A Pathetic Newbie's Spell Design Question: Targets and Sizes

So I'm trying to invent a spell that is a beefed up version of Wall of Protecting Stone (CrTr 25, Ars.5, p 153). I've read and re-read the Targets and Sizes sidebar on p.113, but I'm having trouble making sense of it. I'm trying to figure out what level of spell it would take to create a circular wall just over 3/4 of a mile in circumference. I've done the math, and that works out to roughly 264 paces in circumference. Assuming a wall 4 paces high and 1 pace thick, that's 1,056 paces. Is this wildly impossible? Would it be far easier to simply cast Wall of Protecting Stone dozens of times (perhaps with a Muto Requisite to merge the segments together)?

Sorry if I've just created a slue of mathefication headaches for the sake of a patently stupid question. :blush:

Well you need a wall almost 11 times as long as the regular spell, so i suggest you drop the length slightly so its 250 paces long instead, then all you need is to add +1 to size adjustment.

Add +2 and you can make it 250 paces long, 10 high and 4 wide.
Add +4 and you can make it 25000 paces long, 10 high and 4 wide. :wink:

Each of those +1s you mention is a +1 magnitude, correct?

yes, always

Um...Have you done the math right?

Isn't a circle 3/4 of a mile in circumference a circle that is 1320 paces in circumference?

Richard Love wrote:

You may be entirely correct. For "pace" I consulted Wikipedia, which gave me a measurement I translated as roughly 5 feet, which is what I used in the above calculations. My apologies if I've completely misinterpreted how long a pace is.

Wall of Protecting Stone seems to imply that it only creates a Plane Jane wall, with no built-in towers, walkways or other structures used to resist sieges. Since Conjuring the Mystic Tower has a +3 for "elaborate design", would adding a +3 be sufficient to to add the above mentioned features to the wall I intend to build?

Thank you for indulging my noobish questions. I love Ars Magica with a passion, but I just don't have a head for game mechanics. :blush:

It may be that your mile is off. 1 mi = 5280 ft. So even with 5-ft paces you'd have 1056 5-ft paces to a mile, so 792 5-ft paces to 3/4 mi. You sure you don't mean 1/4 mi?


Oy vey! You may be right. I'll go through the math again, you can all feel free to point and laugh at my mistakes, so long as you correct them :wink: : The PCs tower is your standard Mystic Tower, and we are trying to throw up a wall around it to give the covenfolk a safe area to plant their own crops. We wanted the circular wall to cover an area 1/4 of a mile in diameter (1320 feet). The circumference of a circle is equal to its diameter multiplied by Pi, so we'll use the following equation: 1,320' x Pi = 4,146.9023'. So 4,146.9023' / 5 = 829.38046 Paces. Which is a metric fuckload more paces that I predicted previously, which logically means that I must now purchase and load and handgun with which to blow out my own brains. Please help me avert this terrible fate by showing me the proper Ars Magica way to achieve my aims! :open_mouth:

Thanks in advance,

If you want to create a castle, just go for "structure" and create a castle version of mystic tower.

Building a castle with magic is extremely easy. Dealing with the LOAD of problems it causes it not so easy. If you were a noble and suddenly you had a castle in your doorstep (less than 30 miles away, so quite a few nobles) you would be extremely upset AND thinking that it is the work of the devil.

And then you have to deal with the quasi-crusade called against you and the fun begins :stuck_out_tongue:


A pace is 3 feet in ArM5. This definition is there, but not in an obvious place.

On page 112, under the Duration of Sun/Ring, ArsM5 says: "A ring must actually be drawn while the spell is being cast....The magus may not move more quickly than ten paces per round (five feet per second) while doing this." To understand this you need to know the length of a round; page 172 says "A single combat round...takes about six seconds." Thus a pace must be 3 feet long.

On page 113, under Targets and Sizes, ArsM5 says: "A base Boundary is the same for all Forms, and is one hundred paces (three hundred feet) in diameter."

On page 121, under Aquam spells, ArsM5 says: "A base Individual for Aquam is a pool of water about five paces (fifteen feet) across"


[size=85]Edited to actually give page ref[/size]

Common mistake, but no.

Target Structure: The spells affects everything within a single structure. (the rest is snipped) p. 113.
If you wish to create a single large object (eg. a castle), you need to use a Target: Individual, with a size modifier and plausibly a few extra magnitudes for making complicated stuff.
This is also why there is a problem with the spell in MoH that creates a tent large enough for 10 people: it has target group and as such should make a number of smaller tents. To match the description, it should have had target: Individual at +1 (or +2) for size.

