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 × P2 +$40 × P.
Number of Gems needed: 1/(0.9815P ).
Labor Cost: average number of castings needed × $25.
Total Cost: (Gem Cost × Number of Gems) + Labor Cost.
Retail Price uses a markup of 100% over the Total Cost.
Zero-Quirk Probability: 0.9717P.
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


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

Number of Quirks

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 TypeQuirk Severity
3-8Use Limit3-10Minor Quirk
9-10Recharge Limit11-13Moderate Quirk
11-12Powerstone Effect14-16Major Quirk
13-15User Effect17-18Severe Quirk
16-18Other Misc. Effect or Limit

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.

(Back to Roleplayer #18 Table of Contents)

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