Roleplayer #18, February 1990
The Compleat Powerstone
Powerstone Enchantment in GURPS Magic
by Brett Slocum
Powerstones are the most common magical tool of the mage. They provide
extra energy for spellcasting, so spells can be cast with less fatigue.
This article will discuss powerstone economics, provide a fast method for
generating large powerstones, and discuss powerstone quirks or warps, those
annoying and delightful little eccentricities powerstones develop during
the enchantment process.
Powerstone Economics
In the production of powerstones, several economic factors are involved.
As stated in GURPS
Magic, the chances of destroying the powerstone increase
as the number of castings goes up. The tables in GURPS Magic
reflect this chance; the retail price given accounts for the average number
of gems lost in the enchantment process. Enchanting any individual powerstone
may destroy more or less gems, but the price remains the same since the
difference will average out.
There is another factor that is not taken into effect in the table in
GURPS Magic: powerstones with quirks. For powerstones of five
or fewer points, the chances of a warped casting are pretty small, so the
market expects these powerstones to be quirk-free. If one with a quirk is
for sale, it will be at a discount, perhaps 25% off. If more than one quirk
is present, greater discounts are given. These are essentially rejects.
The minimum price is probably the total cost of producing the flawed gem,
generally 50% of the retail price.
As the chances of defects rise, though, the expectations of the buying public
change. Larger powerstones are expected to have quirks, and so those without
them are sold at a premium price, which can be determined by dividing the
cost by the likelihood of producing a powerstone with no quirks.
The following table provides exact details of the costs and prices of various
sizes of powerstone. This chart uses the following formulae and assumptions:
Gem Cost is found as per GURPS Magic (p. M20):
$10 x P^2 +$40 x P.
Number of Gems needed: 1/(0.9815^P ).
Labor Cost: average number of castings needed x $25.
Total Cost: (Gem Cost x Number of Gems) + Labor Cost.
Retail Price uses a markup of 100% over the Total Cost.
Zero-Quirk Probability: 0.9717^P.
Zero-Quirk Price: Retail Price / Zero-Quirk Probability.
Listed Price is the price from GURPS Magic (p.
M20).
Prices have been rounded to convenient values. Costs have not been rounded.
Powerstone Cost Chart
........Gem....Num. ...Labor....Total.....Retail..0-Quirk.....0-Quirk.....Listed
Size....Cost...Gems.....Cost.....Cost......Price...Prob. .......Price......Price
1.........50...1.02......25.......76........150...0.9717.........160........150
2........120...1.04......52......176........350...0.9442.........375........300
3........210...1.06......78......300........600...0.9175.........650........500
4........320...1.08.....105......450........900...0.8915.......1,000........900
5........450...1.10.....133......627......1,250...0.8663.......1,500......1,200
6........600...1.12.....162......833......1,600...0.8418.......2,000......1,600
7........770...1.14.....191....1,069......2,100...0.8179.......2,700......2,000
8........960...1.16.....221....1,335......2,650...0.7948.......3,400......2,500
9......1,170...1.18.....251....1,635......3,250...0.7723.......4,200......3,100
10.....1,400...1.21.....282....1,970......4,000...0.7505.......5,500......4,000
12.....1,920...1.25.....346....2,749......5,500...0.7086.......7,500......5,500
15.....2,850...1.32.....448....4,221......8,500...0.6501......13,000......8,200
20.....4,800...1.45.....632....7,609.....15,000...0.5632......27,500.....15,000
25.....7,250...1.60.....837...12,406.....25,000...0.4879......52,000.....24,000
30....10,200...1.75...1,063...18,935.....37,500...0.4226......90,000.....40,000
