Theoretical Spell Crafting #1

Games Discussion Ars Magica
1

So.

Two of my players are having a hard time getting their heads around the magic system when it comes to inventing spells, and I've been trying to show them how you can approach a problem from many different directions. I thought it might be fun to throw this out to the community as an exercise in Magic Theory and see what people come up with.

Similar to Chess or Bridge problems, the goal here isn't to come up with the BEST solution, just the best given the restrictions.

For the first problem:

Your Magus is travelling in Spring and comes to a river. The river is fast moving (about 6 knots) and wide (almost 100 paces). There is a bridge, but unfortunately it has collapsed in the middle leaving a 30 pace gap.
You need to get yourself, your cart, your horse and your grog safely across the river, in a reasonable amount of time (so no waiting while the bridge is rebuilt with manual labour).

What is the lowest level spell (or spells) you would need to accomplish this?

2

for low level probably craft magic rego herbem- rebuild the bridge in a moment.

3

Okay, but how exactly? Show your work.

4

ReHe base 3 - control an amount of wood (the cart) +1 touch range +1 diameter(or concentration) duration +1size (so you can control an amount of wood as big as a cart)

The base guideline of 3 is enough to make wood move violently (like dance of the staves) or fly like Tangle of wood and thorns. So, put you, the grog and the draft animal on the cart, and then cast this level 10 spell to float the cart over the river. This level is at a level where a Rego specialist could spontaneously do it, but enchanting it into the cart with "Item maintains concentration" allows you to have a self-moving cart.

Or - bridge repair CrHe 10 - level 3 base create wood in an unnatural shape, such as a living wall or bridge, +1 touch, +1 diameter duration, +1 size (from 1 pace across to 10 paces across, that's 30 feet )....aargh the bridge this creates is only 1 pace wide so you, the horse and the grog can easily cross the gap in the bridge, but trying to get a cart across something that narrow is virtually impossible unless you add another size magnitude.

To MuHe the half of the bridge you're on so it stretches across the gap, or twists to move you over - MuHe 3, +1 touch, +1 duration, +2 size (I'm assuming 35 paces long , at least 2 paces wide and over a pace high so 100 cubic paces at a minimum) level 15, maybe 20 if it's a particularly or wide bridge.

5

Bridge repair: craft magic using wood from the collapsed bridge to make a more narrow bridge:
prepared wood base:1, dur mom, range touch (+1), target individual, +2 size (from bridge of wood). total level:4

6

I'd be interested in knowing the favored Arts of the characters. Since you're going for the lowest level, it's probably being a spontaneous effect and it would be done in the favored Arts of the characters.

Lowest level is one thing, but it might be out of reach if the effect is spontaneous and the TeFo is too low. Specialists would handle the problems completely differently...

7

Wow! I think level 4 would win this! Where are the rules for "craft magic"?

8

The finesse ease factor would be ridiculously high. The level of the spell is certainly low. But again a specialist would be involved here. I'd estimate that it's 15 or 18 to deconstruct and reconstruct a new bridge from the existing bridge material... Not many magi have Per+Finesse that can reliably get to 15 or 18...

9

Level 20, Bridge of wood. Base 3 +1 touch +2 sun +2 size. Supports creatures up to size +4. Modified from original version in that it's now only 2 paces wide, but a little over 50 paces long.

An alternate variation on it is 1 pace wide, 100 paces long. The bridge remains anchored for the duration sun. Depends on the depth of the river and the width of your cart, TBH.

Perdo ignem on the water, freeze it to ice to cross? Not sure what level you'd regard that base as, but +1 touch, +2 sun. +2 size, as above. I'd guess Base 5 (strongly chill an object, for example, freeze water) though, meaning level 30

Rego aquam. Magical dam. Lasts for duration diameter, probably. +1 touch, +1 diameter, +2 size. Base 4 means level 20.
Alternately, same as the perdo ignem, Base 3 (turn liquid into corresponding solid) for a level 15.

Creo Terram, base 1. +1 diameter/concentration (I'd consider concentration and ride in the cart as the grog drives), +1 touch, +2 size. Total of 5, creates a spit of sand. Let's assume the river is 2 paces deep, with that sort of flow speed it's already kinda nasty at that depth. So we need to fill 100 by 2 by 2 minimum to allow the cart to cross. That needs 400 cubic paces of sand. Base 1 makes 10 cubic paces. * 10 for +1 size, * 10 again for the next +1 size. Makes 1000 cubic paces. This means our 'sand bridge' is 5 paces across, going reasonably, to allow us to cross, while allowing for bits of it will wash away.
Level 15 if you want to create stone instead, since Base 2 and an additional +1 size since stone is base of a single pace.

Rego Herbam. Base 3, as suggested by SilverOak, but use it to ensure the cart doesn't deviate from the path you send it along, then drive it through the river via the magic. No need to care about the flow of the water, the magic is the ONLY thing allowed to move the cart.

10

The problem with ReHe Base 3 control wood I have is that it basically does a better version of Unseen Porter. At the least, it should have the same restrictions as Unseen Porter, such as a maximum height of 6 feet above any ground that is capable of supporting the cart. Depending on the depth of the river...might be a problem.

11

Hence why my version doesn't do that. It uses the same abuse of the magic that there's an example of in the flambeau chapter of Societates :wink: (The gyro-stabilized lance, anyone?)

