Custom Spellcasting:
Enhancing The Spell List
In GURPS Magic

By S. John Ross

There can be no question that the GURPS spell list is diverse. The Magic sourcebook boasts over 400 spells, divided into logical groups of skills. This approach gives rise to new a new level of flexibility in gaming magic. The goal of this article is to increase that flexibility a thousandfold, by presenting a simple system of spell modification.

For those of you who use GURPS Supers, the system will already be familiar to you. The enhancements and limitations concept from that book, with only minimal modification, can be applied to spells, giving near-infinite variety as regards specific applications of spells in GURPS. This increases the list of over 400 spells to effectively billions!

Note that ownership of Magic or Supers is not required to use the information in this article, although ownership of Magic is recommended to get the most out of it.

[Blue Room GURPS: The Craig Roth Collection]What Are They And How Do They Work?

Enhancements and limitations can be thought of as "Advantages" and "Disadvantages" for spells. They are used to modify existing spells into altered, or even new ones. For instance, to create a mass-healing spell, you take a Minor Healing spell and apply an Area enhancement to it. This makes it an area spell for all intents and purposes. the cost becomes the base cost, and the mage can now heal several people at once! Note that this is still actually Minor Healing with an enhancement, for purpose of multiple healings, etc.!

All custom spells are Mental/Very Hard, and otherwise learned as normal spells. What is required to know them is discussed later in this article.

How do these effects stay balanced? Each enhancement and limitation is assigned a number from -4 to +4, which affects the level the spell is known at. In the above example, an Area enhancement is a +4 enhancement, so the level of the spell would be reduced by 4. This affects the base level, not just the roll to cast the spell, so casting time and cost are figured at this level. It is as if the caster's IQ had been reduced with regards to this spell. Thus, if Laderell, a mage with an IQ of 12 and Magery 2 were to learn the above spell, it would cost him 16 points to learn it at IQ level. He would have an effective IQ of 12+2-4, or 10. It is a Very Hard skill, and a 12 (Laderell's actual IQ level), costs 16 points (IQ+2).

Fortunately for Laderell, there are limitations which may be taken to offset the cost. Whereas enhancements lower the effective IQ of the student mage, limitations increase it. There is no limit to the amount of enhancement and limitation that can be applied to a spell, unless the GM decides there is in a specific case.

Thus, if Laderell, presently sitting at an effective IQ of 10, decides to apply a -3 limitation (Let's say Recharge, 1 Hour), it would bring him up to a 13, which means he can get it at 12, a respectable level, for only 4 points. He can now "mass-heal", but only once per hour.

Do custom spells work well in a low-mana world? Yes! In fact, they are a great way to make magic less powerful without fading it to the degree that a normal low-mana campaign does. Allowing the players to take limitations to compensate for the -5 penalty strikes a pleasant middle ground.


Accuracy (+1) This enhancement may be bought any number of times, each application of it increasing the accuracy of a missile spell by 1. This enhancement may only be bought for missile spells or spells with the missile enhancement.

Area (+4) This enhancement is applied to any Information, Regular, and some Special spells to create an Area version. The cost to cast becomes the base cost. All other information is unaltered. If applied to a "jet" spell, the the effect will merely radiate from the center from the duration, to the distance determined by the energy placed in the spell. Spell Jet skill is not required for this form of spell, as the attack atuomatically hits anyone in the radius, though it may still be blocked or dodged.

Continuing Damage (+4) This enhancement may be applied to any spell which does damage of any sort. The spell will then do normal damage on the round it hits, and normal damage -2 dice on the second round (including any inherent modifiers. Thus, if a spell does 3d+3 on the first round, it will do 1d+1 on the second). Armor counts as usual for any subsequent damage. If this enhancement is bought twice (+8!!) the reduction rate becomes 1d per turn instead of 2.

Explosive (+3) This enhancement, when applied to a missile spell, causes the missile created to explode on impact. Damage will be full in the hex of impact, and reduced by one die per hex outward (a 2d missile would do 2d in the impact hex and 1d in all adjacent hexes). Like any enhancement or limitation that affects damage done by a spell, it may only be applied to spells that do the damage themselves, that is to say, this cannot be placed on a Poltergeist spell, as it is the force of the object hurled by the spell that actually does the damage! This enhancement may be bought twice. If it is the damage reduction is 1 die per two hexes.

