In trying to preempt an argument with our group I've tied myself up in knots on this. Could someone please confirm (or deny) that this is how this would work please?
I've got a magic item that has a Concentration duration effect in it. The effect has the "+5 Item keeps concentration" modifier included. It also has unlimited uses. I could cast this effect any number of times and the item will keep the concentration on the effect no matter how many times it's cast, i.e., the modifier for keeping 100 spells going for a human magus would be redonkulous but it doesn't matter because magic items just work.
To put a spin on it that may make it more palatable; Item maintains concentration is the same level as duration Sun. I think that we wouldn't be having the conversation if the effect were duration Sun, Diameter, Moon, or anything else.
I'm confused a bit by the question, and it appears that there are two uses of the concentration being mixed into one question (?). Apologies if I am misreading. But essentially Yes, magic devices just work (subject to penetration, aura, etc).
When an power is enchanted into a device with "Maintains Concentration" and a "Number of uses N", then yes that particular power can be used any number of times up to N and the duration of the effect will be limited to Sunrise and sunset, at which time the spell expires or the device use must concentrate to maintain application (I thought that was a limit in Conc effects at sunrise/sunset in RAW?). I don't think unlimited uses should not really change any part of the discussion.
i.e. the wand casts a spell to levitate a bowl for R;Touch, D: Conc, T: Ind; with 2 uses.
the two bowls touched float till sunrise/set or if the wand holder concentrates to continue the effect through sunrise/set. The extension of time does not require a use per day, but requires concentration from the source of the spell. ie. the Wand must be present during the concentration. I think it is fair that even the user of the device might be different, as long as the device is present.
the same Wand of Levitation with unlimited uses would need to be present and used to maintain all effects where it has been used during sunrise/set for the previous uses too. Might be a heck of a concentration roll needed for the wand user if too many items need to be done at once, but given sunset takes a bit of time it could be considered automatic as long as it is not 20-30 levitating items, as that will take some time.
The second part of the OP seems to be asking about an item which maintains concentration for spells cast by the device holder. That's a cool item which I think has been created in the source books a few times.
i.e. A Ring of Spell Maintenance should have a few other limits set by the Rego Vim properties of the maintaining spell which is enchanted within it. All the limits of the ReVi effect apply, including what combination of levels each instance of the Ring's power can sustain. Typically a ReVi power like that will have a specific effect to target Duration: Conc effects, up to a max level. There has been some chatter about the Range of such effects, and I think that has been clarified on the forums before, although I can't remember what was ruled atm, particularly with regard to the device affecting spells through the Magi's own Parma. YSMV.
And then an Unlimited modifier in the device means it just works.
ArM5 p 99, Concentration starts to wear off at sunset.
Now, we're talking about lifting a stone and keeping it there with Concentration. Lifting a second stone, ditto. And a third, fourth, fifth... Then you choose the 2nd stone and move it elsewhere. When the Sun goes down, all the stones start to fall but you can concentrate on one to keep it up, assuming you've reserved a use for that. Or you could have Unlimited Uses and Environmental Trigger to keep them all up.
So the consensus is Effect Modification Concentration can maintain concentration on all the "uses per day" of the device, even if simultaneous.
Interesting that you're suggesting an additional use is needed to maintain concentration, when concentration at sunset on a spell does not need re-casting of the spell.
Ah, thats right the Environmental Trigger was the thing I was forgetting. Is that where a use at sunrise and sunset is noted as being needed? I have no book here.
I disagree that an enchanted effect with D:Conc for which the effect maintains concentration can be used this way.
This is a single effect, which to me means that it can only be active on one target at a time. When you activate it on a specific target, the effect is "busy" maintaining concentration on that target and cannot be used on a different target without terminating the effect on the first target. D:Con is not a "fire-and-forget" duration.
The item does not have a mind; nor does it have a memory to keep track of active targets.
The number of uses for a D:Conc effect is useful in determining on how many targets you'll be able to use it on for the day -- but only once at a time. In this, the last sentence of the "Concentration" effect modifiers of the enchantment rules (ArM5 p.99) is telling: "This allows the wearer to end the effect at will, and start it again if the device still has uses left."