12

You can do a CrTe 15 and create a stone bridge that last 2 minutes. Might need size +3 so it would be a CrTe20. Base 3 size+2 touch, Diameter.

Pulling a Moses with the River would be a ReAq 15 but could you get the cart through he mud in time?

You could fly the wagon and grog ( and magus) across with ReHe 5 I think. Base 3 size +1 Touch concentration or Diameter. Teleporting the Horse is base 20 so that would get expensive.

It is more expensive to turn the water solid so we can ignore that one.

Easiest would be to patch the bridge yourself with CrHe 15 Base 3 +2 size touch Diameter should do the trick.

13

finesse 12, daily work of semi skilled artist/craftsman is 9, with +3 to extend that to what could be done in a month

14

I think you're being a little cheeky asking for full worked examples, but can't hurt to try.

  • Creo Herbam or Terram, to conjure a new bridge. There is a spell in the core rules for this under CrHe called Bridge of Wood (CrHe20), which would probably need another magnitude to span 100 feet because of size,and you could reduce the Duration down to Diameter. e.g. Final effect is still CrHe20 (Base 3, +1 touch, +1 Diameter, +3 size).
  • Cr He to repair and replace missing parts in the old bridge. Probably the same level as the spell above, but a different effect.
  • ReAq to lift the water in an arc, or move it away from the people as they walk across the river bed. Moses. Spell is around ReAq15. (base 4, +1 touch, +1 Diameter, +1 Part). this affects part of the river around the magus, affecting fast water.
  • CrAu to create a wind to blow the targets around.
  • Or ReCo to move yourself, then the grog, then ReHe for the cart, then ReAn for the horse. I guess you'll need around level 20 for each effect, maybe 15.
  • Or ... try a knowledge AreaLore check for alternative crossing point. Sometimes a magic screwdriver isn't the best choice. You find a place where the river is thinner and you need lesser power spells, or a ford, or bridge (how are the normal people in the area dealing with not having the bridge?).
  • InAq XX, find a point where the river is not 100 paces wide.
  • Craft magic, as stated above, but that will require a fair finesse level which might make the bridge dodgy without the caster knowing.

It depends on the caster's arts.

so Q. What is the lowest level spell (or spells) you would need to accomplish this?
A. ReAq15

15

I think it's more than what one skilled craftsman can do... Building a bridge doesn't happen by only one person...

16

Plus another 3. Using Finesse instead of a Craft skill is always +3 what a mundane Craftsman could do, so Finesse 15 is the target. This is the tradeoff with Craft skills; they tend to be lower-level spells than simply conjuring up a raw product whole, but they're trickier to do well.

17

Terram Guidelines: "For sand, dirt, mud, clay, or similar substances, it is about ten cubic paces of stuff."

Just fill the intervening space with clay. Enough clay will be solid enough to get across the gap if you don't tarry.
Base 1, +2 Size (for 1000 cubic paces of clay), +1 Touch, +1 Diameter = CrTe 5

Or if you're worried about timing, make it Sun duration:
Base 1, +2 Size, +1 Touch, +2 Sun = CrTe 10

This can be created as a massive block 30 paces long (the length of the gap) x 4 paces wide (should be enough for the cart) x 8 paces high (which is plenty of height) = 960 cubic paces across

Worried about the current? Create several blocks to form a chevron to create a water brake and divert it away from where you plan on putting the "bridge" of clay.

Just as an exercise, how heavy would this be? Dry clay has a density of 100 lbs/ft3. So 960 cubic paces = 25,920 cubic feet x 100 lbs/cubic foot = 2,592,000 pounds, or 1296 tons of clay. I think it'll hold.

18

Yes, but if you more loosely define one skilled craftsman can do in a month as 30 man-days of work, that doesn't sound too bad.

19

I still doubt that it only takes 30 man-days to build a bridge that spans a river 300' wide.

20

From Covenants, the lowest ReHe craft magic is Base3. It also involves thousands of pieces of wood, so it's a Group Target. That puts it at Base3, +1M Touch, +0M Momentary, +2M Group, +1M Size (at a minimum) = ReHe15. As others have mentioned, the Finesse target on this is difficult. Building a bridge across 100 yards of fast-flowing river is going to be a Hard (Target 12) task, +3 for Craft Magic, and probably something that would take at least a season to do for another +6. That's Target 21, AND you've got a -3 penalty on your Finesse roll for lack of familiarity (from Societas, you'd need Craft: Carpenter 1 to have a +0 on the roll).

Most solutions to this problem really depend on how much a stickler your Storyguide is for 'realism' with regards to things like bridge supports and the like. For example, if Bridge of Wood has supports all along its length, this CrHe20 spell can be cast repeatedly to cross without further issue. However, if it's a free-span supported only at the ends, there's nothing for the Bridge of Wood to attach to (10 yards too short) and it would collapse.

A ReAq spell to move water and selectively freeze it would do for a makeshift bridge. Base3 (freeze water is base3), +2M Voice, +0M Momentary (the ice will melt naturally), +1M Part. That's ReAq10, though probably insufficient to create a bridge without multiple castings (1767 cubic feet of ice per casting). This would only make ice bridges and avoids +1M Flexibility as a result. I'd suggest +2M Size (ReAq20) on general principles.