Skill based rules for Elements of Magic ?

[gpetruc]

while still waiting for the revised Elements of Magic to come out, an idea came to my mind:
I have always tried to design a skill based magic system for D&D but the main problem was a good free system to create spells. But now Elements of Magic provides this, and so I only need a way to convert from magic points to skill checks:

If you remember Ars Magica (a great free system, but it would be a headache to port it to d20 well), you can see that Elements of Magic provides everything we need, that is:
- two axes for creating a spell: choose the verb (evoke, compel) and the object (water, humanoid, ...)
- a very good flexibility, with about 15 verbs and 40 objects.
- a precise way to determine the cost/power effect of spells (MPs)
- there is already a way of combining spells together, even if it requires them to have the same verb (transform water and air ...)

Is anybody interested in the project ?
If someone is I could try to post the first drafts of the system.

Thanks

 

[RangerWickett]

I'm interested.

 

[Phaedrus]

I'm interested.

Will it be an exclusive/training-only skill? Or can anyone perform skill-based magic?

 

[RangerWickett]

Well, we have a few hurdles here. I'm not familiar with Ars Magica, so I can't compare, but I know some issues that may cause problems since we're doing D20.

How much do we keep of the current system? We need to determine what scales, and what sets limits. Since we want skills to affect how well we cast spells, we need something else to limit how powerful we can get.

Now, EOM already has magical skills, so we can use them as a baseline, perhaps. The magical skills are there because the effects are too powerful, such that a single spell list was not a big enough price (Divination is really useful!), or because it seems a natural extrapolation from an existing skill (Spellcraft = detect magic), and because its thematically kinda cool to have some spells be skills (counterspelling things is sort of the antithesis of normal casting).

In the current rules, your caster level limits how much MP you can spend on a certain spell. Now, in a skill-based system, would we still use MP, or would you just have to succeed a skill check to cast your spell. I can see a couple options here:

1. No MP is needed, just a skill check, but the MP Cost of the spell you try to cast cannot exceed your caster level.

2. MP is needed, and so is a skill check, but there is no limit to how much MP the spell costs. Thus, a 1st level mage could try to cast a 5 MP spell. He'd most likely fail, but he could always try.

3. Make a skill check before you decide what you cast. The skill check determines your MP limit for this spell, so if you want to cast a meteor swarm but you roll poorly, you might get stuck casting a fireball instead.

 

[gpetruc]

I'm glad to see that there is someone interested (and the RangerWicket himself, what a honor)

Now some more of my ideas:

To cast a spell no MP is needed, you choose the spell and make the necessary skill checks to cast the spells.
There is, anyway, the limit that the maximum MP-equivalent of a spell is skill ranks-3 (or 2 ranks for 0-level spells), mostly to avoid trying luck too much.
Also, the reason behind the rank limit was that if you cast a "Transform Water 5/Air 7/Fire 2/Earth 1/Void 0/Life 0/Time 0" you don't want to make checks for all the elements but only the more important ones (Water, Air). without the rank limit you could in this way cast that spell without having a single rank in any of the skills for the minor elements.

Spell skills would be purchased with a separate set of skill points (or 1 rank could cost a small fraction of a skill point) so that you can have a good number of spell skills but you can't, let's say, trade just the spell Lava skill with a much more broad standard skill like Spellcraft or Spot.

Skill checks would be done in the following way: one check for the verb, and one for each maior element/creature/... and possibly add a DC modifier for the flavour components.
The maior components are the ones that, summing up their MPs, are more than 4x (or 3x, it's all to tweak) the toal MP cost of the remaining components.

Example:
Evoke Fire 5/Earth 3/Lightning 1/Air 1/Void 0/Gen 4 would require:
1) a Evoke chech (with a DC for the total 14 MPs) (maybe +3 DC for the three flavour components)
2) A Fire check (DC for a component of 5 MP)
3) A Earth check (DC for a component of 3 MP)

note: Ars Magica just adds up the modifiers and roll a single check, but this seems a bit out of the d20 scheme.
Also, they don't have the feature of using more than one element in a spell while for us is important (but we don't want, for example, to have that if you are good in casting Space then Evoke Fire 7/Space 1 is easier than Evoke Fire 7, and so adding modifiers does not work).

Make a skill check before you decide what you cast. The skill check determines your MP limit for this spell, so if you want to cast a meteor swarm but you roll poorly, you might get stuck casting a fireball instead.

