Spells : trading duration for FP cost ?

[Mavelic]

Hi,
Is there somewhere a rule that manages an exchange of duration against FP ?
For example, a spell that normally lasts 1 hour could last only one minute against a reduction of its cost in FP of 50% ?
I have looked a little in the books I own but it must be present somewhere?

[evileeyore]

Originally Posted by Mavelic

Hi,
Is there somewhere a rule that manages an exchange of duration against FP ?
For example, a spell that normally lasts 1 hour could last only one minute against a reduction of its cost in FP of 50% ?
I have looked a little in the books I own but it must be present somewhere?

There is not, but I would certainly allow it at my table.

However as this is adding flexibility, beware. I'd bake in a penalty and minimum cost (a minimum even after accounting for high skill). By RAW the caster can always set a shorter duration and even simply stop a spell early (but that costs 1 FP).

My suggestion: For every 10% the cost is reduced, the caster takes a -1 penalty, up to a maximum of -90%. Even after accounting for high skill cost reductions the spell always costs a minimum of 10% rounded up.

This keeps ye olde "I cast No Smell of free because I have skill 15 and am only having it last 5 minutes". It also stops ye olde "I cast Stench* for 1 minute with a 10 hex radius for free because I only need it for 1 minute and I have a [high skill]".





* And honestly I suspect it's the 'long' duration Area spells that will see this most applied to.

[Plane]

If we look for Powers penalties as a precedent, "Hard to Use" gives -5% for a -3 penalty to use a skill, so you would need the maximum 4 levels of it (-12) simply to pay for the +20% enhancement "Reduced Fatigue Cost"

If you paid for some of that with "Reduced Duration" you could get the following combinations:

a) 1/6 duration (-15%) and Hard to Use 1 (-5%) giving -3 to skill
b) 1/3 duration (-10%) and Hard to Use 2 (-10%) giving -6 to skill
c) 1/2 duration (-5%) and Hard to Use 3 (-15%) giving -9 to skill

If you didn't want to take a skill penalty then paying for 1 level of RFC would be 1/10 duration -20%

Costing 1 energy per 6 minutes for No Smell doesn't seem too bad, but I understand the concern with "free" spells, since even though there are advantages that cost 0 energy, they usually cost more points to learn than spells do.

In this case though, using this approach to fund the equivalent of RFC2 (+40%) the highest limitation of "Reduced Duration" is 1/60 for -35% so you would still need to take at least 1 level of Hard to Use (-3 to skill) to offset it.

Magic 9 says you don't need to make skill rolls to maintain spells... if you argue that the Hard to Use discount does not apply when you don't have to make rolls, then it could only offset "Reduced Fatigue Cost" on the initial casting (when you make a roll to take the penalty) but it could not offset the cost for maintenance (since you don't roll) meaning you still pay 1 energy per second to maintain, even if you get the first minute for free.

You could give the option of free maintenance but only if they make the initial skill roll each minute to avoid the FP cost.

[Mavelic]

Thanks to both of you for your anwers.
The simple solution given by evileeyore suits me.
I'll use it for some magic items effects with exclusive powerstone not reloadable (once the ps is empty, the item is no more magic).

[ericthered]

There is a system on myGurps* for trading energy for enhancements to spells. I like to recommend it in these circumstances.

*MyGURPS is the website of the assistant line editor for GURPS, mostly written before he became assistant line editor. It has a number of really good house rules and tweaks.

[Plane]

Does it work in reverse, reducing energy for limitations?