Shadow Magic
 

I came up with an idea for magic - it works better in the shade. In broad daylight, skill is at -10. For each -1 to Vision due to darkness, the penalty decreases by 1, so at -3 to Vision you cast at -7, etc. down to total darkness when there is no penalty. What size limitation would this be?

Re: Shadow Magic
 

I'd be inclined to use the same -20% as Night Only. This has the benefit that it works in the daytime - at -10, or better if you can use it in the dark during the day - but the drawback that, even at night, it's only at full skill in pitch darkness. On the other hand, the inverse version where you suffer a penalty to cast equal to the current darkness penalty would certainly not be worth a full -20%, and I'd eyeball it at -10%. With that in mind, I think I'd revise my earlier suggestion and make it -30%, basically having it deviate from Night Only the same amount as "Bright Magic" deviates from Day Only, but in the opposite direction because darkness is less convenient than light (even for a character who has no difficulty operating in pitch darkness, it's easier to make light in a dark area than to make darkness in a bright one by mundane means - and the general prohibition against Magic Enhancing Magic would mean magical light/darkness should generally have no influence).

Re: Shadow Magic
 

Do you mean the penalty to casts depends on what Darkness YOU PERSONALLY are in when you roll the dice? A spellcaster of this magic can retreat to a sealed underground vault during the to cast without Penalty?

Re: Shadow Magic
 

The penalty depends on the darkness surrounding the caster. If he sits in his basement, he can cast spells without a penalty. I don't think I would give more than -20% to -30% at most. It's a less extreme version of Dark-Aspected (which is worth -50%).

Re: Shadow Magic
 

Are you familiar with GURPS Powers? It has the Nature power modifier, with gives -1 per 2 TL of equipment you're carrying, wearing, or riding, or -1 per 1 TL of implants. That part comes to -10%. Since you're allowing -1 per one level of illumination above total darkness, I might accept -20%.

Would you apply greater penalties than -10 for brighter illumination?

Re: Shadow Magic
 

Yeah, I was inspired by Nature's Strength.

More than -10? Yeah, sure. Or just make it impossible. I think -10 is GURPS code for "impossible" anyway (although we all know of characters who laugh at -10).

Re: Shadow Magic
 

This is a cool idea, especially for DF style mages.

I'd call it a -20% to -40% modifier, given that you only have a reasonable chance of casting spells in near darkness, which kills your chances of using combat spells without some offsetting spell or vision-related advantage.

OTOH, if you can offset penalties with tricks like carrying around a parasol or using an enchanted item to cast Darkness on your own hex, the limitation value goes way down.

FWIW, there's a RAW Darkness-Aspected Magery limitation worth -50% which prevents you from casting any spells in conditions brighter than candlelight.

Re: Shadow Magic
 

This one pretty much has to have the rule that magic can't be used to enhance magic. Otherwise, the first spell any mage learns is Darkness, and a Darkness item is probably a standard graduation gift from an apprentice's master.

In this case, the GM can just throw magobabble at it: "Sunlight disrupts the flow of mana through the etheric field that permeates all things. Magical darkness stops the sunlight, sure enough, but beating it back means effective magical darkness has to get the mana flow to resonate exactly out of phase with the sunlight-induced effect, which is just as bad for the coherence of other structured spells."

Re: Shadow Magic
 

Hmm.. shadow or darkness? Would be entertaining if complete darkness was as much of a problem as brilliant light...

Re: Shadow Magic
 

Then you can have a three-way struggle between the Brights, Darks, and Dapplemages.