Handling Multiple Remote Sensors

If a player casts a hundred sun duration Prying Eye spells in different areas how do you handle what he sees? I have two possible solutions that I see.

  1. Caster needs to make a concentration check equivalent to Maintaining another spell (base Hard (12), +3 for each spell beyond the second) to be able to perceive through multiple sensors simultaneously
  2. Assume caster can see through all the sensors simultaneously but require Perception checks that increase the ease factor with the number of sensors to notice something

Thoughts? Alternative ideas?

The spell only works as long you touch one of the walls of the room you want to look into. Assuming that your player is not capable of touching hundreds of walls at the same time I would say that its a non-problem.

However I would probably require my players to roll concentration to make out anything useful for a few rooms (2 most likely) and just rule that the character is overwhelmed with sensory information if they managed to pull of more castings. Keep in mind that target of the spell cannot suppress the images unless they cast Supressing the wizards handiwork or a spell with the same effect so its not possible to scan for relevant information and then choose to only see that.

Not true euphemism. There are dozens of spells that work when the range between you and the target varies. Range is only important at the time of casting.

Interesting idea. I would probably limit how many sets of prying eyes you can use at the same time. Like looking at a wall of close circuit cameras. 1 ok, 4? easy. Control a dozen? Harder. A wall with 200 cameras? You are quite easily unable to see anything at all because circumstancial stuff keeps distracting you. So concentration rolls to use the spells (not to cast them), harder as you increase the number of cast spells.

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the reason why I say that you need to touch the wall is because of the description of the spell:

You can see inside a room, as long as you can touch one of its walls. (from Ars Magica core rulebook page 144).

The way I read the description you need to be able to touch the wall of the room to be able to see inside it.

There is also a pretty big unanswered question in how exactly the seeing works and we seem to interpret it differently. If the spell works like looking at a tv screen I would a player to keep watch over a similar number of rooms as what you recommend Xavi.
In my answer however I assumed that the vision you get of the room replaces your natural vision such that a view of a single room takes up your entire field of vision and that each subsequent casting superimposes each image on top of each other. I dont strongly favor either interpretation but I have very different opinions on how many castings it is possible to keep track of depending on which of our two interpretations hold.

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Yes but as per the opening post this is a sun duration variant and the question is open to multiple generic sensor spells in effect at the same time.

I am tempted to rule that each remote sensor in effect is a distracting situation as the caster sees and hears things from multiple locations. The distraction level would be at least the equivalent of "Answering a single easy yes/no question" which is Hard (12) and adding +3 for every extra sensor. This concentration check would be required to cast any subsequent spell while the sensor(s) is distracting the caster. This is presumably why all remote sensor spells seem to have a concentration duration.

Sound fair?

But for the sake of argument, let us suppose that we have a lot of intangible tunnels set up to multiple rooms with which we have arcane connections...

Then the caster is effectively in touch range of multiple targets which is fine. How does that apply to remote sensors?

The spell description is pretty explicit that you need to be able to touch the room not just to cast the spell but also afterwards in order to sense the inside of the room.

The description doesnt state that you have to actually touch the room, contrary to what I wrote earlier. But according to the description you must be able to touch the room, which really limits you to rooms that are within arms reach. That's presumably why rgd20 suggests intangible tunnels.

Prying Eyes was just an example of a remote sensor spell and not the focus of the question which is about remote sensor spells in general. It is not breaking any Hermetic limits to invent a sun duration remote sensor spell that does not require the caster to touch the room.

Hmm I see. Well okay then. I stand by my earlier comment on how the effects that multiple different sensors have on a caster is highly dependent on how you interpret the effect of the spell, namely:

  1. Does the sensory image from a single casting of the spell take up the entirety of the casters field of vision
  2. Does the sensory image from a single casting of the spell only take up a part of the casters field of vision in a manner such that the caster can view multiple different castings at a time without one casting interfering with the other.

I would also add that the effects are in both cases are highly dependent on the contents of the rooms, if they are all dark I would say that a single person can look into as many rooms are they want with no detrimental effect apart from boredom and if the rooms are all highly active then as little as 1 room might be possible, with a sliding scale of difficulty in between. In other words I dont think you can set a single fixed check for adding more castings.

