Skill Based Magic System

[Centaur]

I'm thinking of designing a purely skill based system of casting spells. The idea is that the character builds up ranks in "Magic Paths" that allow him to achive certain effects based on what is possible with that path.

example paths could include: Elemental paths (eg. Fire, Cold, etc.), Positive Energy, Negative Energy, Matter, Life etc...

depending on what the charcter wanted to achive, he would add up the DC modifiers from several different catagries to achive a final DC. He then makes a D20 roll + skill and either succedes and achives the desired effect or missed and losses the spell energy. Realy bad misses, more than 10 say, could also create some sort of back lash.

Modifers could be for example with the fire path:
-Desired amount of damage
-Desired number of targets or area of effect
-Desired range or distance to target
-Spending mana points reduces DC
-Material components reduce DC
-etc.

Any thoughts on how you would do something like this.

 

[steveroe]

Ars Magica has a skill based magic system that might give you some good ideas. It was co-written by Jonathan Tweet, of PHB etc. fame.

It has several skills that divided spells into effect and target. Creo (Create) and Ignem (Fire) would be used to cast spells that created fire, etc. Casting spells required skill checks to determine their effectiveness.

I don't remember how limits on spells/day were handled. Adding skill checks or saves to use up daily power points or mana might help rebalance the spell casting classes.