Help making Powers and Threshold Magic work together
 

At the prompting of the magic user in my group I've started looking at Threshold Magic.

I think I understand how it works, but how is the threshold to activate the spell determined?

I don't particularly like standard magic and would prefer to use Powers as Magic to make them. How would determining the spell threshold be handled?

Finally how does the Mana Level of the setting affect the system?

I may have completely missed the answers to these but I haven't found them either in book or on the forum.

Any help is greatly appreciated.

Re: Help making Powers and Threshold Magic work together
 

The threshold needed to activate a spell is the same as the FP cost to cast. So a spell that costs 3 FP will add three to Tally. So adding 1 Tally would presumably be a -5% limitation (although it's probably worth -10%; that first cost makes a huge difference in how people use the ability).

Mana works just as normal. -5 in Low Mana, requires Talent in normal mana, does not require Talent in high mana, and infinite Threshold reduction in Very High Mana.

Re: Help making Powers and Threshold Magic work together
 

You need to distinguish between "Threshold" and "Tally".

Tally is the currency you pay to cast the spell. It is determined exactly the same as for the standard magic system (area costs, reductions for skill, etc.) but you don't pay it with fatigue points. You just add it to your accumulating Tally.

Threshold is the Tally score at which you start hitting problems. When your Tally exceeds your Threshold, make a Calamity Check. If you add to your Tally while it is over your Threshold, or you cast or maintain a spell while over your Threshold (even if they cost zero) you also make a Calamity Check. You only have to make one calamity check per event.

A magician has a natural recovery rate for Tally, which will bring them back below their Threshold, eventually. The suggested default numbers are recovery 8 and Threshold 30, and there are advantages and disadvantages to modify both figures.

Re: Help making Powers and Threshold Magic work together
 

The normal energy cost to cast or maintain a spell is applied to the tally (Thaumotology p 76). When tally accumulates to be more than the threshold, a calamity might occur (Thaum p 77).

Mana level effects Threshold magic normally: magic cannot be cast in a no-mana zone, spells are at -5 to cast in a low magic zone, people without Magery can cast spells in a high mana zone, and tally is refunded on a successful cast in a very high mana zone but all failures are critical failures. By default, mana levels do not adjust tally, Threshold, or Recovery Rate.

If you're creating magic as powers, then use Nuisance Effect: adds 1 tally (-5%) in place of Costs 1 Fatigue (-5%). It's up to you how much tally any particular spell incurs.

As always when using Threshold magic, I advise dramatically increasing the Recovery Rate (ideally above Threshold) and making the Calamity table less painful on the low end and incapable of affecting things other than the caster on the high end. The reasons being that Recovery Rate, not Threshold, determines how many spells a mage can cast per day, and 8 energy of spells per day is pathetically low. Having the Recovery Rate higher than Threshold encourages players to go over Threshold and actually engaging with the Calamity table, which is also helped by less painful calamities on the low end. On the high end, a mage shouldn't be able to turn himself into a suicide bomber by casting a ridiculously large spell, and limiting large calamities prevents that.

The last two threshold mage PCs in my games had Threshold 30, Recovery 45. One of them managed to trip 5-6 calamities before needing to stop spell casting for a week. I think his penalties at that point were double tally costs for 2 of his favorite spells, double tally casts for both of those spells' colleges, and a reduced Threshold and Recovery. It was quite exciting watching him push his luck well past the point of reason.

Re: Help making Powers and Threshold Magic work together
 

Thank you. Sorry about getting the terms mixed up. I've been cramming the subject the last couple of days, and it shows. I think I can defiantly modify the Powers (I'm an electronic pack rat. Have files dating back to the days of floppy disks) so I can find my build notes.

Re: Help making Powers and Threshold Magic work together
 

That's how much they can cast per day, every day. I've always thought of Threshold Magic as being something where the characters will frequently get close to or past their Theshold, but then will avoid casting for several days to recover. 8/30 should work for "weekend adventurers*," where they can use a decent amount of energy over the weekend but then need to avoid any magic through the work week. But for characters where adventuring/magic is their day job, I agree a recovery rate of 8/day seems entirely too low.

*Which, given all the bits about Jobs, Cost of Living, the 80/20 split of Wealth, etc, feels like sometimes that's the assumed default for GURPS.

