Long time without posting :P ok, after several tests I came up with another ruleset to try on a medieval fantasy game. I'm still using the Anima rpg setting so characters are all human, but the rest is pretty much classic D&D alike.

However I've been struggling to find or design a versatile magic system that doesn't depend on a huge and detailed spell list which for the taste of my group of players can be practical but eliminates all the mystery and exploration they could roleplay on it otherwise. So lately I've been playing with an idea based on the laws of magic by Isaac Bonewits http://www.neopagan.net/AT_Laws.html So far I've got:

-Every magician character define their own kind of magic according to three laws (not exactly all Bonewits establishes but based on those) and rolls for his WILL stat to cast a spell.
-The target makes an opposed roll to avoid the effect BUT if it fails his WILL score adds to the spell empowering it. Every witness convinced of the power of the magician also adds power to the spell in the same way, either if it's friend or foe.
-But also the magician can fall for this. Let's say a Necromancer cast a spell on a paladin. The paladin also his a magic of his own, only he calls it "Faith" so the WILL roll is gonna be more difficult to pull this time and if he fails his magic is gonna become weaker against the paladin.
-Of course, magic is invisible unless the magician uses some trick to empower his act. The effects however can be quite real for the target and witnesses

So magician characters grow stronger by buying, finding or making items that increase their confidence in their power, or help them convince other people of it. Thus a magician in this game actually needs a party, minions or believers of some sort to perform the most powerful spells, otherwise they are as useful as the Rincewind character of Terry Prattchet books.

I'm hoping this can help balance magic users with pure fighters in the game. Fighters will have a similar system but that is for another post. So now to the questions:

-I'm sure this concept isn't new. Does anybody has experience with a magic system like this? Any pros and cons of using this system that come up to your mind will be really useful.

-Any ideas of what the figther would need to get balance against such magicians? I've got a few of my own but I would like to hear your opinions first.

Many thanks for your time!

Ok, shorter version:

FREEFORM MAGIC SYSTEM, and by that I mean completely. Bring your own idea of magic to the table, works (almost) exactly as you wish and all your character's gotta do is convince other characters their powers are real. This should empower roleplaying and the EXPLORATION into the magic world.

Just to keep it around a theme, you define your way of doing magic using three laws. It's powered by your WILL stat and adds the will stat of those who believe in you. Cleric, anyone? Of course, your characters believes in himself, or should at least most of the time.

QUESTIONS:

-Anybody played with a system like this? Went good, terrible? why?

-based on this i want to design a FREEFORM COMBAT SYSTEM, any ideas?

So far I spotted one problem: on his turn the mage wil make everybody roll to see if they get to add their will score to the spell. I'll guess it will be quicker to make the mage roll to get the attention of the target and other combatants and plain add that roll to his spell. If anybody tries to help him by spending their actions, fine, they get to add their roll to the spell if they do it right. If anybody tries to interrupt the cast or make a counterspell or simply try disbelief, that's fine too.

Last night talking with players brought another couple of things to the table: fighters need to be focused to fight properly, almost as much as mages need to concentrate on their spells. So NOW bards are useful. But instead of letting players manage that I'm gonna add an npc bard that helps the side that pays him most, either by buffing up the characters or making the enemy lose focus. All magic in this system has become a battle of will now, and that kinda have interesting side effects...