I'd like to create an item to detect incoming ignem magic and snuff it out before it snuffs out my PC. Damn those Flambeau.
So, how about an item with 2 effects
Effect 1 detects the magic, analyses it and determines its form
(Base 5, +4 vision, +2 technique and form, +1 conc)
+5 levels - item maintains concentration
+2 levels - 3 uses a day
Total level 47
Second effect uses a linked trigger to target the incoming spell only if it is targeted on my magus and is ignem magic.
(Base 20, +2 voice)
+10 unlimited uses
+20 for +40 penetration
+3 linked trigger
Total level 53
Now i realise these aren't easy effects to enchant, but they could be done.
Would these item spot incoming ignem magic and snuff it out (i'm assuming the penetration total of the incoming spell is less than 40 and the level of the spell is less than 40).
I see an issue with the item using sense targets. (I see it because other folks have criticized me for doing the same thing in the past). One could construct an argument (and others have) that you need to endow the item with a sense of sight before the item could use a vision target. You'll need to make this call before you put it in your game.
In order for the item to use range voice it has to make a sound when it activates. You'll need to have a bell of extinguishing or something similar.
If these two issues are resolved I don't see anything wrong with the concept or anything else fishy about the implementation. In fact I'd think that in many cases you wouldn't need any penetration on the dispelling effect.
A less cool but also less fiddly option is to target yourself with a longer duration perdo vim spell that dispels any ignem magic that touches you. This doesn't protect your comrades and it shuts down your ignem spells while it is activated, but it doesn't need to have a triggering effect and it doesn't need to penetrate .
This made me think of a Necro-Verditius hooking an eye ( or entire head) to a device to "sense" magic.
You might need a third enchantment to passively sense magic. Your biggest problem would be that a spell that takes and instant to cast would work against you because you have a two ( or three) spells to get off before you would be effected.
Hmm. I don't think the environmental trigger is needed at all. "Touching fire" is a perfectly reasonable trigger without requiring any other effects. InVi would be needed for "touching magical fire", in my opinion, but frankly I think that'd be over the top for the item anyway.
Seems a little strict to me. Voice range refers to the distance sound carries, Sight range refers to line of sight or perhaps optical/visual/magical species which are, after all, what an Intellego spell would be detecting. Vision, as a target, must operate by similar logic. A blind magus should, I believe, be able to use InVi to "see" things, provided they're enchanted. He just wouldn't be able to see anything else.
This is, however, as you said a tricky issue. Whilst having items with eyes is very flavoursome, it's tricky within system. Besides, how would you bestow sight without a sight/vision target spell? The argument becomes circular. That said, carvings of eyes for symbolic effect would seem natural and almost expected.
You got away from the InVm by putting the trigger set to one thing. It also has weaknesses in that the Item much be touched by the magical flame to trigger. So it only works if the the Grog is ready enough for it to have a shield up. An attack from behind would burn the grog before it got to the shield to be dispelled. In reality it should be PrIg.
Not really in the realm of the RAW but a ruling that would make sense.