"Official" Clarifications to the GURPS Magic System
The following information has been taken from "The Words of Kromm" and "The Words of Kromm II" by Sean Punch, the GURPS line editor and rules guru, indexed by Peter Del Orto. Thomas Barnes has edited the text to make it more concise and to combine the two documents. These rulings can be taken as being "official" or at least "semi-official."
Calculating Spell Costs
If a spell can be cast at an increase to base cost to get a greater effect, the increased energy costs are calculated first, before any reductions in skill are figured. For example, a mage who wishes to cast a spell that normally costs 8, 3 to maintain at double cost (16 to cast, 6 to maintain), and has skill 25 with the spell would pay 13 points to cast the spell, and 3 to maintain it (Cost = (8x2)-3 = 13 to cast, or (3x2)-3=3 to maintain). He would need skill 40(!) to cast the double strength version of the spell at 0 cost.
"Casting" a spell equals "rolling the dice for a spell." A mage can only cast one spell (or one normal spell and one Blocking spell) per turn. If the spell fails, he canít cast another one. The exception to this is Combining Spells, see below.
When a spell is cast ceremonially, spectators must personally believe in and feel strongly about the outcome (positive or negative) of a ceremonial casting in order to have any effect on the fatigue available. Single casters can never trade power for skill.
In close combat, or other highly distracting situations, the mage is limited to casting Blocking spells and spells which donít require concentration, such as one-second spells known at 21+ (or 2-second spells known at 25+, 3-second spells known at 30+ , etc.).
In some cases, the GM might allow the mage to cast two spells at once, for example, to create an armed and armored warrior using the Create Warrior and Create Object spell.
Work out the cost and time to cast both spells without including any modifiers for skill, then add the costs and times together. Then apply skill modifiers for the lower skill to the total cost and total time, and roll against the lower skill. For example, if Spell A takes 3 seconds and requires 5 fatigue, and Spell B takes 1 second and requires 3 fatigue, then the total is 4 seconds and 8 fatigue. If a mage knows Spell A at 15 and Spell B at 30, he would apply only the modifiers for the lower level (15) to these figures, giving a casting time of 4 seconds and a cost of 7 fatigue. He would roll against skill 15.
Critical Failure and Effective Skill
The mageís effective skill with a spell, not his Base skill, determines whether or not a roll is a critical miss. For example, if your effective skill is 5, you will critically fail on a 15+! It is a legitimate and effective tactic to fool an enemy mage into thinking that you are much closer to him than you really are, so that he risks critical failure due to unexpectedly high range penalties.
Determining Whether a Spell is Hard or Very Hard
Complexity is generally measured by how long a prerequisite chain a spell has, not the skill difficulty. All VH does is slow the rate at which the spell can be boosted to ridiculous levels, explaining why certain potent spells don't totally alter the face of reality.
If a mage dies while maintaining a spell, if he can make a (Skill+Will-20) roll. If the roll succeeds, the spell becomes permanent if the mage could have maintained it for free due to high skill level.
Multiple does of the same elixir do no "stack" unless the elixir's description specifically allows this. Magic Resistance helps resistance to elixirs.
Ending Spells Prematurely
If a mage spends a point of fatigue to end a spell he takes 1 point of physical fatigue. This fatigue is not reduced for high skill, since it's not really a "mana" cost at all.
Knacks have the same cost to cast and time to cast as the underlying spell. E.g., it takes 1 second to activate a Flame Jet Knack, and it costs 1-3 fatigue/second. Just as for magic items, the "skill" of the Knack (usually 15) does not affect cost or time to cast. For that, you need to apply Power or Speed to the Knack.
No matter what their skill level, Knacks work automatically if there is any mana at all. They are no affected by Low Mana Zones.
Ability to use spells isn't unusual enough to warrant the cost of the Unusual Background advantage in most fantasy worlds.
