Originally posted by Green Knight
In most D&D games, magic is just a neutral force. What I'm wondering is this: Is there a D20 system in which there are CONSEQUENCES for using magic?
The Sovereign Stone system uses a mechanic that causes fortitude saves while casting to avoid temporary hit point damage caused by the physical stress of channeling magical energy through ones body.
For instance, I was watching Buffy, and it's been mentioned that the use of magic always has consequences.
This comes from a common Pagan tradition, sometimes known, among other things, as the threefold or trifold law, which basically says that anything you cause upon another with your magic will be returned upon you three times over.
IMO, this belief doesn't work in a D&D/D20 game unless you have seriously revamped the magic system. Who in their right mind would toss out a 6 dice fireball if they were going to have to take 3 of them in return.
Of course, you could say that the trifold law works metaphorically in your world, which is how I understand it to work in Pagan circles. So, if I cast a 6 dice fireball at someone, I wouldn't literally have an 18 dice fireball handed back to me, but would eventually (such things are not immediate, and will likely happen at the worst possible moment, showing, imo, the Goddess' sense of irony and humor) suffer something just as bad, from my point of view. This could be cool, but the mechanics for it in game seem elusive. I far prefer something like the Sovereign Stone system, which is not as inspired or cool, but a lot more playable.
Also cool is the "test of wizardry" concept, best exemplified in the Dragonlance novels. Basically, before you can become a mage, you have to undergo a series of horrifying and physically ruinous ordeals and tests. After you've passed the test, you can cast magic without consequence, but you've paid a substantial price to get there.
Lastly, you could adopt a system akin to that used in Ravenloft, where the caster must make saving throws (probably willpower in this case) whenever she uses her magic or begin to slide down the path to evil. This works best if you have a set restriction in your game against evil PCs, dooming them to NPCdom if they ever cross the NE or CE threshold, or saying that there is a virtual 10th, irredeemable alignment on the grid, and if a PC slips to that level they are out of play and will serve the DM as a nasty NPC villain. MAKE SURE THE SPELLCASTER'S PLAYERS KNOW THIS AND AGREE IN ADVANCE! It's not likely to be well recieved if you spring it on them in play.
What I would do is require a will save (DC 10 + 2xSpellLevel) every time a spell is cast. For every 3 or 5 failures, the PC slips one step down the ladder (LG to LN to LE to NE to CE to NPC for example).
What you could do to sweeten the pot and give the player a little temptation to inspire them to roleplay their character's temptation better is offer what Ravenloft called "Dark Gifts". As the PC slips down the road to arcane damnation, they could gain a meta-feat everytime their alignment changes. This feat should be chosen by the DM and need not be particularly useful (giving quicken spell to a 2nd level caster for example).
