through) are not.

I think to have provided that already.

In short:

'Suppressive' Parma
(1) which does not resist or analyze already existing magical effects when moved into them,
(2) which tells the magus who created it a defined set of properties of every resistable magical effect which comes into contact with it without penetrating it,
(3) and which leaves the split second decision to resist such an effect or not to the magus.

Further elaboration is needed of:
(A) what is a magical effect that can be resisted - but here you can just take the definition of ArM5,
(B) exactly which properties of a magical effect become known - which is a matter of personal taste.

Kind regards,


The flames, however, would not need to strike the maga's skin to set her afire.

Maybe you were not completely precise when you wrote:

and thereby allowed effects from magical fire to be 'mundane' in your definition.

To work as you need it, AFAICS either your Parma would have to prevent flames not in contact with it to generate heat and secondary fires, or you would need to define matter (e. g. air) heated by a magical fire and secondary fires caused by that heated matter as magical and hence resisted by Parma, too.

Kind regards,