Limited Magery and Full Magery - If a player wants a mage who has one or more levels of normal Magery, but additional levels of Aspected Magery, he should pay for the normal levels first and then add any extra levels of Aspected Magery after that, to a maximum of 3 levels. For example, a mage with Magery, and two levels of Moon-Aspected Magery, the player would buy Magery 1 normally for 15 points, and add two levels of Moon-Aspected Magery at 5 points each, for a total of 25 points.
Full Magery can be mixed with any form of Magery that gives "split" skill levels dependent on college or situation(i.e., "aspected" Magery): Dark-Aspected (higher level in dark), Moon-Aspected (higher level when moon is out), One College (higher level in college in question), Star-Aspected (higher level at night) and Sun-Aspected (higher level at day). It cannot be mixed with Limited Magery that provides an overall limitation on how you cast spells such as Solitary Magery. There are a few exceptions, Song, Dance, and Musical Magery can all be taken in conjunction with normal Magery, since these are "voluntary" situations. It is also possible to mix levels of Solitary Magery with normal Magery, if the GM rules that they are unusable when someone else is around.
Links and maintained spells cast by the mage fade when his magical powers fade. Spells that are cast, but which donít need to be maintained, persist after the mage has lost his powers until such time as they need to be maintained. Then, since the mage canít maintain them, they end. Note that this limitation includes skills that can be cast at no fatigue, since they still must be maintained. The only exception to this is the Maintain Spell spell, since this makes the spell an entity apart from the caster.
If an Aspected mage does not have Magery due to the limitations of his Aspected Magery, he canít use mage-only magic items. For example, a star mage is only able to use "mage-only" items at night; a song mage has to sing to use "mage-only" items, and so forth.
One College Magery - In most cases, advanced spells with cross-college prerequisites are inaccessible to mages with the One College Only limitation. If you want a mage who's specialized in one college and better at it than most other mages, take Magery 1  and +2 One College Only Magery  in that college.
A mage with One College Magery can learn spells outside of his college, but he but he learns them as though he were a non-mage. If a spell outside his college requires Magery to learn, he canít learn it.
A One College Mage can learn (but not use), Lend ST as a prerequisite for Recover ST.
A mage with one college Magery is only considered to be a mage within his college. To use "mage-only" items, he must either have at least one level of general Magery or stick to items within his college.
Officially, the user of a magic item is treated like a caster, and all the usual limits of the spell apply when casting it through a magic item. The only thing that changes is that the skill of the magic item, rather than the skill of the mage, is used to determine the success or failure of the spell. Magic items use the usual rules for success rolls when casting spells: A power 15 item will fail on 16 and critically fail on 17-18, but a power 16+ item merely fails on 17 and critically fails on 18, just like any other roll vs. skill 16+. Whether or not a critical failure will affect the magic item itself is up to the GM.
Anyone can use a magic item by powering with their own energy, unless the item is restricted to "mages only." Only mages can use Powerstones; a non-mage cannot tap the energy in a Powerstone, even if it is imbedded in a non-mage-only item.
Many people believe magic items are overpriced and underpowered. To make magic items more worthwhile, the GM might introduce the following changes:
- Spells cast using them do not count as spells "on."
- Spells cast using them are unaffected by Shock (although still susceptible to Distraction). This means that the mage must still make a Will roll if he is attacked while using the item.
- Spells cast using them do not count against a mages "running spell count," for spells which have such limits such as Minor and Major Healing.
All magically-summoned or created undead, spirits, creations and the like vanish, melt to goo or go back to Hell when they reach -1 HT. Treat all such creatures as if they had the Unliving disadvantage, p. CI100.
Elementals are not creatures but spirits (see p. M114), as are demons and the forces that inhabit and animate "lesser" undead (mummies, skull spirits, zombies, et cetera) and golems. While some of these entities have well-defined "bodies," none have "minds" per se; on a metaphysical level, they are really magical forces and not conscious beings as such. This means that they cannot be charmed, influenced, possessed or subverted via mind control. A similar prohibition applies to creations: these are magical forces, not conscious beings, and canít be controlled or possessed.
