Magical sensitivity as a double-edged sword?

[Amaril]

So here's a game design question. Let's imagine a magic system where spells are less about throwing fireballs and summoning demons to eat people's faces, and more about subtle things--predicting the future, reading thoughts, talking to ghosts, blessing and cursing people, stuff like that. Now, let's say that in this game, one of the core character stats specifically represents sensitivity to magic; even for non-spellcasters, a high score in this stat would represent things like being able to perceive spirits, or having premonitions about future events, without actively trying. The catch, however, is that the more sensitive you are to magic, the more easily you can be affected by it, and vice versa. So, someone with a high magic stat would be more likely to notice the angry ghost that's hovering around the party ready to cause mayhem, but if an enemy spellcaster wanted to read their thoughts, they'd be an open book, while someone with a low magic stat would give up little or nothing. A low magic stat may also have other effects that are less obviously beneficial or problematic--for example, maybe your magic stat affects how well divination works on you, so a fortune teller could predict every detail of a magic-sensitive customer's future, while that of someone with a low score would be a blank slate. Maybe it actually means their destiny isn't set, or maybe it just makes it unclear--either could be interesting.

What do you think of this idea? Are there games like this? How would you handle it? With these kinds of benefits and downsides, would you allow players in this game to freely set their character's magic score to whatever they want, or would you still make them spend resources to increase it?

[5a Violista]

I think it's a great idea for a story and setting, and it may work for a game. I like it.
I don't know enough about games to give an analysis of what parts of it will work and which parts won't work, or what needs to be taken especial care of.

Also, I don't know if there's already a game like this, but there's definitely a webcomic where this is a general assumption of the setting (Solstoria). Each person is born with an inherent closeness to magic; people with high affinity to it are able to manipulate magic and exorcise spirits, but are also more "delicious" to spirits. The main character, on the other hand, is a "Zero Grade" with absolutely no personal affinity to magic: this makes her less affected by magic, it makes her seem worthless to spirits who want to eat humans (but more useful as a guard or soldier), and it allows her to automatically pierce through any illusion (which, actually, makes her more able to see spirits compared to someone with high magic-affinity, because spirits use magic to hide, rather than use magic to be seen).

So, I would make it so someone with low magic affinity would be more able to notice the angry ghost, but the person with high magic affinity would be more able to do something about it. I would then make this magic affinity stat inherent to character generation: there would be clear pros and cons to having a high or a low (or even medium) stat in it. I would also make it so it can't be changed after character generation, and treat it simply as an affinity to magic (and there would be other stats, such as ATTACK or MIND or whatever that govern magic power and damage, and the magic affinity would either be a multiplier or some sort of tiered list ["If your tier is 1-3, you get a +X bonus on Magic Resist checks vs this spell and any magic you cast has only half its effect; if your tier is 7-9, your spells are 10% more effective but you get a -2 to resisting magic" and so on or something like that])

[Ninjaxenomorph]

Rolemaster actually has a similar system to this. Races that are more attuned to a certain type of magic have lesser resistance to that realm of magic. On the other hand, having a high casting stat also ups your resistance, so spellcasters usually have good resistance.

In a pathfinder setting I work on, one race has an alternate trait that makes all spells cast on them more effective, offensive or not.

[Frozen_Feet]

I use a similar idea for my setting: ability to see & interact with ghosts makes it that much easier for spirits to see & interact with you. Mediums are hence more vulnerable to possession than clueless normal people.

For a non-medium, acting in the spirit realm requires trance or death-like states, which has its own hurdles.

In general, there's a difference between passive and active sensing. Passive sensing is alike to seeing in the dark - you only see those things which produce light on their own. This means there's lot you don't see, but others don't see you either. Active sensing is like shining a flashlight through the dark - now you see lot of hidden things, but now they also see you.

[Lord Torath]

The heroine of the Cast in Shadows books (by Michelle Sagara West) has marks on her body that let her do things no one else can (heal people, wake dragon skeletons, flay child traffickers alive), but also bestow a sensitivity to magic that generates pain in relative level to the power of the magic being used around her. The more powerful the spell, the "hotter" her marks "burn", inflicting no damage to her, but nearly incapacitating her from the pain. You could apply a -1/-5 penalty to all actions depending on the power of the magic being used in the character's vicinity.

[Necroticplague]

NWoD gives you bonuses to casting spells based on the main 'casting stat' in the game, Gnosis.The penalties for magic, Paradox, also get bonuses from high Gnosis . Thus, having high Gnosis means you can cast stronger spells (or the spells you can cast are stronger, or some combination thereof), but have a chance of getting more severe penalties when your casting blows up in your face. It also has it on another level, where higher Arcanum dots (your skill at using that specific type of magic) give you a bonus for casting using that type of magic,but call for stronger types of that penalty within the category (i.e, getting a 'summon malevolent creature' with magic you can barely use summons something minor, like an annoying poltergeist. Getting the same result with a magic you're a veritable master at summons something that is incredibly powerful.)

It also had 'being able to cast magic makes you're soul a bit more resistance to being ripped out, eaten or damaged. On the other hand, all the kinds of creatures that would do so would love to do so to you, and it's fairly obvious to magical senses.

[thedanster7000]

GURPS magic resistance works something like that; it's harder to be attacked by spells, but also harder to cast or be magically healed.