GURPS and large-scale spellcasting

I've been thinking about how you'd set up magical precautions against natural disasters in GURPS. It seems like exactly the sort of system where you could do that sort of thing. Hurricanes, earthquakes and so on are devastating, so it's reasonable that a benevolent government would pour effort into effective countermeasures. Even an actively malevolent ruler might do so, because the economic impact and infrastructure damage is really inconvenient.

This post examines the case of Seismia, a country prone to various disasters.

One of the troubles is the sheer area natural hazards affect. GURPS generally handles area spells with a fixed cost ("base cost") per radius in yards.* This cost is the amount of Fatigue Points you need to spend (basically, how tiring it is). A meagre half-mile radius with a base cost of 1/2 clocks in at 440 Fatigue Points. That's roughly one noble estate or village.

*they also measure things in miles per hour, degrees Fahrenheit, pounds of weight, feet and inches, making the system an absolute ruddy nightmare for the sort of scientific realism it's meant to support. For those wondering why the game isn't more popular, this is probably a factor. Yes, I know Americans have an abiding love for their imperial measurements (and I use plenty of them myself in everyday life), but they are wildly inconvenient when calculations come in. Put out a metric version, for the love of all that's holy.

I'm not a great judge of typical capabilities in GURPS, but human capabilities hover around the 10 mark; I'd guess an experienced mage would buy up Health and buy extra Fatigue Points, so they might be able to throw in 20FP or so. Far short of our total.

Ceremonial casting might help. This is much slower (one-tenth of normal speed), but that isn't a problem. It allows other mages, and even random bystanders, to contribute some of their own energy. We're still limited, though...

• Each mage who knows the spell at level 15+: as much energy as he wishes to contribute.
• Each non-mage who knows the spell at level 15+: up to 3 points.
• Each mage who knows the spell at level 14 or lower: up to 3 points.
• Each unskilled spectator who supports the casting (by chanting, holding candles, etc.): 1 point, to a maximum of 100 points from all spectators.

"Mages" are those who have the inherent power of Magery, rather than merely having learned a spell; they're better, faster, stronger and more wizardly.

So a 440-point spell to keep rainstorms out of a 1/2-mile radius would require the full exertion of 22 mages who know the spell at a high level. That's a tough order for one village.

If we have all the villagers come along to chant, they can add up to 100 points to our total. Let's say we can find 100 of them. Let's also say our Head Wizard can rustle up extra energy from magic items, contributing 40 points and leaving us a nice simple 300.

To make up the 300 points, we'd need 100 lesser spellcasters - mages who don't know the spell in question, or non-mages who know it very well. Mages are generally in short supply, though. Perhaps Seismian government compels everyone to study certain spells for national defence against hazards, the same way they might require longbow practice?

That 1/2-mile radius is 0.78 square miles, or about 2km². The population density of Scotland is 70/km², so that would give us 140 inhabitants or thereabouts. Conceivably, if all of them had been forced to learn Protection From Hazard at 15+, and we made all of them participate in the ritual alongside our Head Wizard (20 FP), we could get the energy we need: 3 FP x 140 = 420 FP.

Of course, learning those spells requires investment of time and effort. Most spells are Hard skills, and expensive to learn. For those Seismians lucky enough to have average IQ 10, learning the skill at IQ+5 will cost a mighty 24 points. Those down at IQ 8 have to spend 32 points! Considering ordinary folks tend to have 100-150 points in total, that is a very significant investment in one niche skill.

Looking through Thaumatology, not many options help with spellcasting costs. The obvious one is, of course... sacrifices.

Sacrifice

This section of rules is deliberately fluid, giving no specific set of rules, but a set of ideas and discussion of their implications - for example, how the value of a sacrifice is calculated will determine the kind of sacrifices that happen.

Fantasy, however, gives some useable guidelines.

The basic currency of sacrifice is hit points. If the victim is sapient and consents to the sacrifice, use his full HP. If he does not consent, divide his HP by 3. For nonsapient victims, always divide HP by 3; they are presumed not capable of consent. At the GM’s discretion, offerings of material goods worth 20% of a campaign’s starting wealth count as 1 HP. Offered wealth may be cast into the sea, burned at a shrine, ritually consumed by someone possessed by a god or spirit, or otherwise destroyed or made inaccessible... Each HP of sacrifice could be exchanged for two energy points of magic.

