Casting From Sanity

[Ninjadeadbeard]

Is there a good rpg model for casting spells using one's Sanity score? I like the idea of magic being fueled by one's soul/sanity, and I'm looking for a system to back me up.

Any system at all would be helpful. Thank you.

[Glimbur]

Arkham Horror does this, but it's a board game so I'm not sure how much help it will be.

[Arbane]

Is there a good rpg model for casting spells using one's Sanity score? I like the idea of magic being fueled by one's soul/sanity, and I'm looking for a system to back me up.

Any system at all would be helpful. Thank you.

Call of Cthulhu (Arkham Horror is based on this (very loosely).) - If you use magic, eventually you go insane and become an NPC. Every spell you cast costs SAN Points, and they don't come back easily. That's what you get for messing with a vastly superior alien race's mathematics-based reality-manipulation technology, monkey-boy.

Conan d20 - Magic causes Corruption checks. Fail too many, you get ugly, evil, crazy, or all of the above.

Black Company d20 - ditto.

Mage: the Ascension - Casting too many spells causes Paradox, which can result in practically any weird thing the GM wants, from you getting sucked into another dimension to obsessive-compulsive disorder

Mage: the Awakening - Overusing magic causes Hubris, which is bad for your Morality Meter. When it goes to zero, you become an NPC.

Unknown Armies - To become able to use magic, you have to be so obsessed with something (like booze, television, sex, books...) that reality itself is forced to wrap itself around your obsession. Just the actions you'll need to take to get and keep the power you need to use your magic (like never sobering up, cutting yourself, never touching soil) will make you seem like a mental case to most people.

There's plenty more where these came from, but I hope this is a good start.

[Edge of Dreams]

Not quite the same thing but...

The Dresden Files RPG uses a system of Stress and Consequences. Stress goes away after each scene, but Consequences last longer depending on how severe they are. There are three types of Stress - Physical, Mental, and Social, and characters with higher stats in the relevant area can endure more stress before taking a Consequence.

Casting spells almost always causes Mental Stress to the caster. Bigger spells cause more Stress, but this can be reduced by having high Mental stats and/or carrying "focus items" - things like a staff, a wand, an amulet, or some other piece of equipment that helps you control your spells. If a caster screws up his spellcasting roll, he might take additional Physical or Mental Stress as backlash from the failed spell.

Thus, it is possible for a spellcaster to cause Mental Consequences to himself due to casting too much or screwing up a spell. These can be anywhere from migraines to hallucinations to going absolutely insane, depending on how far they overstretch themselves.

[Kadzar]

Also, in the Dresden Files RPG, if you break one of the Laws of Magic, you have to take a Lawbreaker stunt. If this drops your refresh rate below zero, you become an NPC. If not, every third time you break that specific Law, your refresh rate will drop by one until you've spent 3 total refresh (although you also get a +1 bonus to breaking that Law every time your refresh rate is dropped, which makes it more tempting to use). Also, every third time one of your Aspects is corrupted into one relating to the Lawbreaking (which happens until you have no more left to turn), basically twisting everything that makes you you into something that reflects on your magical sins, and causing you to be easily Compelled to further acts of Lawbreaking.

[Studoku]

The Sanity variant rules for D&D 3.5 are OGL and include this feature. The rules themselves are mostly cribbed from better sanity related games but I feel I should mention them for completeness:
http://www.d20srd.org/srd/variant/campaigns/sanity.htm

[icefractal]

Mage: the Awakening - Overusing magic causes Hubris, which is bad for your Morality Meter. When it goes to zero, you become an NPC.

Only to a certain extent though. You won't become a paragon of Wisdom if you're throwing magic all over the place, but you won't fall below the middle-range from that alone. It also has Paradox like MtAs, but whether that actually becomes a problem depends on how and when you're using magic - some characters may barely run into it.