If you favor interpretation 1, as I do, then adding just a single room beyond the first will be pretty much useless as soon as something happens in both rooms and probably force a check to avoid nausea or other effects from sensory overload might be called for.
If you favor interpretation 2 then I would say the issue is primarily one of awareness (and Awareness) to be able to determine how much detail from each room the character is able to accurately pick up from the mess.
I think concentration checks are only for casting the spell as long as its duration is not concentration, because by the time the spell is cast you really don't need to do anything to maintain it and the issue is primarily one of how you deal with being affected by the spell. I might require concentration rolls to cast spells while monitoring one or more rooms with a lot of activity. Also a character under the effects of many casting will probably need a guide as their ability to view/hear their actual surroundings will be significantly impaired.

Could you base how many remote sensing spells an individual magus could simultaneously process on his/her Awareness score? Could a talisman or familiar help process the sensory information with the right power or enchantment? Can a magus create a CrMe/MuMe(?) spell that enhances his mind such that he can process all those spells?

This is a pretty good representation of the distractions. For my work I've had to watch security cameras while also having employees walk up and ask me questions, and you miss things... But as was mentioned earlier, the big crux is how the spell effect 'manifests'. It could be replacing your vision, which means that multi-viewing makes you nauseous. It could be more like a security-feed system, in which case you just miss things most of the time.

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yesterday my wife pointed out to me that there is actually a third option:

the spell takes up the casters entire field of vision and any subsequent casting replaces whatever was in the field of view previously, meaning that the previous field of vision is lost and as such that it is only possible to be affected by a single casting of the spell.

I think another option apart from changing your mind to have greater capacity to have fields of vision or to maintain concentration on multiple fields it could be possible to design a version of the spell. In essence having the field of view granted by the spell take up only a part of the casters natural field of vision is like only affecting a Part of your sense of sight. I dont think just adding a Target: Part would work as that would still fill your entire field of vision with only a part of what is visible inside the room. Maybe adding something like a Rego or Muto Requisite to shrink the granted field of view or a different base level for the spell because it is in essence a much more flexible version of the spell.
Another alternative entirely is to use enchanted items conveniently shaped like CCTV screens, such as mirrors and have a monitoring room with all the enchanted mirrors each looking into a different room.

My 2 copper pieces...
The way I see thing, such spells directly send information to your brain and to some degree, overlap with your senses. And that for just one spell.

When you have multiple casts, I feel it should be like trying to follow X films a the same time - but each film taking your entire vision field (like Euphemism suggested it): sensory overload.

The spell has to been designed to have an on/off switch, nor to be tune down. So I think that the mage should make very hard Concentration roll just to be able to do anything and will probably loose fatigue level just to be functional.

I think after casting four or five of them, he will realise how pointless it is. So he should design a spell covering a larger area (Group or Structure) and allowing him to jump form one part to the next.
It it truly different areas he want to keep watching, he probably will have to resort to magical item with multiple casts, maintaining concentration and either Suppressing the Wizard Handywork or a ReVi allowing him to select one of the many instances of the spell to be viewed/displayed.

Maybe through the Art of Memory and an adequate spell it could be possible to "store" the vision of each spell in different "room" and consult them live or at a later stage - walking in the Mind Castle (I forgot the name given to the construct) would be akin of walking amongst the various locations screed by the spell.

Yet I find difficult to consider being able to follow many spell at the same time.

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All referencing Prying Eyes rather than the topical spell since I don't have the rules for that topical spell.
My RAW interpretation: So, unless he actually designed the spell as a supernatural sense (Target: Vision +4) then he doesn't have it superimpose over his normal vision. (In fact, I think Prying Eyes at T:Vision wouldn't work at all.) The default Prying Eyes spell doesn't replace your vision with the other side of the wall, it gives you the knowledge of the visual species on the other side of the wall, which your brain then interprets. Casting a T: Part instead of T: Room wouldn't really clean that up either. Having multiple sensors out spying on rooms just sounds like sensory overload : Turn on a dozen rock ballads at once and see how easily you can filter them. The spell kind of feels like a mental block of security camera feeds.
Now, there are possible uses: If most of the rooms are just empty and unchanging all the time, the mind of the magi will probably acclimate to them until something notable changes, like explosions, someone teleporting in, or someone rearranging the furniture.

