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Old 01-24-2015, 11:10 AM   #1
Qhaysh
 
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Default [RPM] Adapting Ars Magica into GURPS

Ars Magica is a great game: it has a wonderful system for spellcasting and spell-design, and the setting is interesting and quite well-written. The problem is that the rest of the system is kind of low-resolution. So, being the GURPS fundamentalist that I am, I decided I'd try to convert the AM's magic.

Now, I know we already have Verb-Noun magic in Thaumatology. And although it is interesting, I don't quite find it robust enough (I did take a couple of ideas from it, though).

What I currently have in mind is kind of a mix of both systems (RPM and V/N Magic), but using the Effect Shaping variant (from Ghostdancer's lovely Pyramid Article).

Without further ado, here are the basic concepts:


Skills - Besides the usual 10 path skills (also called Forms, to follow Ars nomenclature) casters will also use 5 other skills called Techniques* (again, following Ars nomenclature).
In this system the 10 Forms are the thing being manipulated, and therefore work very much like the Nouns in the V/N Syntactic Magic from Thaumatology. The 5 Techniques are how the caster manipulates a given Form, and therefore work very much like the Verbs in the V/N Syntactic Magic from Thaumatology.

Casting - All spells involve at least two skills: one Technique (Verb) and one Form (Noun). When casting a given spell, the magus rolls both skills and adds the two margins together (if one of them is a failure, the margin might be negative). The combined margin must be equal to or higher than the final energy cost of the spell divided by 10 (using Ghostdancer's numbers from the Effect Shaping variant)**.
Casting time is calculated as per the guidelines in Effect Shaping.

*Despite the name, these are IQ/VH SKILLS, they are not techniques in the GURPS sense. Ars Magica calls its nouns Forms and its verbs Techniques.
** My rationale for this was that a point in MoS is more or less the same as a -1 penalty in the skill roll. I could be wrong.



I welcome any and all feedback you might have, oh Great Hivemind!
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Old 01-24-2015, 11:47 AM   #2
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Default Re: [RPM] Adapting Ars Magica into GURPS

Can you provide an example like Fireball? I suppose it would be Rego Ignem or maybe Creo + rego ignem (but I am not an expert in AM)

Would magery add to both rolls? How much would it cost in terms of energy and time?

By the way, maybe you can find this link useful http://spellswiki.wikidot.com

It is a fan made grimorie for AM
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Old 01-24-2015, 12:22 PM   #3
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Default Re: [RPM] Adapting Ars Magica into GURPS

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Originally Posted by lvalero View Post
Can you provide an example like Fireball? I suppose it would be Rego Ignem or maybe Creo + rego ignem (but I am not an expert in AM)
It's just CrIg in RAW ArM (looking at Ball of Abysmal Flame and Pilum of Fire).

Now here's an example: Blastius McBlastimus bani Flambeau wants to cast a single-target highly damaging fireball to damage his enemies. Blastius knows Creo (the create verb) at 14 and Ignem (the fire noun) at 18 (the guy loves fire!)

Now a sample fireball spell might be something like this:

FIREBALL
Spell Effects: Greater Create Energy.
Inherent Modifiers: Damage, External Burning.
Greater Effects: 1 (x3).
This spell conjures a ball of flame that the caster can then throw at a target. It does 9d burning damage.
Typical Casting: Greater Create Energy (6) + Damage, External Burning 3d (+8). 42 energy (14x3).

Since the final energy cost is 42, the required combined MoS would be 5 (42/10, rounded up). Now Blastius is casting his fireball. First he rolls against Creo: he gets a 15. Failure! He accumulates -1 "point" for his MoS. Then he rolls against Ignem (his strong score) and gets a 7 (lucky!), gettiing him a net MoS of 10 (11-1). The spell is successfully cast!

It took him 10 seconds to cast this spell. Had he wanted to cast it more quickly, he'd have had to take a -1 penalty for each second "shed".

Quote:
Originally Posted by lvalero View Post
Would magery add to both rolls? How much would it cost in terms of energy and time?
Stupid as that may sound, I had not thought about what to do with the magery bonus. Since in Ars there's no difference in raw talent from one mage to another, I don't think I'd even allow magery.

In terms of energy there's no actual cost, (just like the Effect Shaping variant for RPM). There's just this MoS you have to reach in order to successfully cast the spell.

Time is defined by how many Greater Effects there are in your spell (again, as per the Effect Shaping variant from Pyramid #66), the more of them, the longer it takes to cast the spell. Casting time can be reduced if the caster accepts penalties to his rolls (or maybe if an increase to the target MoS).