Homing (+4) This enhancement may be applied to any missile spell. The missile in question will never miss its target, so long as it is within range. The target still gets any applicable defense roll.

Link (+1) See "Linking Spells Together," below.

Missile (+4) This enhancement is applied to any regular, area, or information spell, to make it eligible to be linked with a missile spell. It must always be accompanied by a Link enhancement. Spells with this enhancement are assumed to have SS13, Acc 1, 1/2d 20, Max 40.

Fatigue Damage (+3) This enhancement is applied to any spell that does damage. In additon to the normal damage done, the victime loses fatigue equal to the damage taken. In other words, figure damage normally with DR and damage type taken into account, and apply fatigue equal to final damage.

Movable Area (+3) This enhancement may be applied to any spell with a duration of one second or longer. It causes the area to be centered on a subject object or person, and to move with that subject.

No Obvious Effect (+3) This enhancement may be applied to any spell that has some obvious sign of operation (GMs discretion based on his view of the spell). Such a spell with this enhancement is noiseless, invisible, etcetera. If this enhancement is used to create an invisible missile (one of the more common uses of the spell), it may still be actively defended against, but at a -4!

Extended Range (+1) This may be purchased any number of times, each application increasing the 1/2 D of a missile by 5 yards, and the Max by 10.

Selective Explosion (+3) This may be applied only to spells that explode, either Explosive Fireball or a spell with the explosive enhancement (any new spells at the GMs discretion). It allows the caster to choose who or what is affected by his explosions.


Accessibility (Variable) The Accessibilty limitation defines the conditions under which a spell may or may not be cast, or may or may not be effective. This is designed to fill the gaps in the limitations list, by giving guidelines for the creation of new limitations. The Accessibility limitation's value must be determined by the Game Master using the guidelines below.

A -1 limitiation of this sort is relatively trivial. the restricitive event or condition occurs considerably less than half the time (the spell may not be cast in moonlight, for instance). Note that some limitations may be so trivial as to be worthless.

A -2 limitation defines the halfway mark. The spell may be cast about 35%-65% of the time. Only in daylight or darkness, Only works against nonhuman races or a specific gender, only may be cast in- or out-of-doors, etc..

A -3 limitation, the next shade down, makes the spell generally uncommon in use. A spell that only affects dwarves, only works in temples, or can only be cast underwater is such a limitation.

The 4-level limitation opposes the one-level, and then some. Conditions under which a 1 level may be cast, a 4 level may not! A spell that could only be cast on a crowded city street, or only works one hour of the day, or on rare things ("That's odd, Menelaus, this fireball only seems to burn swamp sprites!") would be appropriate.

Note that many of these things listed above change levels depending on the campaign setting. "Only works in the presence of elves" is a -3 level limitation in a normal fantasy campaign, but worth -4 in a 1920s horror campaign (where elves are relatively scarce). In addition, meaningless limitations of other sorts should be avoided. A Create Fire spell with the limitation "cannot be cast on marble" is pointless, since the spell can't be cast on anything, and marble wouldn't burn . . .

Extra Fatigue (-1) For each time you purchase this limitation for anything but an Area spell, the cost to cast is increased by 2. Area spell base costs are only increased by 1. This spell may be bought any number of times.

Fatigue Damage Only (-1) Any spell that does damage may take this limitation, causing the "damage" done by the spell to be only lost fatigue. All normal modifiers, such as armor, impaling damage on an Ice Dagger, fire ignoring armor, etc., are retained.

No Damage (-4) This is applied to any spell that normally does damage, creating a harmless spell (usually missile or jet spells). This is most often used when linking spells to missiles to get better long-range potential, without killing the target. for instance, if you link a total paralysis spell to a lighting bolt, you may not want to kill your target, just hold him still!

Extra Time (-1) Each application of this limitation increases the time to cast by 300%. (a one-second spell with 4 levels of extra time would take 13 seconds to cast).

Shock Only (-2) Damage done with a spell with this limitation on it is not real, but feels real. Shock and stun, and any other factors from pain, are still considered, but no actual injury is done. Armor protects normally.