35....13,650...1.92...1,313...27,573.....55,000...0.3661.....150,000.....58,000
40....17,600...2.11...1,589...38,764.....78,000...0.3172 ....250,000.....80,000
45....22,050...2.32...1,892...53,030....106,000...0.2748.....400,000....110,000
50....27,000...2.55...2,226...70,979....145,000...0.2380.....600,000....150,000
60....38,400...3.07...2,994..120,875....240,000...0.1786...1,400,000....250,000
70....51,800...3.70...3,915..195,617....400,000...0.1340...3,000,000....500,000
80....67,200...4.46...5,014..304,829....600,000...0.1006...6,000,000....850,000
90....84,600...5.38...6,323..461,352..1,000,000...0.0755..12,000,000..1,200,000
100..104,000...6.48...7,874..682,228..1,400,000...0.0567..25,000,000..2,000,000
This table also simplifies the generation of powerstones
that are not fully enchanted up to the capacity of the gem. Take the Gem
Cost of the carat size of the stone, multiply by the Number of Gems for
the number of enchantments, add the labor Cost for the enchantments and
multiply by two for the Retail Price. To determine the price of further
enchantments, subtract this price from the price for a fully-enchanted powerstone
of the proper size. Though this price seems too high, the enchanter assumes
the risk of destroying the gem, instead the owner of the powerstone. If
the enchanter destroys the gem, he will replace the powerstone. If the owner
wants to pay just for the enchantment, use the labor cost of the difference
in power of the powerstone.
For example, if a PC wants to buy a ten-carat powerstone with only five
powerstone enchantments on it, get the Gem Cost of the carat size of the
stone ($1,400), multiply by the Number of Gems for a five-point powerstone
(1.1), add the labor Cost for the enchantments ($67) and multiply by two
for the Retail Price (a total of $3,214, which probably gets rounded to
$3,200). He now can have the other enchantments done later when he can afford
them. To fully enchant this powerstone, subtract this price from the price
for a ten-point powerstone ($4,000). So, the cost of adding the additional
five enchantments is $800. If the PC were very miserly, he could pay $67,
but if the enchanter destroyed the gem, the PC would have to replace it.
Quick Powerstone Generation
Keeping track of the more than 50 rolls needed to create a 50-point powerstone
can be quite tedious. The table at right will greatly speed the generation
of large powerstones. To use this table, find the power of the desired powerstone
in the first column and use that row of numbers. The first column is the
survival roll; if you roll this number or less, the powerstone survived
all castings. If you fail this roll, the stone is destroyed and you must
keep rolling until you succeed. Keep track of how many stones it took to
succeed and multiply by the Gem Cost for the size of gem you are enchanting.
The number of spell castings performed before the gem was destroyed is determined
by the failed survival roll. The higher the roll, the sooner the gem was
destroyed in the process. If a 17 or 18 is roll, the gem was destroyed on
the first casting. If a lower number was rolled, check the survival numbers
for the smaller stones; this will indicate how many castings had been successful
before failure. If more than one power level has the same survival roll,
pick randomly between the choices.
Once you have a powerstone that survived, roll once to find the number of
Quirks that the powerstone has; if the number you roll is equal to or less
than the number in the chart, the column shows how many Quirks were introduced
in the process of enchanting the powerstone. The number pairs, such as 18/xx,
are for when you roll an 18; roll again and compare to the second number
of the pair. Find the column in which the second number is greater than
or equal to the number you rolled.