It's often far easier to cast a small effect (or several sequential effects) rather than try to combine them into one ultimate spell. The difference is speed if they are spells (casting 1 big spell is faster than casting several small ones), or vis-cost if it's a big ritual. (And if you want a permanent wall, you want a Ritual.)

And the "style" factor, but that's a diff discussion. 8)

But this may not be one of those cases, and smaller spells are noticeably less serviceable than the big hammer. (see bottom)

Yes, but one has been corrected before, and recently. :imp:

Sidebar, page 113, states that Creo can only be used with Target:Individual and :Group (and, I'd hope, "Part", tho' that's not stated). Not Structure, not Circle. There are a very few "canon" spells in supplements that break this rule, but it's usually agreed/admitted that they slipped past proof-readers and should be discounted as such. (Ysmv.)

As MS says (and pointed out to me), a pace is 3'/1m in the game. This is never "defined" formally, not in so many words, but the examples are several and clear if one can find them and reverses the simple math.

So, here...

A mile is 1760 yards (paces).
3/4 mile is 1320 (as anyone who ever ran track knows, running 440's or quarter-miles, ahem).
Circumference is Pi x D, or 4147 paces long.
Multiply that by 4 to get height (and 1 pace thick), and you get (accurately) 16,587 cubic paces.

Base 3, 1 cubic pace.
+1 mag = 10, +2 mags = 100, +3 mags = 1000, +4 mags = 10,000 - and here, with luck, your SG invokes The Central Rule (page 111), and calls it good. Base 3 +4 mags = (3+2 = 5, +1 = 10, +1 = 15) Level = 15 + range + duration.

Now, because you asked about the Guidelines on page113, let's build another. Instead of a wall of "solid" and seamless stone, which will appear very magical, let's create an apparently man-made wall of many individual stones.

Base 3, 1 cubic pace
+2 Group, x10.
+1 mag = 100, +2 mags = 1000, +3 mags = 10,000, and done at Level 20 + range + duration.

Note that each individual stone could be larger or smaller than 1 cubic pace.

Note that if you wanted the wall to last a couple weeks, Duration: Moon (+3) and Range:Touch (the minimum feasible) would make these Level 35 and 40, respectively. While having a slightly smaller spell would be easier to invent and cast, it would require casting 10 or 100 (or more?) of them, and moving around the circle to "touch" the next section. Further, if a ritual intended to create a permanent wall, that would be 10x6 vis instead of 1x7 (or 10x7 vs. 1x8 for the "man made" version) - again, clearly a less attractive option.


We must have been playing Legacy Style a lot, then! I have not followed the Creo discussions you mention and was totally oblivious of that. In fact we have quite a few Creo spells that are Ring + Circle spells since.... dunno.... our sagas in the 90's, I think. Structure spells are not used so much, but sometimes they have been used. My players tend to prefer smaller spells (with enough penetration to knock God out of the sky), so it tends to be NPCs performing those spells, so it is 100% mea culpa most of the time :stuck_out_tongue: No biggie in any case, but nice to be pointed out about this mistake :slight_smile:

Time for a review of the spell guidelines, it seems :stuck_out_tongue:


The spell needs to be Group if it creates something that has a lot of components. So, a tent composed of many separate bits (tent poles, canvas, ropes, etc) needs to be Group.

Conjuring the Mystic Tower has a target of Individual, and that creates a tower that is literally made of a single piece of stone. A version of Mystic Tower spell with a Group target would be permissible, and that would be required to create a more conventional tower composed of a lot of stones.

The sidebar Target and Sizes, p 113, says that a target Group can contain as many individuals as desired, with the total mass equal to 10 individuals of the form. It can be one (but that is less efficient that a Target Individual +1 Size), two, ten, or one hundred.
In this case, as Richard Love stated, it's because a tent is composed of independent parts that need to be accounted for separately.

Sorry I just abruptly abandoned this post, there has been much chaos at work this last week (I got a promotion! :smiley: ). I thank you all profusely for your in depth response! It will take me a while to process these replies, but if I can ask one more favor, can you help me put together what we've established in this thread for a Ritual I'm callingRaising the Arcane Oppidum:

This ritual (if this is remotely possible) should create a circular wall, made of a single piece of stone, roughly 10,000 paces long, with built in towers/ramps/other necessary fortifications. If it makes it easier, we could simply cut ritual up into Fifths, so that each casting creates 2,000 feet, but must be cast five times with a Muto requisite (to make them all fit smoothly together).

