Have to say I love this game but it does seem to have more unanswered (or unanswerable) questions than most.
Do enchanted items have any inherent resistance to magic? Can they easily be transformed with muto or destroyed with perdo? Muto has less logic issues as it would endure only as long as the spell lasts, but perdo seems quite final. I realise the hermetic limit of essential nature exists but totally confused as to how this applies to perdo.
Also, there seems to be no roll to activate an item's powers, therefore by extension they function reliably even in a powerful divine aura, and incur no chance of botch, which seems odd.
On another note, I am about to run a Tribunal gathering, with trade of enchanted items being promoted by Verditius displays (as mentioned in the article in Sub Rosa 5). However I would be glad of advice/opinions concerning a reasonable trade for items that do not cost Vis to create, such as Casting Tablets (Covenants) and charged items. In Mystery Cults it is suggested that these would cost what a Magus could extract in Vis during a season, although if I'm not mistaken that means that a low power item costs the same as one of much greater power.
In general, no.
But keep in mind that e.g. the parma of a magus extends "a little" beyond his body, so the enchanted ring he is wearing is protected.
Though not the enchanted sword he is wiggling, unless it's his talisman etc. etc.
In general, yes.
Definitely, at least in the vast majority of cases, if used to simply "destroy". Also, note that if you change (through Muto) something into something else that is exceedingly fragile, and it gets destroyed (perhaps even by the environment) it stays destroyed once the Muto effect ends.
Heh. The simple rule is: if you can destroy/hamper/cripple something so that the end result is "natural", then D:Inst Perdo can effect the change, and the change will remain after magic has run its (brief) course. Since most things and beings inherently have the potential of being crippled/dead etc. as part of their essential nature ... Perdo just works very well in practice. There are some changes that can be effected by Perdo (e.g. destroying a person's weight, making him weightless; or destroying his ability to emit species, making him invisible) that make the end result "unnatural". These changes remain only as long as the magic persists, and disappear as soon as the magic has run its course.
Indeed... though of course within a powerful divine aura (the user of) a magic item might have other issues to contend with.
I was also wondering if items can have a deactivation trigger built into them as part of the basic enchanting process. Obviously the situation where something stops functioning when no longer worn is one option but say you have a carpet that has a muto effect so it can be made rigid to allow flight, how do you then after landing cancel the effect without having to wait for the duration to expire? Is there an example of this in RAW anywhere?
Concentration duration and then setting the item to maintain concentration is the usual approach to this - page 99 of the main Rules has an example of an invisibility ring that only works whilst on your finger.
Does anyone use a house rule that alters this state of affairs whereby enchanted items are exceedingly fragile? I suppose one idea could be that the highest effect level in an item would be its effective magic resistance against any spell attempting to affect it. Alternately what do you think about an item having an essential nature as a result of it being magical that means that perdo magic can only temporarily destroy it. It just seems to me far to easy to destroy things in the game. So imagine the mighty Excalibur being wielded by someone with no magic resistance. A cruel sorceress casts a perdo terram at voice range (total level 15 [base 3 +2 metal, +2 voice] achievable to not especially powerful magi even as spontaneous magic) which utterly destroys the sword. Any opinions?
On another note thank you Salutor for your response. However I'm aware of the item concentration scenario as I alluded to it in my post. What I asked was if anyone is aware of the mechanism for how spells/effects can be ended prematurely. Certain spells in the main book are designed this way with props (for example MuCo Cloak of Mist). How can a cancelling trigger be built into an item/spell and does this have any design cost?
An only somewhat tricky way to give am enchanted device Magic Resistance independent of its wielder is, to bind a spirit into it with the TMRE p.27 Minor Hermetic Virtue Spell Binding. As long as the spirit inhabits the entire item, its Magic Resistance by ArM5 p.85 The Function of Magic Resistance also covers and protects the entire item.
Discuss this with your troupe before using it in your saga. But I would not consider it a house rule.
In my Scions of Nathas high fantasy game, I wanted powerful items that didn't immediately disintegrate at the first perdo spell, so I put together some rules for them that grant them magic resistance. And yes this was deliberately also done to affect magic weapons passing through wards. I wanted magical swords to be more dangerous than normal swords.
The house rules were:
Charged items do not get magic resistance.
Lesser enchanted devices get MR equal to 1/3 (round up) of the total effect level (e.g. a device with a level 62 effect in it gets a magic resistance of 21
Invested devices get MR equal to half (round up) the highest effect level, plus one quarter (round up) of the effect level of any other effects (e.g. an invested device with level 20, level 10 and level 15 effects has a magic resistance of 17 (10+3+4).