Promises, Promises: the Stone spell

Games Discussion Ars Magica
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I'm gearing up for a new ArsM game, and I thought I'd try my hand at designing an enchantment. The one that caught my eye was The Stone from Promises, Promises. What does this look like in ArM5 mechanics terms?

We know it's a huge stone, about 0.65m^3^ and so weighing about 1.5 tons. It protects the abbey "from breach and damage". Stephen's an experienced mage, but there's no indication he's a specialist in Terram.

How would we go about building this effect?

"Protecting buildings" isn't in the spell guidelines that I can see. So let's give the abbey the equivalent of "scale armour", which is "Soak" +4. Muto Corpus has that as level 20, so let's start there.

The enchanted effect is "Stone of Abbey Protection", +4 "Soak", level 54 (magnitude 11),
Base 20 (magnitude 4), Range Touch (+1), Duration Sun (+2), Target Structure (+3), +4 levels for twice a day with environmental trigger.

The Stone is soft stone and huge, so takes 15 pawns of Vim vis to open it for enchantment.

Stephen's lab total is something like Muto 18, Terram 15, Int +3, Magic Theory +7, Magic aura +5 = 48.

Let's be generous and say he knows the "Protect the abbey" spell (+10) and a huge stone is a appropriate shape and material (+7). That makes Stephen's Lab Total 65.

The Lab Total exceeds the effect level by 11, so Stephen can instil the effect in 5 seasons. (If he dropped the base level, he could do it faster).

He needs 6 more pawns of Muto or Terram vis to go along with it.

Do those numbers seem about right?

And looking at the material guidelines, Stephen could do exactly the same thing with a small (fist-sized) lump of stone, that would only take 6 pawns of Vim vis to open.

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To enhance a building so that it resists "breach and damage" (something that a building does naturally), I'd go with Base 3 (Change dirt so that it is slightly unnatural), with +1 magnitude to affect stone and a further +1 magnitude for an Herbam requisite so that the wood of the building is also affected.

Adding R:Touch (+1), D:Sun (+2), T:Structure (+3) and 4 levels for constant use (as per the insert in ArM5 p.99). Total level 39.

He could specify that the effect will expire after 70 years, doubling any excess from his Lab Total above the effect's level. So he'd only need a lab total of 60 to make this a lesser enchantment, spending only 4 pawns of raw vis and a single season.

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Unfortunately:

Effect Expiry (p. 99): Add the following sentence before the table. "Effect Expiry cannot be applied to Lesser Enchanted Items or Charged Items."

But still much easier than giving the castle Soak!

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True, forgot that.

If he made the stone as a part of the abbey, than he might get away with using T:Per , thus saving 1 magnitude. It might be a stretch, but could bring it back to something he might be able to enchant as a lesser device (level 34, so need a lab total of 68).

He might have had some help in the lab, either from an apprentice or his familiar (or both). Each of those helpers could reasonably give him +5 to his lab total, perhaps even more.

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Either way, it might be better to enchant it as individual+size, the op made no mention of reinforcing stone or wooden items inside the structure

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Using T:Ind with Size increases probably won't change to final level much. Unless the abbey is very small, it probably more than 100 cubic paces in total volume. So the effect would need 3 extra magnitudes for size.

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Personal: The spell only affects the casting magus or things that he is wearing or carrying. The target is thus never larger than Individual. (AM5 p.111)

R: Per, T: Structure doesn't work.

Also, even if R: Per, T: Ind with size mutliplier might work... this would likely require hermetic architecture.

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MuTe Base 4 "Highly Unnatural Change" as seen in HoH:S, p.37 with the spell Hardness of Adamantine. That is a +2 soak.

You could also use a ReForm effect to deflect damage. This is an effect we use in game to protect out flag ship from siege weapons.

EDIT: The +2 soak is to someone wearing armor affected with the spell. The armor itself is effectively immune to damage.

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Thanks for spotting Hardness of Adamantine ! It means I wasn't far off with the spell magnitude.

Base 4, +1 for stone, two extra levels of soak +2, touch +1, sun +2, structure +3, +4 levels for "continuous" = magnitude 10, level 49.