According to Low-Tech Companion 3, sheep have 10 HP. They can therefore be sacrificed for the equivalent of 6 FP.

Wales supposedly contains around 1500 sheep per square mile (I resist my inclination to fact-check this in detail). Let's assume this is a reasonable figure for our hypothetical country, and that whatever sheep-equivalents it might farm (potentially including crops) are fungible in terms of density and sacrificial potency.

With a modest 1% tithe of livestock, Seismia can gather 15 sheep per square mile for sacrifice each year annually, providing 90 energy towards spells of various kinds.

Putting it together

We have to make some assumptions about mage density here. Let's say that there is one high-class mage per 10 square miles, able to contribute 20 energy. There are 2 decent wizards per square mile, who can contribute 3 energy. Assorted inhabitants can give us another 100, and we have 90 energy per square mile from sheep.

Putting all that together... we don't have enough. Our half-mile radius can produce 306 energy, far short of the 440 required. To protect the village from storms, we'd need to increase the Seismian sheep-tithe to 4% of livestock, which is a fair chunk considering it'll be on top of other taxes.

It only gets worse when I reveal that the actual cost for protection from storms (Weather Dome) is 3, not 1/2. We'd need 2640 energy to protect the village!

Thankfully, this sort of thing works better at scale. In a 10-mile radius, we have 31 top-flight mages, 628 decent ones, and a 2% sacrifice will net us 9420 sheep. This gives us 59132 energy, more than our target of 52800.

Sticking with Wales as our current example, it's roughly 170 miles from top to bottom, so we need to cover an 85-mile radius. That will cost us 448800 Fatigue Points to bespell against storms. However, we can muster an impressive army of mages: 2270 top-class mages for 20 FP each, and 45396 decent ones giving 3 energy apiece. There's frankly no point getting the ordinary folks involved for a mere 100 energy. We'll make up the difference with sacrifices: a mere 2 sheep per square mile will suffice and to spare.

Of course, we'll probably want to cast some other protective spells on the whole country, so I'd better stick with that 1% tithe. Plus... with ceremonial spellcasting, any roll of 16+ on 3d6 is a failure! We might need to give this a few goes, lads. Still, it's not a bad outcome.

Base FP cost of spell
Radius (Miles)	1/2	1	2	3	4	5	6	7	8	9	10
1/2	440	880	1760	2640	3520	4400	5280	6160	7040	7920	8800
1	880	1760	3520	5280	7040	8800	10560	12320	14080	15840	17600
2	1760	3520	7040	10560	14080	17600	21120	24640	28160	31680	35200
3	2640	5280	10560	15840	21120	26400	31680	36960	42240	47520	52800
4	3520	7040	14080	21120	28160	35200	42240	49280	56320	63360	70400
5	4400	8800	17600	26400	35200	44000	52800	61600	70400	79200	88000
6	5280	10560	21120	31680	42240	52800	63360	73920	84480	95040	105600
7	6160	12320	24640	36960	49280	61600	73920	86240	98560	110880	123200
8	7040	14080	28160	42240	56320	70400	84480	98560	112640	126720	140800
9	7920	15840	31680	47520	63360	79200	95040	110880	126720	142560	158400
10	8800	17600	35200	52800	70400	88000	105600	123200	140800	158400	176000
85	74800	149600	299200	448800	598400	748000	897600	1047200	1196800	1346400	1496000

 

Top mages	OK mages	Sacrifices	Top mage energy	OK mage energy	Others	Sacrifices	Sum	Without sacrifices
1	2	30	20	6	100	180	306	126
1	6	90	20	18	100	540	678	138
1	24	360	24	72	100	2160	2356	196
3	56	840	56	168	100	5040	5364	324
5	100	1500	100	300	100	9000	9500	500
8	156	2340	156	468	100	14040	14764	724
11	226	3390	226	678	100	20340	21344	1004
15	306	4590	306	918	100	27540	28864	1324
20	402	6030	402	1206	100	36180	37888	1708
25	508	7620	508	1524	100	45720	47852	2132
31	628	9420	628	1884	100	56520	59132	2612
2270	45396	45396	45396	136188	100	272376	454060	181684

Have I missed something? If you know of an energy-saving technique that would help Keep Seismia Safe, contact your local Hazard Dispelling Bureau immediately.