Powerstone Quirk Probability Chart
.....Surv.______________________ Number of Quirks _____________________________
Size.Roll.0...1.....2......3......4......5......6......7......8......9......10.....11
1....16...15..18....--.....--.....--.....--.....--.....--.....--.....--.....--.....--
2....15...14.18/18.18/18...--.....--.....--.....--.....--.....--.....--.....--.....--
3....15...14..17....18.....--.....--.....--.....--.....--.....--.....--.....--.....--
4....14...13..17...18/16..18/18...--.....--.....--.....--.....--.....--.....--.....--
5....14...13..17...18/15..18/18...--.....--.....--.....--.....--.....--.....--.....--
6....14...13..16...18/14..18/18...--.....--.....--.....--.....--.....--.....--.....--
7....13...12..16...18/13..18/18...--.....--.....--.....--.....--.....--.....--.....--
8....13...12..16...18/12..18/18...--.....--.....--.....--.....--.....--.....--.....--
9....13...12..15...18/12..18/15..18/18...--.....--.....--.....--.....--.....--.....--
10...13...12..15...18/11..18/15..18/18...--.....--.....--.....--.....--.....--.....--
12...12...11..15...18/7...18/15..18/18...--.....--.....--.....--.....--.....--.....--
15...12...11..15....17....18/14..18/18...--.....--.....--.....--.....--.....--.....--
20...11...10..13....16.....17....18/15..18/18...--.....--.....--.....--.....--.....--
25...11...10..13....15.....17....18/14..18/16..18/18...--.....--.....--.....--.....--
30...10....9..12....14.....17....18/12..18/15..18/18...--.....--.....--.....--.....--
35...10....9..12....14.....16....18/10..18/14..18/18...--.....--.....--.....--.....--
40...10....8..11....13.....15.....17....18/13..18/16..18/18...--.....--.....--.....--
45....9....8..11....13.....15.....17....18/12..18/15..18/18...--.....--.....--.....--
50....9....8..11....13.....15.....17....18/10..18/14..18/16..18/18...--.....--.....--
60....8....7..10....12.....14.....16.....17....18/12..18/15..18/18...--.....--.....--
70....8....6...9....11.....14.....16.....17....18/11..18/13..18/16..18/18...--.....--
80....8....6...9....11.....13.....15.....16.....17....18/11..18/14..18/16..18/18...--
90....7....5...8....10.....12.....14.....16.....17....18/9...18/13..18/15..18/18...--
100...7....5...7.....9.....11.....13.....15.....16.....17....18/11..18/14..18/16.18/18
For example, the GM wants to create a 50-point powerstone.
First he rolls for survival, needing a 9 or less: he rolls 11, 13, and 7.
Therefore, he destroyed two gems before completing the 50 enchantments on
the third, so the cost of gems was 3 x $27,000 or $81,000. The first roll
of 11 indicates that either 20 or 25 rolls had been completed before failure;
the roll of 13 shows from 7 to 10 enchantments had been made. The GM determines
that 25 and 9 castings had been performed on the first two gems for a total
of 84 enchantments. Two powerstone enchanters working eight hours per day
casting four Powerstone spells (one hour of spellcasting and one hour of
rest per enchantment) would take 21 days to complete this stone.
Now, he rolls once to see how many quirks were introduced into the powerstone;
he rolls a 9, which is greater than the 8 in the '0' column and less than
the 11 in the '1' column, so the powerstone has one quirk. The GM decides
that this powerstone cannot be used during the day of the full moon and
one day on either side of the full moon, approximately 10% of the time.
Quirk Determination
The range of possible quirks is only limited by the creativity and sadism
of the GM, but coming up with interesting quirks can be difficult on the
spur of the moment. Essentially, powerstone quirks fall into five categories:
limits on the use of the powerstone, limits on recharging, effects to the
powerstone, effects to the user and other miscellaneous effects and limits.
Use Limits restrict when a powerstone can be used, who can use
it, what actions must be performed before use, what spells or colleges it
can be used for, or other restrictions. Some examples of this type of quirk
are: Only Usable on Wednesdays, Won't Work for Hat-Wearers, Only Works on
Fire Spells and Only Usable Underwater.
Recharge Limits constrain what conditions the powerstone can recharge.
These conditions may be related to time, environment or other factors. Possible
recharge limits include Won't Recharge in Sunlight, Only Recharges in Bat
Blood or Won't Recharge in Tredroy.
Powerstone Effects are abnormalities in the appearance, odor, sound
or other qualities of the powerstone. Some possible effects are Belches
When Used, Smells Like Dead Fish, Looks Like a Ham Sandwich or Repellent
to Elves.