The acid test is a creature's response to the Pentagram spell: if a creature can be confined or held at bay by a Pentagram, then it is magical and cannot normally be affected by spells resisted by IQ.
Magic and Technology
Magic keeps pace with high technology, even if the spells arenít specifically marked at TL spells. For example, at TL8, robots might be common enough foes that Deathtouch/TL8 not only damages flesh and sucks away life force, but also rots insulation and corrodes bearings. This includes Missile Shield, Reflect Missiles, and so forth, which expand to include beam weapons and similar missiles by TL9-10. The GM can slightly alter spell prerequisites as spells change. For example, at TL9 a Missile Shield spell might require some Tech or Light and Darkness spells as prerequisites.
Any spell with a /TL takes normal TL penalties when it has to interact with a higher-TL machine. For example, A TL4 mage is at a -5,-10, or -15 to deal with machines of TL5, 6 or 7, respectively, and canít use his spells on TL8+ machines at all. For example, a TL 4 mage at a -5 penalty to find "the nearest machine" when the nearest machine is a TL 5 steam engine.
The following modifications are appropriate in a game where magic and ultratech combine.
Special Magical Ammo: Ammunition is occasionally enchanted by a by corporations or military formations for use against mages or magical creatures. This is expensive, so this ammunition is quite uncommon. There are two types of special magical ammo:
"Enchanted" rounds are enchanted just to the point where they become magical. They can hence harm magical creatures like Skull Spirits and penetrate Force Domes. The actual enchantment is below the level of a full Accuracy or Puissance enchantment and has no special powers.
"Mana-Drained Rounds" are rounds which have had all of the mana removed from them so they effectively become small, portable no mana zones. They are specifically designed to circumvent the Deflect, Fortify, Missile Shield, Reverse Missiles and Shield spells - nothing else. This property is quite unstable, and is lost once the round has been fired once. Note that since they are unaffected by magic, these rounds cannot be Teleported, will not become Invisible (even if the carrier of the weapon is) and so on.
The two previous properties are mutually exclusive for obvious reasons.
Another common magical munition is the "Jump Trigger". This is simply a switch that is triggered by being magically Teleported. It is normally fitted to grenades and bombs, but occasionally has a more peaceful use. Author: Sean Punch
A mage can maintain spells while recovering fatigue through rest. If the casting cost of a spell is increased, the maintenance cost is increased as well, unless the spell description specifically says otherwise.
Mana Enhancer Advantage
How this advantage is handled depends on how the GM views Gates, Teleportation and Dimensions in his campaign.
If he views teleportation as being the instantaneous, magical transmission of matter through normal space, then the origin, path and destination must all have mana. In this case, someone who has the Mana Enhancer advantage, or who is stuck in an area with mana that is not continuous with the target destination, cannot teleport. This is the magical equivalent of Star Trek teleportation: The subject is magically scanned, converted to "manaon particles," beamed through space and reconstructed at the other end, and a mana-containing pathway is needed to carry the "beam."
If the GM views teleportation as space folding in a higher dimensionality, or as instantaneous travel through a dimensional gateway, then as long as the origin, destination and the space or dimension through which the travel occurs all contain mana, teleportation will work. In this case, someone who has the Mana Enhancer advantage, or who is stuck in an area with mana that is not continuous with the target destination, can teleport, as long as the hyperspace, wormhole or whatever also has mana. This is the magical equivalent of traditional SF teleportation.
There is no "official" right answer. It all depends on the way the campaign works.
If a character with one level of the Mana Enhancer (self only) advantage enters a No Mana Zone on a flying carpet, flying ship, or similar conveyance, the device will still work as long as the character holds onto the vehicle, grasps the wheel, or is actively involved in controlling the vehicle. Otherwise, the vehicle ceases to work. If this seems too powerful, the GM can limit the mage to no more than Heavy encumbrance (like the Teleport spell), or enforce both restrictions.