This is a good idea (and is a bit like how it works in Ars Magica: you determine the level of the spell with the check, and then pick effects allowed for that level), even if it could make the rules a bit more tricky.

Also, there is the problem that you can't have penalties for failure, which should help balancing out the fact that without MPs mages can go on casting all day long:
My original scheme was:
- if you fail a check you take 1 weariness point.
- each weariness point gives you a -2 (or -1?) to spellcasting checks.
- resting 10 minutes removes a weariness point
(and, optionally, something like)
- a big failure (let's say by 5+, or 10+) gives you a load of weariness (let's say 4 points), and you become exhausted (or fall unconscious ?)
- If the weariness points are greater than your Con modifier, you are fatigued

In this way you can't just go on trying for a difficult spell, and even trying once could be risky as it could live you without spellcasting for a while if you fail badly the check; instead, you can go on casting simple spells as much as you like, which seems fine.

 

[netnomad]

You guys may want to check Mongoose's Chaos Mage or Sovereign Stone's Codex Mysterium. They are both skill based magic systems.

-NetNomad

 

[Phaedrus]

I think one skill check (either before you choose what to cast or after) is better than a bunch (one for element, one for verb, etc.). It speeds play and seems more elegant.

Perhaps multi-element or multi-component spells have a DC modifier? A fire-only spell is much easier to weave than a fire laced with void spell. A single target spell is easier to weave than a multi-target spell. And so on. But even here I think the goal should be to keep things as simple as possible.

 

[RangerWickett]

One minor thing; I know you don't have the full rules available yet, but you can't include a 0-MP use of a spell list if there's more than one spell list being used.

F'rinstance, you can cast Evoke Ice 0/Gen 4 to get a nice, long-range ice spell that does 1d6 ice damage. You cannot have Evoke Ice 0/Evoke Death 0/Gen 4 and try to deal 1d6 each of ice and cold damage. You'd have to go Evoke Ice 1/Evoke Death 1/Gen 4, in which case the spell would deal its normal base of 1d6 (for an evoke spell) plus 2d6 more (for the 2 extra MP).

 

[gpetruc]

One minor thing; I know you don't have the full rules available yet, but you can't include a 0-MP use of a spell list if there's more than one spell list being used.

Ok, this is fine, it makes things simpler: in this way the flavour components must have a MP cost and so we don't need to balance them out with a DC modifier.

I think one skill check (either before you choose what to cast or after) is better than a bunch (one for element, one for verb, etc.). It speeds play and seems more elegant.

Me too knows that a single check is better ... but what check ?

Suppose the spell is Evoke Fire 4/Space 2/Void 1/Gen 6
1) How can I pack in a single DC the fact ? DC = (13 MP DC) + (DC modif for having 3 components) ?
2) And, expecially, what modifier do I have to use for the check ? I need that the check must depend heavily on my Evoke skill, the fire skill should be important, the space one less important and void skill is nearly irrelevant...
- I can't just use the Evoke modifier
- I can't just add up (or average, maybe it's better) the skill modifiers of Evoke, Fire and Space

Note that having to look in many tables to get the correct DC and skill check modifiers to cast the spell and adding them up could result in being longer than simply rolling two or tree dices. (All the basic spells Verb + Object + flavour will need only two checks, that you can easily roll simultaneously if you have dices of different colours; and the maximum dices needed will be 4 or 5, but we might set it even as low as 3)

One positive side-effect of multiple dices is that you get a bell curve, that makes casting "safer" as it is easier to predict what you could cast and what not.

Anyway, it anyone has a simple and elegant way of reducing it to a simple and elegant single skill check please tell it.

 

[gpetruc]

First Draft !!

I've made the first draft of the rules, and I'm posting it here for comments.

I've attached the cleanly formatted RTF file (6.5 Kb, zipped), but I'm writing it here in vB code also (without the table, but with the formula to get the table values)