Physical Effect (-1) This limitation applies only to spells which are not normally accompanied by light, sound, smell, etc. (GMs call). It adds beams, colored light, smoke, crackling noises, sulphurous odors, or some other definite sensory accompaniment to an otherwise covert spell.

Range Limitation (-1) This limitation is applied to missiles, decreasing the 1/2d by 5, and the Max by 10, for each time this limitation is purchased. Range Difficulty (-1) This limitation is applied to regular, area, or information spells. Any penalty for range (spatial or temporal) is doubled, including long-range penalties if applicable.

Recharge (Variable) If this limitation is taken, a certain amount of time must elapse between each casting of the spell. if 5 seconds must elapse, this is a -1 limitation. 15 seconds grants -2, and 1 hour grants -3. 1 week (!) is worth -4.

Touch Only (-2) A regular spell with this limitation requires that the subject be touched. An area spell with this limitation must center on the caster (a staff still counts as an extension of the caster, however). Information spells work on similar principles, depending whether they are area or single-subject spells. Note that some spells already have similar limitations inherent to them, and may not be modified by this limitation.

Ingredient Required (Variable) Some ingredient must be present at the casting of the spell, and is consumed (lost) as the spell is cast, successfully or not. If the ingredient is not consumed, then reduce the value of the limitation by 2. Thus, a -3 level base is required to be worth anything. Value of the limitation is based on the cost of the ingredient. An ingredient costing up to $5 per casting is worth -1. An ingredient worth $25 is worth -2. An ingredient worth $100 is worth -3, and an ingredient worth $1000 or up is -4. Round any odd values to the nearest one to determine the value of the limitation. Note that the ingredient must be in hand, and requires a step and ready manuever. Whether or not a fast-draw skill is applicable is up to the Game Master. For the record, a spell requiring human sacrifice is worth -3, animal sacrifice is worth -2. -4 is reserved for such things as blue-eyed virgins named Cecil.

Custom Magical Items

To determine the cost to make a magical item with a custom spell, just multiply the total modifier by 10% and apply this to the cost to make the item! That is, if you hav an item that normally costs 100 energy to make, with a +2 enhancement and a -3 limitation, the total modifier is -1 so the cost to make the item is 90.

Linking Spells Together: The Link Enhancement

The link enhancement is a much more complicated enhancement, and requires special treatment. many Game Masters may wish to ignore it entirely, but read and consider it first, as it is where the true variety of the system lies.

A link enhancement simply takes two or more spells and combines them into one spell, which is cast all at once, and has a single effect that is a combination of the component spells. This means that you could, for instance, link a fog spell and a mass sleep spell to create a mass sleep spell accompanied by an obscuring mist (perhaps for escape, or just to impress). You could also make combined missiles, or mix combat and non-combat spells for odd effects!

To link a spell to another, take all the spells as separate skills, but all with the link enhancement, noting what spell they are linked to. This forms the composite spell, which is always cast as a single spell. No part of the link may be ignored, unless it is a partial effect optional within one of the spells (GMs call). You must then determine the write-up for the way the new spell will work, using the guidelines below. players and Game Masters should work together at this, as the player knows what effect he has in mind.

A link combination is cast at the lowest level of the component spells for all purposes. If a character has fireball-12 linked to sterilize-11, then the spell is treated as skill level 11.

The general rule of spell combining is this: The least beneficial of the original spells' stats are used. This means that if one of the spells in the link has a time to cast of 1 second and the other 5 seconds, the combination of the two has a time to cast of 5 seconds. A second rule to remember is that if one of the spells has an attribute that the others must share, it must be bought with enhancements. If you have a major healing spell combined with a mass sleep spell, with the intent that all within the area of the sleep will be healed, then you must also apply the area enhancement to the major healing spell. Both of these are general rules, specifics and exceptions for each of the spells "vital statistics" follow. They are in the form of "generic" combinations, by spell type.