EDIT: As for the effects of mana level on Powers, first off the Magical -10% Power Modifier automatically makes mana level important, so that's got you covered there. For abilities that have an activation roll, you're looking at -5 in Low Mana; you might be able to justify +2 in High Mana and +5 in Very High Mana, but I'd advise against it. For abilities that don't have an activation roll, I'd be inclined to just make them less effective in Low Mana - half damage, +3 to resist, half duration, etc, although you could also just make them unreliable, with a 50% or so chance to fail to activate. If using more fine-tuned mana levels, such that Low Mana can range from -9 to -1 (-10 is No Mana, +0 is Normal Mana), replace that -50% with 10% multiplied by the penalty - in -3 Mana, things are 30% less effective (so 70% as effective as normal), last 30% less time, or have a 30% chance of failing to activate. I'd probably let the character spend more energy to help overcome this, probably double energy to overcome -5/-50%.

Re: Help making Powers and Threshold Magic work together
 

If you're trying to combine magic as powers and threshold magic together, the simplest thing to do is to substitute "Tally" for "FP" anywhere it shows up.



Now, most of the time, magic as powers doesn't use FP. The exception is if you are using the options from powers chapter 4 (its hard to get to that part of the powers book if reading strait through, but its really good). The big examples are Extra Effort (page 160) and stunts (starting on page 170).



This will result in small powers that can be used a lot and then every so often they can be massively boosted.



If you want every spell to have a high FP cost, its really hard to do that via raw in a way that feels right. I've used 1 FP gives a [5] point discount to a maximum of 4/5th's of cost before, and it feels right to me, but that's completely my house rule, and I haven't played a serious game with it. Tally should be able to use that as well.



I hope these two suggestions help

Re: Help making Powers and Threshold Magic work together
 

Also, look at GURPS Horror. There's a section in there about “Power Corrupts” (pp. 146–148) that specifically addresses this, talking about how various systems of “delayed cost” exist in GURPS: Black Magic/Spiritual Assistance, Meditative Magic's “point debt” in GURPS Fantasy… and Threshold-Limited Magic; and it suggests “Corruption” and a general term for what these “benefits now; costs later” systems track. While it's written in the context of “making supernatural powers inherently evil”, that's something that can be reskinned.

It then goes on to talk about how these systems can be repurposed to apply to supernatural powers other than magic, such as Enthrallment or Imbuement skills, Effect-Shaping Ritual Path Magic, and Powers. In particular, for Powers it suggests applying the Corrupting Limitation, which in simplest terms causes the ability to generate a point of Corruption with each use for every point that the Ability's point cost is reduced: technically it's a –20% Limitation; but in practice, start by deciding how many points it reduces the Ability's cost by and reverse-engineer the percent discount from that. Relabel that from “Corruption” to “Tally”, and you're set.

And there's also the suggestion of converting the energy costs of things like Temporary Enhancements and Trading Fatigue for Effect into Tally buildup. I'd also add “Using Abilities at Default” to that list.

Re: Help making Powers and Threshold Magic work together
 

I'd need to look back through Horror (and Thaumatology for that matter), but I'm pretty certain Corruption is a lot worse than Threshold. IIRC, Corruption doesn't really go away on its own, you need to basically perform good deeds or receive absolution from a higher power or something similar to erase it. Also, instead of getting too much of it risking a (minor at first) Calamity, getting too much automatically results in you basically losing character points in the form of gaining appropriate Disadvantages. I think using Costs FP's -5% for each +1 to Tally is going to be more appropriate than Corruption -20% (in fact, I think -5% for +1 Tally is probably more appropriate than -5% for Costs FP really is).

Re: Help making Powers and Threshold Magic work together
 

Following the section which I cited, there's an example Corruption system, which is not definitive; it's just one way that Corruption can be implemented. Using Black Magic as a basis for Corruption is equally valid, as are using Assisting Spirits or Threshold-Limited Magic — though if your intent is to use it to represent the “power corrupts” idea, you should probably tailor the Calamity Table in much the same way that Thaumatology has tailored Critical Fail tables to represent different flavors of magic. But while the section is couched in the concept of magic being inherently evil, the concepts presented in that section are less about that and more about matching systems of “paying the price later” with systems for representing non-human abilities other than magic. I would know: the section that I'm referencing is almost verbatim text that I submitted during the GURPS Horror playtest.

The Corrupting Limitation was proposed by another playtester, whose main motivation seemed to be that he didn't like how “Costs FP” adjusts the cost of the ability proportional to the Ability's cost, but doesn't adjust the FP cost in the same way. That's why the discount if Corrupting is only nominally –20%, and is in practice proportional to the number of Corruption points generated. It wasn't about “Corruption is harsher than FP, so it should be worth more as a discount”.

The Sample Corruption System came from a third playtester, who wanted there to be suggestions for how to gain Corruption other than power use. It also provided its own guidelines for the price you pay for gaining Corruption and the means you use to get rid of it, essentially defining another system that parallels Black Magic, Spirit Assistance, Threshold-Limited Magic, and Point Debt. In fact, it parallels Point Debt in much the same way that Black Magic parallels Spirit Assistance.