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Rules in brief
Spells: the spells used in these rules are a generalization of EoM spells; the only difference, anyway is that you can use more than one verb in the same spell. All spells can be seen as a combination of more simple spells, that are as the spells in EoM.
Spell skills: for each verb and object there is a spell skill; ranks in spell skills are bought using a separate set of skill points. The number of ranks in a skill restrict the maximum MPs you can use in that component.
Spellcasting: to cast a spell a character simply needs to have meet the minimum ranks needed for the MPs used, and then roll skill checks; simple spells will require two checks, while very complex ones, using many different verbs and objects could require more (all the skill checks are independent, so they can be rolled all together to save time if you have dices of different colours)
Weariness: failure in spellcasting results in acquiring weariness points, that result in penalties to casting checks until they are healed by resting. Much weariness could also make a character fatigued, exhausted or even unconscious.
Definitions and concepts
Before staring with the hard rules we will introduce the terms that will be used, and provide some general concepts. Note that most of this is really trivial to understand.
Duality: objects and verbs are interchangeable in the rules, their role is completely symmetric.
Simple spells: a simple spell is either a verb applied to a list of objects, plus optionally a general part, or viceversa (by duality) an object followed by a list of verbs and optionally a general part.
Examples: Evoke Air 4/Void 2/Gen 1; Air Move 2/Transform 4/Gen 3.
Complex spells: complex spells are a sequence of simple spells; they will be discussed later
Total power: the total power of a simple spell is the sum of all MPs.
Example: in Evoke Air 4/Void 2/Gen 1 the total power is 7.
Base of a simple spell: the base of a simple spell with a single verb is the verb, while the base of a simple spell with a single object is the object. If a spell has a single object and a single verb, the caster chooses which one is the base. The spell is considered to have a power equal to the total power in the base object or verb.
Example 1: in Evoke Air 4/Void 2/Gen 1 the base is Evoke, with power 7.
Example 2: in Air Move 2/Transform 4/Gen 3 the base is Air with power 9.
Example 3: in Infuse Life 3/Gen 2 the base can either be Infuse or Life, with power 5.
Components of a simple spell: the components of a simple spells are other things that are not the base and the Gen part. Their power is equal to the MPs spent for them.
Example 1: in Evoke Air 4/Void 2/Gen 1 the components are Air (power 4) and Void (power 2)
Example 2: in Infuse Life 3/Gen 2 if Infuse is chosen as base then Life is the component (with power 3), while if Life is the base Infuse is the component (again with power 3).
Note: from example 2 you can understand that choosing the base makes difference, as the DCs are based on the power, and are different between bases and components.
Primary components and flavour: sort the components of a simple spell and pick the ones with greater power until the sum of the powers of the ones you picked is three times or more the power of each of the remaining components; the components you picked are the primary components, and the rest is flavour. In case of components with equal power the caster chooses between them. A spell never has more than three primary components.
Example 1: in Evoke Air 4/Void 2/Gen :1 both Air and Void are primary components
Example 2: in Evoke Air 6/Void 2: only Air is primary (6 >= 3*2)
Example 3: in Evoke Air 4/Void 2/Force 1: Air and Void (4+2 >= 3*1)
Example 4: in Evoke Air 4/Void 2/Force 2: Air and ether Force or Void (4+2 >= 3*2)
Example 5: in Evoke Air 4/Void 4/Force 4/Time 2/Space 1: Air, Force and Void
Example 6: in Evoke Air 4/Void 4/Force 4/Time 4/Space 4: any three
Note: it might seem complex at first, but is really trivial.
The Rules
Spell Skills
Spell skill points: The number of spell skill points a mage gets every level is equal to 10 + Int. modifier; at first level the points are multiplied by four as usual. Humans don’t get bonus spell skill points.
Spell skills: there is one spell skill for each verb and object in EoM. All spell skills are class skills for the mages, but there might be specialized classes or prestige classes that have some spell skills as cross class. The maximum ranks in a spell skill is equal to your caster level + 3.
Minimum ranks: to cast a spell with a power X in a verb or object you need to have at least X+3 ranks in the corresponding skill; for power 0 spells only two ranks are required.
Note: this is because you don’t make a check for each component, but nevertheless even for flavour components some knowledge must be required, and this seems the simpler way to do that.
Casting simple spells:
Casting a spell requires a check for the base and one for each of the primary components.
Base check: the base check DC is taken from Table 1, using the total power of the spell.
Component check: the DC is taken from Table 1, using only the power in that component.
Table 1: base DC
Values in the table (a first draft) are: base DC = power + 12; component DC = power + 8
Weariness
Acquiring: Any failure by 5 or more in casting a spell results in acquiring one point of weariness.
Effects: Each point of weariness gives a −2 penalty to all spell skill checks.
Recovering: 10 minutes of rest, or one hour of light activity such as walking or eating, allow you to heal a weariness point.
Catastrophic failure: if a casting check is failed by more than 10 you automatically gain 5 weariness points.
Other effects (optional): 3 weariness points make you fatigued, 5 make you exhausted and with 7 or more you fall unconscious.