In our current game, one of my players has come up with a good idea. I have vis occurring naturally here and there, not just annual stuff. He is intending to build magic items that will trundle off into the wild and, using InVi powers, find and pick up vis similar to a pawn of vis put into the item (the idea comes from the rock gatherers in Hermetic Projects). I'm fine with this as it'll take him a while to build the thing and quite an investment. My current problem is how much vis the thing can find. I'm running an average concentration of vis saga so I was thinking maybe 1d6 pawns per season, depending on the type of vis looked for. More chance of finding He in a forest etc.
Story wise, I'm looking forward to one of these things trundling along to some source of vis that is claimed by someone or something else. Any other ideas?
Redcaps would be interested in "free roaming" magic items, and I don't think there's anything in the Code stopping them from claiming items "out in the wild". Wandering normal people might destroy this freak of nature. Then, if you want to be nasty, there's Infernal Vis........
Stealing an item would clearly be a violation of Code. But basically everyone would want to steal the thing. But the infernal now there are a lot of fun ideas. For starters demons deceptions can't be detected as magic. That pawn of intello vis? Its actually 13 pawns of infernal perdo vis. What could go wrong? The demon could impersonate the item! Then it slips a note to the police and well... the police persecute an innocent magi damning them all to hell. (The fact that the magi suffers is incidental. 
)
Anyway, 1d6 pawns seems reasonable. Or actually 1-6 pawns decided as you wish. In normal circumstances.
Tricky, Lamech. The code doesn't really cover unattended items. Items in a Covenant, yes. In a lab, yes. On your person, yes. Free range will be something new in the Setting, and you can get quite a few stories out of "poaching".....
Maybe their haven't been a lot of explicit rulings, but its obviously covered under "magical power", just like your lab gear you are having shipped in. Your books if you have a mundane carry them, or a vis source that you got a claim on.
I like the idea of infernal meddling. That is definitely a good plotline. Thank you very much. As far as the poaching goes, there could be some stories there, including the tribunal case to set the precedent. A magus who comes across one of these things doesn't have to steal the whole thing, of course. Just take the vis it has gathered and let it go. The player magus would possibly notice that he's getting less vis coming in. Is it that he has harvested the local area clean or is the vis being stolen?
And what would happen if one of these things wanders into another covenant's vis stores and helps itself?
Thimothy Fergusson helps you here:
arsmagica.it/Cliffheart/riso ... Light.html
The concept has already been implemented in an adventure / saga seed
Thank you, Xavi. Powerful is your web-fu.
Thinking about it, Lamech, I think the closest comparison is going to be with permanent Vis sources. They are protected by the Code, but only if you "register" them. You have to let the Order know about the source, where it is, etc. Some Covenants do not do so, for fear that someone will poach their now very public source. In the same way, the item would be protected by the Code, if you let the Order (in the form of the Tribunal, I'm guessing) know about it. But, if you let the Order know about it, you risk a Vis Rush, followed by the Tragedy of the Commons, at which point you have wasted the Vis making the item. Lots of stories there......
Is the source "very public"? I've always imagined that Mercere merely logs the vis sources in their records and more or less files it away, only to be used if there's a claim in Tribunal or if someone tries to register an already-registered claim. It would do them no good to divulge the registrant of a particular Vis source unless the registrant wanted it to be made public. Bad for business.
Same thing with where magi and covenants live. They only have to know where they are and how to get there. There's under no compunction to say, "Oh, Obnoxium of Tytalus? Yeah, he lives in a hut where the Avon meets the Clyde."
Of course, that just may be how I see Mercere operating.
First, it's not well defined in canon. In a kind game, yes. In a more political game, lots of power in that sort of information, how happy have you made the Mercene? Second, Vis sources do not, as a rule move. A mobile magic Vis harvester is going to have to be public, or it might get "found".....
Such an item is going to freak out peasants and others in the countryside, too. That may not be a good thing.
The reason why my player wants to make these devices is because of the way I have naturally occurring vis in my saga. As well as the permanent sources such as those described in Covenants, I have the odd pawn of vis turning up because of natural magical cycles. e.g. a pawn of Pe vis might turn up under a rotten log and, if not gathered, would be used by natural magical processes. It's this vis that the magus wants to collect with his machines. Because of its transient nature, this vis can't really be claimed by a single mage.
Some vis sources require interaction with an actual person with actual intellect (even a negative int), and some require a magus to attend.
Others require a story, since they are things such as challenging a magical guardian or such like.
And TBH, it'd be not unlike a member of the fae, or even a hedge wizard, to steal the device.
Yup, he's thinking of making it with an InVi enchantment so it collects the type of vis it has inside it. That means that it might even wander into a monster's lair and try to grab the vis that it is guarding. Squished device, upset beastie. I think he's going to find these things just enough use to keep making them and just enough trouble to keep the covenant in a bit of trouble. Mwa-hah-hah!
Remember that sometimes the vis ARE the creature. You'll end up with one getting stuck at the aegis as it tries to drag a low might critter back through 