Now, if we accept that those two extra levels of soak aren't needed, that makes the enchantment level 39, magnitude 8. As Arthur points out, maybe +1 magnitude to include the wooden roof as well.

That would allow Stephen to create the stone in 2 seasons, taking 5 vis.

Thanks all for the other points. All good stuff!

A couple of follow-up questions.

  • Are those numbers for Stephen's abilities about right for an old, capable mage acting outside his specialism?

  • Is there any reason why he's use a huge stone rather than something smaller?

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Huge stone vs small stone?

Huge stone is harder to steal.

I say this as someone who was a player in Promises, Promises...

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As soon as it takes more than a season, you cannot make it a minor item.

3 seasons & 5 vim vis to open the major magical object + 5 Terram/Herbam vis to invest it. As it is now a major object, you could invest more Vim vis in it for future effects and you can make use of the "effect will expire after 70 years" Arthur proposed, to cut one season off the project.

The theme that this is for an abbey suggests there might be a need for the effect to work in a divine aura. You may want to include a bit of penetration in there to ensure it does...

W

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Crazy idea, but... What about MuTe(He) to make a self-repairing building? No maintenance, no repairs needed... Maybe that counts as "protecting" the building :stuck_out_tongue:

Base 4 for "highly unnatural" change, +1 Touch, +2 from Solar duration, +3 Structure and +1 from the Herbam requisite to end with a base effect of level 35.
Then add +4 for continuous effect and you end with a level 39 enchantment.

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Good point about Penetration in the divine aura. But how much penetration is needed? There's no mention of auras affecting the use of other enchanted items.

Perhaps that's a concern when Stephen does the final installation of the stone in the abbey wall, and he may need some roll to ensure the enchantment is effective. But once it's active, I don't think penetration is needed.

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I added a clarifying edit to my post. That +2 soak would apply to someone "wearing" the affected object, not the object. For a building that would be for anyone using it as cover. The affected object itself is "nearly unbreakable by mundane means". In other words it would take an SG ruling for it to be damaged.

A few other notes on its size and weight. Stone is heavy. While 1.5 tons sounds like a lot, you can actually get much heavier without being overly large. Stone is around 150~180 lbs per cubic foot. Just under a cubic pace is 2~2.4 tons. Something of that weight will be near impossible to steal and extremely hard to loot.

A large stone could be both to make an obvious "focal item" or for concealment. A standing stone that will be the center of social or magical events are going to be large and thus several tons. Meanwhile the stones used in the foundation and structure of many large buildings are pretty darn big and can often weigh a ton or two. This is the weight range I think it is in.

There are two "Huge Hard Stone" invested devices in my collection thread which use a Hardness of Adamantine effect. One on itself and one on the entire building. The smaller one is about 7.5 tons, while the larger is around 12 tons.

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Magi of Hermes p.32 - Vulcan's Favor - CrTe 29 (Base 15, +2 Sun, +1 2/day, +3 environmental trigger: sunrise/sunset)

The minor item does exactly that. Add +3 Structure & + 1 Touch and you have a level 49 magical object effect that keeps a structure in pristine condition. May want to add +1 He for the wood pieces if any.

W

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A possible side benefit of enchanting individual+size over structure is that the enchantment will continue working if the structure stops registering as such under damage

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If it stops registering as a structure, then it would most probably stop registering as an individual...

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Why would you say that? 2 walls left from 4 or a relatively linear pile of rubble are both absolutely individuals but not structures but would probably still benefit from the reinforcement

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Because the rationale is the same for T:Ind as for T:Struct. They both need to maintain a certain level of integrity for the magic to anchor to the essence of the thing.

If you chop a body into pieces, a T:Ind spell can no longer affect all of the pieces. It only works as long as you call say "this is Ted" with certainty. Ted can be missing an arm, or a leg. But as you chop pieces of Ted off, at one point you can no longer say "this is Ted", but rather "these are pieces of Ted".

The same thing applies to a structure. As pieces of the abbey are knocked down, at one point you will change from "this is the abbey" to "those are the remains of the abbey".

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I think the main problem with this argument is that an individual human is a discrete thing, but you can interact with gravel just as easily as a solid block of stone using terram(it talks about this in the island of magicians section of tme). I don't think the original cohesiveness of material is a part of its essential nature