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Rule Interpretation of The Earth's Carbuncle


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I need to bring up the spell The Earth's Carbuncle as Dirk have it and it recently was part of a discusion in the Atlas Game forum and now I wondering how we should handle it in our group.


From the definitation they ended there the part Target is actual needed because it affect part of the earth and the size of this 1 pace circle only affect 1 person but its one of the spells that dont need finesse to place.

The problem comes now in if someone change the Target of this spell as it is i.e posible with Flexible Formulatic Magic.


What happens when the Target is incresed by 1 magnitude to group/room?

In the Atals forum was suggested that group would be multiple 1 pace circle are generated but only affect 1/2 of the usual group size, something I couldn't follow entirely.


What happen whan the Target is reduced by 1 magnitude to individual/circle?

I doubt individual is possible with the defination abouve but circle sounds entirle reasonable.


Now my question is how we should/ can handle this within our group.

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To me the original spell works fine, aiming at the ground below a target, sharpen the stones and send them flying.


Changing target to group would, to my mind be one or two possibilities, as you say yourself. Larger area or several smaller circles.

To justify a lot of small circles though I'd say some finesse would be required, otherwise I'd expect a lot of stones to just randomly erupt here and there. The larger circle wouldn't have the same requirement, but I don't know how large it should be able to become.


Reducing target is fine, but you get what you pay for I'd think, meaning:

Circle, you'd have to manually draw the circle first and then it can explode - in a fight I'd imagine someone might try and stop it, otherwise it's fine.

Individual: "The spell can affect a single discrete thing, such as one person or one object." This would be object, since you can't coerce stone from a body. You could do it on a boulder I'd think, sending a shower of stone every which way. If someone stood on it or cuddled it I might imagine it'd be very painful but otherwise I'd think the damage would suffer as the arch with which the stones hit is wider.


It's just me though, there may be a larger issue I am not seeing.

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Schwarzbart: This is how I see it:


Amul in the forums seems to consider Target and the Size modifier freely interchangeable, i.e. "If you want the Earth's Mighty Carbuncle to affect a group's worth of area, then you need to make the same magnitude adjustment as if you were targeting a Group rather than an Individual. Whether you call that a Size increase or a change in target is irrelevant."


I don't concur with this assessment. To me it seems like the Targets are what you begin with, and they operate in a conceptual register that is quite distinct from the mathematical. So you can't have a Group target with that spell, since doesn't make sense to speak of a "group of the earth"; the target description also says that "the group itself must be separated from any other things of the same type", which seems to preclude this interpretation altogether. If the earth's consistence was not homogenous, then maybe it could work, but that's a long shot. Insofar as that's not the case, the spell would have to be Target Part.


It is only AFTER you have conceptual register figured out, i.e. after you have selected target Part as is conceptually feasible, that you look at the mass-based size system in the book, and add magnitudes if you want to insure yourself against targets larger than that. But this doesn't interest you, since Flexible Formulaic Magic only works on Target, Duration, and Range - so no size bonus allowed on Part.


On the other hand, it seems reasonable that you should be abe to boost the size of that spell with FFM. I also would wager that if you look at the spell guidelines, you are bound to find some Targets that are conceptually muddly.


SO: I would allow you to get the size to 10x the base Individual, which is for stone is 10 times the MASS of one cubic meter of stone. What I *think* confuses both you and some of the people at the forums is that the base individual for Terram is expressed in volume (so ^3) whereas the Size bonus is expressed in mass. As the book puts it in 113, "a five level boost to a Corpus spell would allow the magus to affect a giant up to fifteen feet tall, not sixty feet tall". This is why the area of the Carbunkle circle doesn't expand linearly (it doesn't expand downward, so area, i.e. only ^2), but my maths is frankly not up to the task of figuring the exact calculation out at this hour.

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I actually didn't pay attention to mass or size really, just the phrasing :P

I think I see part of your point though, even if the mathematical reasoning eludes me. That said the math itself seems doable.

If we treat it as a sphere full of dirt/earth/stone and want to know the radius for ten time the volume then the radius would be 2.15 times the initial spell's radius.

If we (perhaps more reasonable) say that only half the sphere would be dirt (we are aiming at the ground below someone's feet) then the new radius would be 2.71 of the initial radius.






The original spell's volume:


4/3*PI*R^3=Volume, R being the original radius.


The suggestion, as I read it would allow for 10 times the original volume.




meaning: 4/3*PI*r^3/10=Volume which then = 4/3*PI*R^3 , the Original R in the last bit.


Shortened: r^3/10 = R^3 or r isolated, r^3=R^3*10


making it: r=R*10^(1/3) = 2.15*R (the third root of 10)




IF however only half of the circle is dirt then the volume we used is only half the -real- volume.


making 4/3*PI*r^3 = 10*2*Volume - It should fit now, right?