Otherwise, you end up with absurdities like:
You have an invisibility ring that gets passed around. Each person activates it, making himself invisible. Without terminating the effect, he/she removes the ring and pass it to the next person. After all, the range is only applicable when activating the effect and the item maintains concentration, right? And so on, until all the group is invisible. Only need to pass the ring around again if people want to stop the effect before the next sunset/sunrise.
YMMV
In our saga, every time that the wearer uses the magical item, the "maintain concentration" modification is transfered to the new spell and ending the previous one.
If you want to have several copies of the same spell simultaneously a diferent durations like Diameter or Sun is necessary.
Sorry for any confusion. I did indeed mean a single Conc. Duration effect that the item maintained, not an item that maintains my spells for me. My Bjornaer has a phoenix (well, an eagle but I bought a bunch of Virtues that we're calling "phoenix") heart beast with the Elemental (fire) Inner Heart Beast initiated. I've got a talisman in the form of gauntlets for my birdy feet that I want to instill an effect that wards anything I carry against my +30 fire. A Sun Duration effect would not work in this case as I'd like to selectively not burn people I like and burn people I don't. I don't want to have to wait until Sun to burn someone I picked up and later decide they need an education....
In the din of the gaming session last week I heard someone ask "how many times can an item concentrate?" and I don't think it was really addressed so I'm expecting to have to defend whatever it is I come up with. I can probably sell the group on "what's reasonable" as it probably won't be more than one or two a day.
I agree with Jonathan here, as "unlimited" is expensive enough in item creation terms to be cost effective for it's utility and potential for silly abuse.
The use of the Invisibility Ring is not as broken as it initially appears if you re-consider the example to be a wand. An item can be created with a R:Touch, D:Conc, T:Ind, Unlimited uses, and Item Maintains Conc - knowing that if the effect needs to be removed or extended then the wand needs to be held and activated to do so. It is not a pragmatic item in terms of in-game flexibility, but I don't think additional rules are needed beyond RAW.
I (of course) respect each saga to their own, or even perhaps mine being the outlier.
I was going that way until I realized this only helps if you have the "use per day", which are costly.
Replace Concentration with D:Sun, it becomes pure RAW at the same cost. The real advantage over Sun is that you can cancel it at will. Well, some other way than simply removing it.
I am still ambivalent, that's a Troupe's decision IMO.
I'd argue the ring is entirely valid. The fact it maintains concentration means it has to be concentrating on making the target invisible. Since it's only means of detecting said target is by touch, when it's removed, the magic 'assumes' the target is gone, ceases concentration and thus the target becomes visible again. But that's probably just me.
I would note three important differences between Constant and continuous via Concentration. One was already mentioned: continuous via Concentration can be ended while Constant cannot be. The second one has to do with dispelling. Constant does not just get dispelled, it merely wavers a little and continues (see WoMS). Meanwhile the continuous via Concentration effect will just end until it gets re-triggered at the next Sunrise/Sunset. The third one is how MuVi and the like affect them. Continuous via Concentration is cast twice a day and so a built-in MuVi effect must have at least 2 uses per day, but Constant only activates once (not even once per day) so long as it runs and so a built-in MuVi effect must only have 1 use for the entire activation (it could potentially even expire).
AFAIK, there are no official rules on this, but, IMHO, an item can concentrate as many times as required. For example, if your character uses the gauntlets twice in a day, the item will maintain the effect both times, as the rules say. This has nothing to do with whether an item may maintain multiple effects simultaneously or not.
We decided a magic item can cast up to 13 simultaneous concentration effects based on the following "logic".
Concentration Duration effects wear off at sunrise/set.
Concentration effects last 15 minutes per level of ability.
For a human caster casting a spell at sunrise and having it last until sunset, without a roll, would be equivalent to a 48 Concentration ability.
For a human caster with a 48 Concentration ability they could cast, assuming no botch, 12+3+3...=48 or 13 simultaneous concentration effects.
Yes, magic items are not humans, but it's a number.
I'm sure we'll find a way to keep arguing about this in our group. YMMV.
