I have a question regarding interaction of Ring target and magical item.
My mage wants to craft a magical item that will allow a servant to cast "Ring of Fertility" (CrHe 30: base 15 - bring a crop to maturation with a day or a night, Duration: Sun (+2), Target: Ring (+0), Range: Touch (+1)).
Normally, the mage must maintain concentration as he is drawing the circle, at a maximum speed of 5 paces/rd. If the circle is already drawn, he must trace the full circumference at a maximum speed of 10 paces/rd (paraphrasing p112 core rule). The mage will engrave once the ring in stone, spending as long as he needs to do it properly (about 15m diameter, 50m circumference), probably even melting bronze or other metal into the engraved circle to make it quite sturdy to resist robust farmers footsteps
Question one: Do you still need to maintain concentration when you are casting the spell with an engraved ring ? The way it is written in the rules is a bit ambiguous as it is only written "Trace the full circumference" without mentioning the concentration, but it might have been omitted because it was spelled out a few sentences before.
Question two - part I: If the spell is cast by a magic item, how does "Maintaining concentration" work ? I am a bit puzzled by the interaction "maintain the concentration of spell you don't cast" (whether the user is a mage or not).
Question two - part II: Can the item "maintain concentration" if the +5 modifier as been set in the enchantment as the holder of the item trace the circle ? I will be likely to agree as it seems a fair use of the "Maintain Concentration" option.
Question three: Is it possible to teach Concentration skill to a grog the same ways Finesse can be trained ? Very likely, the use is limited, but it is not Gift dependant or even magic related (Art of memory uses Concentration for example).
There are many ways to trigger an effect in a device, and none of it appears to be explicitly linked to a D: Ring. So it is simple to conclude, that a device effect just cannot have D: Ring, and be done with it.
Allowing it requires some creativity of the troupe. They could make tracing the Ring, just like for the spell, a part of the conditions to trigger the device effect, and with that proviso allow D: Ring with that effect.
If you allow the creative solution I outlined above, you better require also the concentration when drawing/tracing the ring. Otherwise you might end up unbalancing D: Ring for your saga.
An item by ArM5 p.99 can maintain concentration for an effect, but not for a triggering action.
As Tellus already said above: just about every grog - perhaps unless he has Flaws like Short Attention Span - may learn the General Ability Concentration.
I'll reiterate much of what has been written by others, above; though in some ways my view differs.
It seems reasonable that if you want a T:Circle/D:Ring effect in an enchanted device, the device should trace the circle as part of invocation of the effect. Being the ring, of course, also qualifies.
"Item maintains concentration" is something that has to do with D:Conc, not with the actual casting.
Note that concentration is required when casting any spell, including a D:Mom spell. It's just that it's trickier to maintain if you have to walk for three leagues while tracing a really large circle. But if someone smacks you on the head while you are casting any spell, even while you are fast-casting it... you have to roll Concentration, or lose it. Since in general items seem to automatically take care of concentration when producing effects (i.e. a the user of an enchanted wand can't get "distracted" when invoking an effect instilled in the wand, even if smacked on the head etc.), it seems reasonable that the same should hold for all types of effects, including Circle/Ring ones. Then again, this might be unbalancing, in that really large Circles/Rings are very powerful, and one of their limiting factors is indeed the risk inherent in tracing them. So, I'd probably require the user of the item to concentrate as if he were casting the actual spell.
And of course, as everyone noted, Concentration is something that virtually everyone may have. It's useful when praying for miracles; when standing guard all night; and to muster the focus for a second attempt when the first was a failure.
I don't buy that. If Ring effect cannot be enchanted in item, it should be clearly stated in the rules, which is not the case. And I am not looking for D: Ring, but T: Ring. The duration is Sun.
That's sound reasonable and does not require any house rule.
The magic item holder must trace the perimeter of the Ring with the item at the same pace a mage would do. If there is no pre-existing ring, he must draw it - with adequate concentration roll (and in this case, unless specifically trained a grog would not be able since he would not know what symbols to draw), if there is a pre-existing ring he only need to trace the perimeter (and thus does not require to have any knowledge of magic).
It is a kind of follow up tothis discussion on Standing Stone. I could see that as a minor virtue the ability to create permanent and robust Ring, as well as to use them without having to draw them. You spend a season (or more) creating the Standing Stone (probably a MuVi effect) enabling user with the right virtue to use is for their Ring base spells.
So what we talk about shall be an effect with T: Circle then, right?
So such an effect would have to get its Target defined by a specific action at the time of casting.
But by ArM5 p.98f Designing the Effect, a device effect has no casting, no ArM5 p.81 Casting Total and no need for a magus present at all. It just has a triggering condition, which can be "stepping on it" or such. So, by the books there is no provision for putting a T: Circle effect into a device.
So you can address the same creative troupe, that allows this Minor Virtue, to define specific triggering actions for devices with T: Circle, as we all have suggested here. Easy, isn't it?
I personal would be more worried about the warping your Ring of Fertility will bring to the crop if used for a longer duration then if it can be used without having to manual redraw the circle 2x a day.
In opposite to what One Shot says there 2 enchanted items in Hermetic Projects that have duration sun target circle with the constant effect! Check page 44 and 71 of Hermetic Projects for them.
So unless One Shot or someone else can point toward a errata that they where changed the idea of the first posting sound legitim.
(I know some people prefer if Hermetic Projects was never be written but because the book exist it is canon and would have to be excluded via house rule)
The device is the caster. A valid (and I think in this case necessary) triggering condition could be "completing a circle" (meaning the device has been moved from point A back to point A, via a largely circular path). That probably shouldn't be the entire triggering condition, but would probably need to be part thereof.
I'm usually cautious about devices designed with D: Ring and/or T: Circle, but this is not really one of the problems I see.
These two enchanted device effects (p.44 Convening the Circle and p.71 The Ship's Hearth) are canon, and show, that ArM5 has authors continuously applying and expanding rules creatively. There may be more of such effects, indeed. These effects can be triggered - but as usual with published effects we do not know their triggering conditions.
AFAIK there is no guideline, how to define triggers for devices with T: Circle targets. So, by the books there is no provision for putting a T: Circle effect into a device. And one still needs to rely on the creative troupe to provide that.
This sounds reasonable.
But there is already a problem with both HP p.44 Convening the Circle and p.71 The Ship's Hearth: the devices holding these effects - the large wooden rings holding ACs and the brick and mortar ship's hearth - cannot be moved without destroying them. You need the creative troupe here already, to make up a working triggering action for canon devices.
Sadly I don't find the story I remember to have read in a ARM book in the past where a flower garden was under a constant magic effect for a longer duration that then mutated into man eating plants.
Also keep in mind that you have problems in crafting larger objects because you either have to use a special mobile lab, a temporary lab that is destroyed once the object is finished or have the item small enough to get it trough the lab doors, at last till the mage know about the minor mystery Hermetic Architecture.
So I personal would go with a staff that require to draw the circle what need a concentration roll of the user instead of a fixed circle with a constant effect.
Edit: Ohh and don't forget that such a item could fall into the rules for magical income of your tribunal.
But the Subtle Chain is from a 2005 book, when Wards where not recognized to require penetration. Today and as written, it is just useless: before bothering with it, you need to further modify Philippus Niger for your saga anyway.