Quote:
Originally Posted by lvalero View Post
By the way, maybe you can find this link useful http://spellswiki.wikidot.com

It is a fan made grimorie for AM
Thanks!
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Old 01-24-2015, 12:47 PM   #4
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Default Re: [RPM] Adapting Ars Magica into GURPS

I am not very familiar with RPM but sounds it is a cool way to approach to AM.

With this system you may as well roll 6d against Form+technique. Another option is to roll 3d against the average of form and technique. With this second alternative the MoS should be Final cost / 20 instead of / 10.

Have you considered to have techniques as skills and have forms as advantages like Magery (ignem)? This way you could roll against technique + form in a very natural way.

By the way, in example you sent I think I would rule that the mage needs to be succesful with both rolls to prevent over-specialization
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Old 01-24-2015, 12:51 PM   #5
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Default Re: [RPM] Adapting Ars Magica into GURPS

Quote:
Originally Posted by lvalero View Post
With this system you may as well roll 6d against Form+technique.
Not a good idea. The sum of 6d is far more tightly grouped around 21 than the sum of 3d is around 10.5. I've seen a group make the corresponding mistake in adapting AM to a different game system, and they became ludicrously powerful very fast.
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Old 01-24-2015, 01:00 PM   #6
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Default Re: [RPM] Adapting Ars Magica into GURPS

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Not a good idea. The sum of 6d is far more tightly grouped around 21 than the sum of 3d is around 10.5. I've seen a group make the corresponding mistake in adapting AM to a different game system, and they became ludicrously powerful very fast.
I agree with you that 6d have a very different distribution but in the example provided I think that the final impact over two 3d rolls against two skills adding up both MoS seems mathematically equals as adding the two skills on advance and then rolling the six dice. I may be wrong as I have not make the equations to prove it :)
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Old 01-24-2015, 02:38 PM   #7
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Default Re: [RPM] Adapting Ars Magica into GURPS

Ivalero is right. Consider the following, where

F = Form skill
T = Technique skill
X = The result of a single 3d6 roll
Y = The result of a different 3d6 roll
Z = The result of rolling 6d6

and understand that

(X+Y) = Z, because rolling six dice together is no different than rolling three dice twice and summing it

Given the above, your system adds the margin from two rolls, so:

MOS = (F - X) + (T - Y)

MOS = F - X + T - Y

MOS = F + T - X - Y

MOS = (F + T) - (X + Y)

MOS = (F + T) - Z

See, Qhaysh, what you're missing is that you are rolling 6d6 for this spellcasting -- you're just doing it in two batches, but it's still effectively "one roll" because you're summing the margins.
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Old 01-24-2015, 03:09 PM   #8
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Default Re: [RPM] Adapting Ars Magica into GURPS

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See, Qhaysh, what you're missing is that you are rolling 6d6 for this spellcasting -- you're just doing it in two batches, but it's still effectively "one roll" because you're summing the margins.
Hurrr durrrr! This is what I get for not looking at the math when I come up with something in my head. What would be a good fix for this, then? Splitting the penalty?
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Old 01-24-2015, 05:05 PM   #9
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Default Re: [RPM] Adapting Ars Magica into GURPS

Now, yet another possibility I considered was to have the Technique Skills as part of a calculated base, kind of like an attribute which you buy up or down from 10. I just wouldn't know how to price it... Either 10/lvl or 5/lvl.

Using the previous example, let's say Blastius has his Ignem (Fire) skill at +3. He would then add this relative level to a calculated base (as per Thaumatology p. 31, 32). In this case the calculated base would be (IQ+Creo)/2. Let's say he has Creo at 12 and that his IQ is 14, so his base for all Creo spells is 13. We now combine this with his relative level, and get to a nice 16 for his spell. Since the spell is -5, he would now be rolling against 11.

Does this make any sense? I can never tell if my explanations are clear... :/
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Old 01-25-2015, 01:13 AM   #10
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Default Re: [RPM] Adapting Ars Magica into GURPS

Another possibility is that you could rule that technique is a Talent with levels.

This way you could say that if you dont have a minimum of, lets say, Talent Creo 4 then you cant create simple life. Or that the max time your creations lasts is your level of Talent Creo in minutes. It is a simple way to put hard limits on effects based on the talent.

In this approach the Talent technique is very simmilar as Magery (one collegue only) so the cost could be the same. You may also use Capping syntactic magic rule on Page 184 thaumatology

Another benefit is that for some very complicated spells you could rule that a minimun of a second or third talent is needed at a certain level.
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