Regular/Regular: This is the simplest combination. If the spells involved can be resisted by more than one attribute, use the attribute that comes first in this list: IQ,HT,DX,ST. That is to say, if one is resisted by HT and the other by IQ, then the combined spell is resisted by IQ. Note that duration of spells need not be combined to a single number. One effect can be over and the other continue. Time to cast is determined as above. Cost is the most expensive of the originals, +the number of other spells in the link set (two spells would have a cost of the most expensive + 1).

Area/Regular: These spells may be linked normally, allowing the area effect to center on the subject of the regular spell, or may be linked as a total area spell by giving the regular spell the area link. use the guidelines below for area/area combinations. For the first sort, use the regular/regular rules for cost, time to cast, etc..

Area/Area: Treat as Reg/Reg with the exeption of cost. Base cost is the added base costs of the component spells. This makes combined area effects expensive, so have a powerstone ready.

Information/Anything: Treat the info spell as the closest spell type to it for linking purposes, usually regular or area.

Missile/Regular or Area or Information: The Regular, Area or Info spell must first be given a missile enhancement. This allows the spell to be "carried" by the missile. The main usefullness of this is that the combination spell is treated as a missile spell for all purposes, eliminating the range penalties for most normal spells (you must now hit the target, instead!). For purposes of snap- shot, ranges, etc., use the least favorable of the missiles involved. The missile part of the spell will usually take effect as normal, and the other part (or parts) will as well, but centered at the impact. A clumsiness spell combined with a lightning bolt creates a lightning bolt that does normal damage, and causes a DX reduction in the target. Area spells work in a similar fashion. Casting time for missile spells, remember, are never reduced below one for skill. This applies to linked missiles, as well. Casting times for missile links are listed as "the casting time of the non-missile, or 1 per die of damage, whichever is worse." i.e. A fireball combined with a hush spell would have a casting time of 2 seconds or 1 second per die of damage, whichever is longer. cost to cast is the cost of the non-missile +1, +1 per additional die of damage (up to 2 more).

Missile/Missile: Use the least favorable ranges, the least favorable damage, and the most favorable damage type (player's choice). use the armor effect that the player chooses, as well. Thus, a lightning bolt combined with an ice dagger does 1d-1 per point of energy impaling damage, that tends to ingore metal armor! (No, the damage is not combined.)

Special Note Regarding Resisted Spells: Remember that only one resistance roll is made for the entire spell! In the case of Area/Regular spells. The subject's resistance applies to all effects, and magic resistance counts normally. Any additional targets in the area of effect resistance negated the area effect on them only, and magic resistance counts double. Resistance negates the whole spell if all parts of the spell have a duration longer than instantaneous. Any instantaneuous effects will take affect regardless of resistance, unless they could have been resisted in the original spell.

Learning Custom Spells: Campaign Limits And Balance

There are a few choices to be made if you decide to use custom spells in your campaign. Who can use them? What is required? Does the Link enhancement exist? There are a few more, too. The "default" rules for custom spells is that anyone with Magery 1 can learn and cast them, and prerequisites are as for the spells involved. If you know shape and create fire at 12 or up, you can learn a modified fireball, without neccessarily knowing the basic fireball. That's just the way you learned it. Modified spell may be used as prerequisites themselves. There is no special cost or advantage required. This setup does not disturb game balance and gives players a great deal of leeway in spell choice, by customizing spells in the same way you customize a character; You take some weaknesses to make it better or cheaper or more in line with your image of it.

Many Game Masters, however, may prefer to restrict custom spells in one way or another, and this is a matter of personal taste. The most common way is to remove the link enhancement, which eliminates the GM-work involved in combining spells. An unusual background may be required to learn custom spells, higher levels of Magery, or Research (see p.M00) may be needed. Another method is to rule that the base spells be known as prerequisites (you have to know how to make lightning before you can make lightning carry an illusion spell). Many other restrictions are possible, including the use of enhancements and limitations only for magical items! In this case it is assumed that they are subsumed as special methods of modifying the enchantment structure. Use whatever method you are most comfortable with, and send comments on this to us!

* ARCHIVE NOTE: This is an ANCIENT article, and I'm not really *
* sure I can reccommend its use anymore, but it is popular in  *
* some circles, and I still see it mentioned favorably now and *
* again on the net. So, here it is . . . get from it what you  *
* can.            - S. John Ross, February 1997                *

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