The use of Art of Memory is an interesting idea but I don't think it would work easily. Memorizing something for art of memory, without a spell, seems to require pretty focused concentration... so somehow sending the "input" directly to the memory palace probably wouldn't work without a specialized spell. So then there's the spell to create a locus, unfortunately that requires examining the item, room, conversation, etc too during the casting of the spell though the concentration must be somewhat split between casting and examining (though it doesn't seem like in a meaningful/mechanical way beyond what casting a spell entails). That said I don't know if that being how that spell works rules out using art of memory and a remote sensing/locus creating spell that somehow bypasses the senses. At the very least I'd give it both Creo and Mentem Reqs and probably mags for complexity. (Prying Eyes uses base 1 and the Create Memory Locus spell uses base 5 so if I allowed this I would likely have it as Cr(In)Me(Im) 5 as base, then whatever R/D/T needed rather than using Prying Eyes as the base effect. But I'm really not sure I'd allow this sort of introduction of "headware memory.")

I suppose you could ask Ladon from the Hesperides section of Ancient Magic. It's hinted at that he's maybe a Daimon (or Daimon-like?), so maybe Trianoma left a Lab Text or spell tablet of a one shot Invoke the Pact of Ladon theurgy ritual (level 90?) that can grant a "watch 100 things at once" power mouldering on a back shelf of Durenmar...

Yesterday my wife was out of town. I had food on the fridge, but I thought I needed to cheer up my Monday, so I rented a movie and ordered pizza. At some point my wife called by the phone, and I was scratching my dog's belly, watching the movie, and paying attention to the porch, because I was hungry and expecting the pizza deliverer to appear at some point, all while talking to her. If we decompose anything one can do into that kind of mechanics of keeping concentration (that, if I recall, are for maintaining concentration spells going on) with these +3 steps, I was EF 21 concentration rolls without noticing!

I don't think the point isn't how many Prying Eyes spells you can maintain at once. I'm not sure how much attention you pay to your TVs, but I can certainly keep it turnt on and be somehow aware of what's going on, noticing when I have to focus on it. Re-reading the spell description the part that seems to require some effort and to concentrate is to change the viewpoint. So, yes, casting a handful of Prying Eyes as the spell comes out of the books probably deserves that 21+ EF concentration roll. But any variation of fixed duration, let's say Diameter or Sun, would just require the caster to focus to change his viewpoint. I wouldn't ever dare to require for a concentration roll, unless in extreme, stressful circumstances, like in combat or engaged in complex lab activity. Also I wouldn't start making analogies as "set of security tv monitors inside your brain", because thought it helps us making an idea of how to interpret the spell results, it obviates the fact that this is magic inside a game of magic. Don't you remember replying "it works because it's magic" back when you were children?

Anyway, Prying Eyes sucks. Any busybody magus will at some point come with something like:

Prying Watch of the Busibody Bored Magus, InIn 35, R: Arc., D: Moon, T: Structure
As Prying Eyes, with modified parameters, so you don't need to concentrate to maintain the spell, nor go around touching walls or limit yourself to one room. You might change your viewpoint within the structure by concentrating.
(Base 1, +4 Arcane, +3 Moon, +3 Structure)

Or even better! Do you want to know if dinner's ready at the king's kitchen, how it smells, if it's salty or dull, and the roast is well done? What's her maid saying in the basement and to whom? If the rider that just arrived have his coat wet and cold? Get some details regarding a quite intimately placed mole to blackmail the queen as she takes her seasonal bath? This is for you:

Prying Watch of the Busibody, Bored and Quite Possible Lascive Magus, InIn 50, R: Arc., D: Sun, T: Structure
As above but working for all senses (and cut down to Sun duration, because rituals).
(Base 5, +4 Arcane, +2 Sun, +3 Structure)

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So, I felt like people were being needlessly restrictive; then I recalled that in Transforming Mythic Europe there is a boundary spell that permits you to see through the eyes of every animal within the boundary.

Based on the mechanics presented, the magi has all of that sensory information available and can look through it to find specific things with a Perception + Awareness check with an ease factor of 12.

In a game I was running, I would just use the guidelines here. For anything less than an entire boundary of animals in terms of sheer numbers, I would probably reduce the ease factor to find specific things; I would also probably modify it for the size or ubiquity of the thing. A dragon that covers most of your viewing sensors isn't hard to spot.

I don't mind this explanation, however magic in Ars Magica has a very mechanistic approach, so some form of coherence should be maintained.
"Rego Handwavium" has always been the most powerful tool of the GM, though.

Base on the OP initial query, I see a difference between designing a spell that allows you to screen many places and using multiple times a spell designed to scry one area. The first spell has been designed to allow a global watch, akin to a radar, with the ability to focus on specific area whenever the mage wishes, the other approach is more like having a dozen speakers blasting their own music at full intensity and you trying to listen to one conversation.