I found some references to Container as used as a target, but not quite what i was looking for as a small possible hermetic breakthrough.
I am thinking of effects where the item itself is not affected by the magic, but the items within the object are. Akin to a T: Room effect, but specific to the contents of an object. T: Individual would be for the object itself, but not the contents, or is there an understanding that T: Individual it also affects the contents, such as a purify spell on a cup of wine.
It might be that this concept has been thrashed out before and I've missed it, or that it is too powerful in terms of working around the idea of an invested device. Or is it disallowed as the magic would be affecting a target that is unseen by the magus? But then how does room work?
It seems a reasonable extension of hermetic magic, without being overtly abusive. As it is so similar to Room, it would be of the same magnitude.
eg. A backpack or chest which makes items lighter when placed inside it. Or prohibits food from spoiling, or purifies the contents.
I see it similar to the Ring and Circle rules, and i was working in the same rule.
It could sized to +1 part to affect any thing contained after the spell casting (just like the typical spell of trapping bag or reducer bottle)
Well, first, in my opinion most containers do fit the description of T:Room (a large shallow bowl might not, but a chest definitely does), and in most cases T:Group would work as well for the contents. Although in the case of Room, as with Circle, there is that nagging problem about whether they can be moved without interfering with the spell...
I think a Target: Container, covering the contents of a container but not the container itself (similar to Room), with a level equivalent to Part and limited to one standard individual of the Form(s) for the contents, would be a valid goal for a Minor Breakthrough, with the understanding that the container can be moved without interfering with the spells on the contents. Bigger containers would be covered by increases in size, although at this point they become equivalent to the Room Target.
You might also want to look at a Duration:Container, equivalent to Duration:Ring, so that spells can last as long as the items are in the container. An additional Minor Breakthrough would be needed.
Interesting. The chest might fit the bill, because of the regular shape, and presumably a lid.
What about a sack or bag? Well defined limits but irregular shape so hardly covered by RAW.
Or a covered wagon? Too flimsy IMHO, but it could be useful.
A tent?
I could see the box or chest be a Room with no further ado. And then perhaps a Minor Virtue - like Road Magic - could cover 'Container Magic'. I could go for Container being same 'level' as room, covering any enclosed volume (like bag, sack, barrel, tent, covered wagon, ship hold). But the amount covered by container should be significantly less than Room. I'd go for a Base of a large barrel, perhaps like the mass of a Size+1 person. So you'd need further magnitudes added for size to affect the contents of a covered wagon or ship hold.
Really useful for a merchant. I'm fiddling around with a Mercere merchant type magus so...
Thanks for the feedback, appreciate it. The point of Container also being a Duration is interesting, but varied from what I had in mind. Perhaps its worth re-visiting the Seal duration sometime - Seal is a great evocative concept (I'm jealous of that idea).
Here is what I'm thinking as the form:
I went with size +0 as base as I do not want massive areas to be abused by this, and I was also keen to see the effect equivalent to Room, as the posters above have mentioned that Room has already sometimes been used for this purpose.
One of my favourite thing about the spell/effect design rules is that your magus is totally free to make up their own RDTs. You don't need to make a breakthrough in order to use a novel Target, for instance. Breakthrough's are more about formalising and optimising that Target.
I would be inclined to treat Container as Room +1 as it has some elements in common but is slightly enhanced and I'd allow cages, bags, sacks, bowls, etc. I do the same for things like open spaces or areas of effect - there's nothing impossible about affecting a poorly-defined area, but it's harder than doing it to a well-defined room, so it's Room+1.
If someone wanted to pursue the breakthrough, I'd set it the Container level the same as Room.
Your 'open area' touches upon a sensetive subject for me. Some spells have T:Room - Summoning the Distant Image and Winds of Mundane Silence IIRC comes to mind - which bu the letter of the rules don't work outside. What to do here? I know a magus can just design and invent a spell affecting an open area less well-defined than a room, using Room+1 magnitude. But what if one has those spells as written in core rules?
I tend to allow the use outside, but affecting an area much smaller than one could get away with were it in a room.
There are several canon spells that work like that, even tho' they go directly against the Target Guidelines. Anyone's call as to how to rule on that one.