User Effects are strange things that happen to the user of the
powerstone. Some examples are Makes User Thirsty After Use, Renders User
Mute For One Hour, Causes Greed After Use or Stains User's Skin Black.
Any quirk that affects the use or recharging of a powerstone less than 10%
of the time or that has little effect on game mechanics (e.g., Smells Like
Fish) is minor. A moderate quirk causes a small reaction penalty or affects
usage or recharging less than 33% of the time. A quirk that affects the
powerstone 33% to 85% of the time or that has major effects on game mechanics
is major. Severe quirks affect the powerstone more than 85% of the time
or affect the user. These are basic guidelines; individual quirks that fit
one category by these guidelines may belong elsewhere because of the bizarreness
or harmlessness of the quirk.
For example, here are the quirks given in GURPS Magic,
plus others, and possible classifications for them:
Minor: Smells Like Fish (Powerstone Effect), Not Usable by Hat-wearers
(Usage Limit) or Makes User Thirsty After Use (User Effect).
Moderate: Only Charges in Bat Blood (Recharge Limit), Shrieks When
Used (Powerstone Effect) or Very Attractive to Frogs (Powerstone Effect).
Major: Won't Recharge in Sunlight (Recharge Limit), Only Usable
on Wednesdays (borderline severe) (Usage Limit) or Won't Work During Leap
Year (Usage Limit) (even though this is only 25% of the time, the length
of time is all at once)
Severe: Renders User Mute for One Hour (User Effect), Only Usable
for Fire Spells (Usage Limit) or Only Usable by Green-eyed Virgins (Usage
Limit).
Random Quirks
The following rules can be used for randomly determining some qualities
of powerstone quirks. Roll 3 dice:
Quirk Type
3-8 Use Limit
9-10 Recharge Limit
11-12 Powerstone Effect
13-15 User Effect
16-18 Other Misc. Effect or Limit
Quirk Severity
3-10 Minor Quirk
11-13 Moderate Quirk
14-16 Major Quirk
17-18 Severe Quirk
Or alternatively, make a second Powerstone spell roll to find the severity:
on success make it a minor quirk, on failure make it moderate or major quirk
and on critical failure make it a severe one. Treat a 16 as a failure, even
if skill exceeds 16.
An interesting way to create quirks is to open a dictionary or thesaurus
at random and blindly point to a word. Either use the word or part of the
definition. If it is unsuitable, try again. For example, the GM opens the
dictionary and picks the word 'brine'. This could be used in several different
types of quirk, such as 'User Must Drink A Cup of Brine Before Use' (Usage
Limit), 'Only Recharges in Brine' (Recharge Limit) or 'Produces 10 Gallons
of Brine Per Energy Point Used' (Powerstone Effect).
Another method for creating quirks is to brainstorm ahead of time on the
various types and examples given. It is quite easy to come up with a list
of 20 to 30; when you need a quirk, randomly choose one or just pick one
and cross it off the list.
Game Mastering Powerstones
As nice as it is to have a large powerstone around in case you need it,
they take a long time to recharge. A 60-point powerstone takes two months
to fully recharge! Therefore, if PC mages find powerstones on the bodies
of opponents, they will most likely be partially or entirely empty, especially
if they were just used in the battle.
If PCs find a powerstone on a body, the GM should check to see how full
it is. In general, roll on the skill table (p. B45) to see what percentage
of the energy has been used, then subtract any energy that the mage has
used during battles that day. Smaller powerstones will probably be empty,
if the NPC mage just fought the PCs.
To find out if a NPC mage has a powerstone, make an IQ roll for the character
(modifiers: Dead Broke: no chance, Poor: -6, Struggling: -3, Average: no
penalty, Comfortable: + 1, Wealthy: +2, Very Wealthy: +4, and Filthy Rich:
always).
The size of the powerstone can be determined by what the NPC mage can afford;
a poor mage will only have a powerstone of a couple of points at most, while
a filthy rich one may have a powerstone in the 20 to 40 point range or several
smaller ones.
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