Ok, I know the simple answer is "enough to make it fun" So I'm posting this to put some order in my thoughts, see how many blind spots you can find in this system, if it's definetly broken or missing something important. Oh, and excuse my english, it's not my bitrh language.

Setting of the game: players roleplay present day young magicians, discovering the ways of classic magicks
Magic system: players get their characters spend resources (mana, hit points, materials, etc) to cast spells. Player rolls dice to hit, target rolls to avoid/resist if applicable.
Problem: generating an spell list with an appropiate "mana cost" for each spell.
My approach to the problem: instead of making up every spell myself or using a list from another game, I prefer to identify all variables spells can have, assign a cost to each one according on how much the result will affect the game and then either randomize for a list or let players create their own spells.

Variables I've got so far, listed with possibilities from the cheapest to the more expensive in terms of cost:

COMMON VARIABLES
-effect: damage, improving movement distance, improving damage, improving defense, static ilusion, continuous damage (like fire or poison),  suggestion/charming, additional attacks, additional targets, summoning creatures with normal attacks and movement, damage ignores armor, flight, partial paralysis, mobile illusion, invisibility, summoning creatures with any of these effects, teleport, suffocate.
-range: touch, short range, long range, area.
-duration: instantaneous, amount of turns. (I prefer not to include "permanent" here, it makes things too complicated for the setting)

LIMITATIONS (these reduce the cost of the spell)
-amount of timas a day (1-3)
-components: material, vocal, somatic, focus
-magic school: divine, demonic, necromancy, elemental, druidic, alchemy (sure, we can keep adding. Feel free to mention any other you find fun and simple to play.)
-type of damage: no damage, contundent, slashing, penetrating, cold, heat, electric,

counterspelling can be done by paying the same cost needed to cast the spell. Hmmm, I've got the feeling i'm missing something important here...

Ars magica does this.  It makes magic feel like science.  Is that the feel youre going for?

See if you can dig up a copy of "Chill" from Mayfair games in the mid 1990s.

It has a great magic system that could be a great source of inspiration.

It uses a series of contributing factors that build up points (spend HP, resources, make skill checks, have assistants, perform magic at the right places/times, etc.), and a series of basic component outputs that can be constructed together into a spell (then yiu add points for range, duration, area of effect, potential saving throws, etc.)

It was one of the most flexible and interesting magic systems I'd ever seen until Mage:the Ascension came out.

stefoid wrote:
Ars magica does this.  It makes magic feel like science.  Is that the feel youre going for?

It may also be worth giving the Hero system a look.  Uses an effects-based system, which it looks like you are trying to do.

The trick is to make a scientific system (which it will have to be in the back-end) look and feel mysterious.  Will the players know it is
a mathematically created system?  Maybe, but so long as the characters don't (meaning that the spell mechanic hides the effects-based
math well enough) then all is good.

In other words, the way magic really works does not have to be written into the rules.  Dice don't lie, but they can sure hide the truth.

--AMG

Ok, this is what I've got so far:

[URL=http://img217.imageshack.us/i/spellcosts.jpg/][IMG]http://img217.imageshack.us/img217/1815/spellcosts.jpg[/img][/URL]

Uploaded with [URL=http://imageshack.us]ImageShack.us[/URL]

No matter how many limitations a spell has, it's cost can never be under 3 points of mana. PCs start with barely 10 points of mana, though they can find items that store mana for personal use. And they can also use elemental magic for free, though the power and precision are defined by the dice roll only. I'm not using characteristics at all for this game, so dice rolls and some resource management make up for most of the system.

I found the old version of The Chill, the magic system available to players I found there was quite limited by the setting. Perhaps Elements of Magic would be more helpful, but then again, I think I got it all almost solved with this. I removed all mind-controlling effects since they make the rest of the effects pale in terms of results and thus affect the narrative flow and control quite seriously. I'm still doubtful of teleport, even with the cost listed there. Perhaps it should be replaced with "Portal". Feel free to question my judgement though, and if you've got any more ideas for either effects not listed or limitations, please let me hear them. Many thanks!

Those descriptions make it sound like a science report.  If you are going for mysterious, arcane magic, why not replace them with something more or less equivalent, but more colorful?  even something completely abstract that more or less means the same thing?

Maybe make it karma based. E.g., do something merciful, or loving or healing or creating something that makes people smile or laugh, and a mage gains +karma.  While conversely, harming, killing, destroying, takes from your karma bank. And if it goes over, it takes points off the mage's life. That might also allow you to reduce the number scale down to something more manageable, based on the type of spell. Maybe a 1 thru 10 point scale for (+) and (-) karma?

Hi there,

Please provide a link to any kind of external document regarding your game. That's a requirement for using this forum. If you have any questions about it, check out the sticky thread leading this forum, or ask me through private message. But until the link's available, everyone, no more posting to this thread, please.

Best, Ron