The base would be 3 + 4 mags (perhaps plus a few more mags for including fortifications?). Cuchulainshound calculated that as coming to Level 15 + range + duration. Like Mystic Tower, I imagine the range would be Touch and the Duration would be Momentary? Does this seem right so far?

Your Worshipful Servant,

Don't worry, happens all the time. (Delays, not the promotion - grats!)

For a Ritual, touch/momentary seems perfect. Any more Duration is completely unnecessary, and any more Range is just flash. 8)

(10,000 paces long?! A pace is a yard/meter - that's 6 miles/10 km of wall, over 2 miles/3 km diameter, more than enough for any but the largest cities! But you know what you want - we'll stick with that figure for now...)

Size tends to be in powers of 10 - 1, 10, 100, 1000, 10,000, etc. So "2000" is the wrong way to go unless 1) the mage can't learn a larger spell, and 2) your SG/troupe decide that 2000 is the same as 1000 (See Central Rule, p 111), so it saves 5 Levels.

There is no point to making it one magnitude (x10!) smaller in size but one magnitude bigger with a Muto Requisite, unless you want to cast each section, move and consider, cast another section, move and consider, and repeat ten times for ten times the vis expenditure. One casting, call it good.

(Edit - Question: Does this break the Hermetic Limit of Arcane Connections, that a maga can't create something where she can't "sense"? This could easily go over the next hill/horizon and into a town or through farmer's home. I'm blanking atm.)

10,000 paces long - and how high and how wide? We need to know the volume of the stone, length x height x width. This is a serious wall, but "x10" would be handy - let's say 2 paces wide and 5 paces long for now. Later, maybe adjust it a little (a LOT?) shorter and a little higher/thicker. 10,000 x 2 x 5 = 100,000 cubic paces.

CrTe Base 3 (1 cubic pace of stone), +1 Touch, +...

+1 mag = 10, +2 mags = 100, +3 mags = 1000, +4 mags = 10,000, +5 mags = +100,000 cubic paces, or Level 25 for a simple wall, 6 miles/10 km long, 5 paces tall, 2 paces thick, nothing fancy. Defined as a straight line or ring or whatever, no adjustment possible (except via Finesse) - not yet...

Now, the ability to make it different shapes, and add the towers/ramps/etc, are both added "complexity", and that has to have final approval by your SG/Troupe for your Saga. But without complexity, you get a simple ring/line/whatever of stone, shaped as defined, cast the same every time (subject to Finesse rolls).

If you want everything custom/adjustable, so each casting is different and appropriate to the land and situation, I'd say use Mystic Tower as a good base, and go with +3 complexity. This would allow a ring or square or curved/angled walls of almost any design, complex and different towers where you want/need them, battlements, passages and rooms within the walls, gateways (gates not included!) - the works!

(I would say that +1 would give "some stairs and an archer's wall on top, OR some wider adjustability of shape, and +2 would give a lot but not truly "custom" - but +2 might be just enough - but not truly "custom" or adaptable.)

Base 3, +1 Touch, +5 size, +3 complex, = CrTe 40*

Nice spell if you can pull it off. :wink:

(Note that if you wanted a WALL, instead of 2x5 (= 10, +1 mag) you could go 7 paces (21') thick and 14 paces (52') tall (7x14 = ~100, +2 mag's), for Level 45.*)

(* And this, again, is subject to the Central Rule - if the SG feels it's too powerful, they can bump it up, or vice versa.)

This is OK, and doesn't break the Limit of Arcane Connections. You don't need to be able to sense/see the whole thing. You just need to be able to sense/see a part of it. So if it's a big thing you may well not be able to see the entire extent of it.

Even a character who creates a standard Mystic Tower, for example, can only see one face of it, and can't see the interior --- and yet the interior, and other side, nonetheless still get created.

It would be rare to be able to see the interior or "far side" of anything created, tower or mouse, and absurd to expect the need to.

I'm worried about the fact that they can't see where it will be created, or at least not all of "where".

Add a couple more magnitudes, turn that 6 mile wall into a 600 mile wall - now whatcha got? :confused: