Enchanted Devices and negative Penetration

The recent Aegis threads seemed to hang up on whether or not enchanted devices can work with negative penetration.

Typically you build an enchanted device in a high Magic Aura.
Hypothetically you build the enchanted device MacGuffin in an Magic Aura 7, and it generates an effect with zero Penetration while in the Magic Aura 7.

Will the enchanted device work against targets with no MR or other supernatural resistance, in the following situations:

  1. Magic Aura 5 - should have a negative 2 Penetration.
  2. Mundane, no Aura - should have negative 7 Penetration.
  3. out-skirts of Faerie Forest, say Faerie Aura 2 - should be -7 + 1/2 * (+2) = -6 Penetration
  4. Typical town, Divine Aura 3 - should have -7 - 3 * (3) = -16 Penetration.
  5. near the consecrated alter of an important cathedral, say Divine Aura 8 - should have -7 - 3 * (8) = -31 Penetration.

Once we have this baseline, questions about Aegis of the Hearth will have more context.

devices dont add/subtract modifiers from the aura that they are in to their penetration.

A device with no penetration in a magic aura 7 will have no penetration in any other aura too.

The advantage to making MacGuffin in a magic aura +7 is that you get to add +7 to your lab total which gives you 7 more lab-total points to add to penetration (or other things). If memory serves me it is explicitly listed as one of the primary advantage of magic items in Ars magica that they are not affected by auras.

EDIT: Normally magic items cannot fail to cast the spells that they have been enchanted to cast either. There is no roll involved in activating an enchanted item once activated it casts its spell and that it.

I don't think you CAN build a magical device to have zero penetration in Magic Aura 7. It'd have a penetration of 7 in the Aura 7.

But then you are adding aura twice, one in lab total that you can spend in penetration or not, and another when casting.

Unless we go back to the OP scenario of having negative penetration. To which I'd say no, mostly because the idea of having to keep track of all auras were items were enchanted sounds like a hell of extra administrative work.

You have a +7 to your lab total. You can use it to get a +7 penetration (actually +14 per the RAW) for the item, more uses per day or whatever. Once the item is finished, it has its own penetration total.

the aura modifes the fixed penetrration total of the item. So a +3 magic aura will add +3 to the listed penetration of the magic item, and a Divine aura 2 will reduce it by -6.

Magic resistance is also affected in the same terms.

In your example to have a Penetration 7 in a magic aura 7 your items is simply a item with 0 penetration in its build. If it goes to a no aura zone it will have 0 penetration, and it will have a penetration total of -6 in a divine aura of 2.

Per the RAW a 0 penetration item in a 10 divine aura will have -30 penetration, but will still work. Nowhere it says anything to the contrary. Since it is not a HERMETIC CASTING total (the one that fails in the casting total does not reach level -10) it should work. However, I find that debatable so I would make it fail if the difference is so large.

Funny enough my table troupe has never used modified penetration for items in auras. An overlook going back more than 25 years now.

Yes. And as far as I can tell, that RAW.

But device Penetration is fixed when it is enchanted, it is not affected by the Aura it is in while used. Only spellcasting, mystical abilities, and creature powers (ArM5 p 183). Devices aren't mentioned. Not any place I can find, not in the Lab chapter either.

Auras may modify MR however.

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Byt you're not.
If you add Aura to Lab total in order to get higher Penetration, then it's a device with fixed Penetration. You won't be casting a spell, but just activating an effect.

If you add aura during casting, its not a device but a spell, and therefore has not been factored in already.

And in both cases, if the target has MR, and is attuned to the seame realm as you, he adds the Aura to MR.

Where does this come from? Aura is not mentioned in any of the MR formulæ in the formula review in Core.

Core rulebook, Realms chapter, page 183 insert box. There is an entry called "Magic Resistance".

Even for Hermetic magus on magus fight it is important to remember. If the attacking magus has so much penalty, that his spell does not actuallu go off, then it doesn't matter if his victim's low PM means he had negative MR.
Also, a magus blasting away at a faerie inside a faerie aura, the magus only daas ½ Aura to spellcasting but the fae adds full Aura to MR

I'll admit, that I suddenly recalled once believing thet device Penetration was modified by Aura. I had forgotten, and now I can't recall why.

But look at Through the Aegis page 151, right column, device 'Clasp of the AMbassador' effect 'Aura of Equality'. It has Penetration 32 and is noted to ensure it would work on an archbishop with Commanding Aura while inside a cathedral (Dominion 5).
Commanding Aura for an archbishop is MR 10, then add 5 for the Aura. Penetration 16 would have sufficed. Bu I do believe I at the time was sure the Penetration suffered a -(3x5) modifier.
Now, I don't see why. Not any source I can think of or find. Anyway, adding +16 modifier to the design, already including +4 for uses/day, made the device a round level 40, so who cares?

Thanks Christian.
I trusted the formulæ listed to be complete. Obviously a bad idea.

It seems that whether aura is added to penetration for items is left open to interpretation. Items are not mentioned, but the aura rules seem to be stated as generics, with the special cases being added as examples.

One can make a case to say that items should be the same as creatures. No roll so aura modifies penetration directly. The fact that aura was used in the lab total in creation probably applies to magical creatures too, who likely have drawn some of their power from the aura where they were born or where they reside, power which may boost their penetration.

realm interaction chart insert, page 183 core book:

Penetration: For magi and characters with mystical abilities, the aura modifies the roll to use the ability, which means that Penetration is modified. The aura modifier does not apply to Penetration twice. Thus, a magus in a Divine aura of 2 takes a –6 penalty to his Casting Score. This automatically educes his Penetration, as that is calculated by subtracting the spell level from the Casting Score. The aura modifier is not subtracted again from the Penetration total. For mystical creatures, there is no roll to use the ability (see page 191), so the aura modifies Penetration directly.

The "so" in this sentence for me means that items are also affected since there is no roll there either.

Does the explanation of Invoke the Spirit of (Spell) in the Theurgical Section of TMRE provide any insight?

I interpreted it as Xavi did, the same 'item affected by aura', but yeah, it's not explicitly stated that mystical items are modified for penetration. It's a logical extrapolation, but it never was stated RAW.

I think that interpretation has very weak arguments. The word ‘device’ is mentioned nowhere, and you grasp that meaning out of the end of a sentence ruling about creature Powers.
Also, the Penetration if devices is defined in the Lab chapter under ‘using devices’ p100 as being 0 “unless an effect modification has been made”.
Plus, the definition under Aegis of the Hearth is that foreign devices are “resisted” which is defined for spells as “Penetration less than level of Aegis means it fizzles”. Nowhere is Penetration of a device ever modified by anything. It is only defined by the levels added for that modification during enchantment.
The very essence of a device is that it trades vis cost for an effect which always works regardless of circumstances normally affecting casting totals for spells. Aura neither helps or hampers Penetration.

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I’m not sure.
Reading the example, Gunnar’s spirits activate their creature (well, spirit) powers which are affected by Aura . Oddly enough the spirits seem to be generating casting totals - I thought powers just always worked, and only Penetration needed to be calculated. Anyway the Penetration total is affected by Aura, which ArM5 chapter Realms clearly states.

However earlier in the description of the spell Invoke the Spirit of it says “Penetration for the spirit is determined like an enchanted device effect”. But the following explanation says only “ base zero (Might-spell level, which is not like normal for powers, as this is Might - magnitude of power)” but also adds +2 per extra level - same as for devices.

Aura is not mentioned in the rules breakdown. But a fair extrapolation for the example does use Aura modifier.
However the core rules IMHO does nit support it in any way.

We extrapolate from a sentence that references a usage of a thing that does not require a roll. It happens to be a creature power. You interpret it restrictively. We interpret it as one case where rolling was not used.

I think it is fair to say the issue of whether devices penetration is affected by aura is a house ruling, but if it is affected, the issue is secondary when regarding Aegis of the Hearth, since it already has an explicit rule.

In Legends of Hermes, the rules do state quite unequivocally that Penetration of items is affected by realm interactions. See LoH True Understanding of the Realms virtue which starts on p15 but the specific mention of items starts at the last line of the first column on p16.