Shortened: r=R*20^(1/3) = 2.71*R




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Yeah, don't mind my mathematical reasoning - it tends to work differently than every other human being's :D


Thanks for doing the calculations, Adrian. That doesn't quite fit Schwarzbart's canon 3x3 square, though, since your 3 pertains to the radius rather than diameter. But switching it to diameter would yield the same result, wouldn't it, since it would shift both the original spell and the new one? My queer reasoning says that a diameter 3 circle should be roughly equivalent to a 3x3 square, so we could agree on that, couldn't we?


I also think diameter is what the original spell description means, because a] that's the intuitive reading of a "1-pace" circle and b] because a 1 meter radius means a 2 meter diameter, and that's pretty much for just one person. That's without any of the volume calculation going on in the forum thread.


Edit: Oh yeah, and I think circle is fine - you'll just have to draw the circle, keeping concentration, and somehow avoid the explosion yourself :P

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We general have jumps in Ars Magic for size.

Usualy it looks like this: 1,3,10,30,100...

So its never a direct mathemtic function when your working with different size in this game instead you have to keep the 1,3,10 following in mind.

I.e room size is considered 10x10 paces and structure size 30x30 paces.


Ohh and dont forget that hight dont realy count in the Ars Magica 5 ruleset as fare I have seen it.

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Where do you get those numbers from? The core book p.113 states that structure is 10 base rooms. I suspect, if those numbers are stated somewhere that is canon, that the discrepancy is because the 10x is IN TERMS OF MASS, which would translate to roughly triple the volume if density is constant (I think). That would not yield 100 as the next volumetric number, so that's why I would like to know where the numbers are from. It's also incorrect in the sense that the maximum sizes for room and structure are not defined in terms of mass at all, but in terms of volume, i.e. "large enough for 100 standard individuals" for room.


The aforementioned issue is also the reason why you are wrong about the height - mass tends to go with volume, i.e. height included. The base individual for the "stuff"-related form Terram is expressed in cubic paces (p. 152). So height does count in that case. It also counts in the spell we are talking about, although implicitly, as is taken into account in the forum discussion you linked, and it also counts when figuring out size adjustments, because those work with mass.


I'm starting to get a clearer understanding of what this confusion is about. Ars Magica mixes and matches three complementary but non-integratable systems for determining the "size" of something. First, there is the conceptual system, which works in terms of things like "group" and "part" and the base individuals of most forms, i.e. "adult human" for corpus or "mind" for mentem. These cannot be integrated with the two mathematical systems without doing violence to the semantics, intuitiveness, and flexibility (with the exception of simple countability, i.e. "two minds"). Second, there is the volumetric system, such as with the base individuals of Herbam and Terram, which usually works in terms of cubic spaces. Third, there is the mass-based system, such as with size magnitude increases and maximum base Target sizes. This system bases the mass calculations on the volumetric system, (i.e. the giant example above presumes that the human to be enlarged is three-dimensional) so it is in fact more like a subsystem.


It might be a good idea to do away with the mass system entirely for the sixth edition, because this is goddamn confusing. Then you might need a different Size bonus system, though, but as it seems that even the archpeople at the official forum don't get it, it might be worth considering regardless :P


Edit: But none of this changes our conclusion, which to my understanding is that your boosted spell would have a diameter of 3 paces, so might hit several people if they were close together.


It also doesn't change this: if we 10x the maximum mass of a spell's Target through a magnitude increase, and we only enlarge the target volume in two dimensions (and density and the third dimension stay the same), I think we'll end up with approximately triple the original diameter [or diagonal in the case of a square?].

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Its the official numbers from TMRE p97


Boundary = Structurex10 = immense room = 100 paces x 100 paces

Structure = Huge x 100 = Ind x 1000 = huge room = 30 paces x 30 paces

Room = Huge x 10 = Ind x 100 = 10 paces x 10 paces

Huge = small room = Ind x 10 = 3 paces x 3 paces

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Yeah, ok, that seems to do away with mass entirely (and any pretension of mathematical coherence, in fact:D). That's the mode of presentation they should have gone for in the core book, probably.


So I would suggest we go with that table from now on, and replace any consideration of the core book's overcomplicated system with this one.

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actual the 10x10 paces for room are interpolated from me because they are missing in this official table but for boundary you have the official numbers again

boundary = Structurex10 = immense room = 100 paces x 100 paces


(But I think I have seen the 10x10 paces for room at a other location already)

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wellp, that was somewhat easier :P


Looks like we are working with area rather than volume/mass, which is fine. Easier to work with at any rate. - And in the case of the spell in question, very close to the MASS suggestion. 2.7 is almost 3, after all.

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