No Mana Zones
No Mana Zones (NMZ) make ongoing and permanent magic go "dormant." They are not dispelled, but they canít be activated either. Spells which produce temporary or permanent physical effects which arenít inherently magical are unaffected by a NMZ. Missile spells that produce physical effects arenít affected, nor are spell which produce permanent, but mundane effects, such as Exchange Bodies, Flesh to Stone, Major Healing, Resurrection, etc.
The only spells that are affected by a NMZ are spells with ongoing magical effects or spells that rely on mana to defy physical laws. For example, missile spells such as Curse Missile would be dispelled, as would spells such as Flight, Soul Jar, Charm, Enslave, etc.
Spells which have "latent" magic, which isnít triggered in the NMZ are not affected unless they would normally trigger in the NMZ. For example, a NMZ cast on a Link would not automatically cancel the link unless the Link would be activated while the NMZ is in effect, then the Link would be dispelled. If the Link wasnít triggered, it would revert to its "active" status once the NMZ dissipated.
Spells which are maintained still endure (but are "dormant") in a No Mana Zone (NMZ). As long as the mage doesnít have to pay maintenance cost on the spell while he is in the NMZ, the spell will continue and it will come back to full effectiveness when he leaves the NMZ.
Likewise, spells with permanent effects, such as spells with a Permanent duration and Enchantments, wonít work in a NMZ but arenít rendered permanently non-magical.
Information spells canít look into NMZ, nor can they traverse areas without mana if the mage is looking for information in another side of the NMZ.
Spells with instantaneous effects (e.g., Awaken, Deathtouch, Flesh to Stone, Major Healing, Resurrection) never count as spells "on." Non-Instantaneous spells fall into four basic categories. Spells that require fatigue to maintain (e.g., Charm, Light) are temporary spells. Spells that have ongoing effects that require no fatigue to maintain, but which have a limited effective duration (e.g., Bless, Continual Light, Soul Jar), are lasting spells. Spells that have ongoing, permanent effects (e.g., Enslave, Great Geas, Zombie) are permanent spells. Finally, there are enchantments. Of these, only temporary spells count as spells "on."
Temporary and lasting spells are simply dispelled by a no mana zone (NMZ). Permanent spells and enchantments are merely suspended, and resume their normal function once they leave the NMZ.
All but permanent and enchantment spells are ended by a no mana zone (NMZ) - a NMZ merely suspends these classes of spells. Dispel Magic (or the appropriate Counterspell) will end any spell except an enchantment -- even a lasting or permanent one -- unless the spell specifically requires Remove Curse or Exorcism to end it. Note that many lasting and permanent spells do require one of these, though! Finally, Remove Enchantment is the only way to end an enchantment spell.
Resistance against spells is always completely passive, and works normally even if the subject is unconscious or asleep. It is an innate property of living beings to resist spells, not a conscious act.
Spell Appearance and Effects
Unless otherwise stated, spells do not emit visible rays or produce strange ripples that normal people can sense. Mages can sense magical energy by using Magery or the Detect Magic spell. Specific sorts of spells are detailed below.
Area Spells - All Area spells extend 12 feet (4 yards) up from the surface it is cast on. Increasing high requires the mage to increase the energy cost for the spell.
The mage can change the area of an area spell to fit any area that occupies the same amount of space. For example, if a mage casts a 2-hex area spell can stretch it to occupy an area 1 by 7 hexes. The only exceptions are Dome spells, which specifically create (hemi-)spherical areas of effect. To make a wall or other shape with a Dome spell, use the appropriate Wall spell from Grimoire (Force Wall, p. G92 and Utter Wall, p. G93).
If the GM feels that this is unbalancing, he can charge 1.6 times the usual fatigue cost for an Area spell if it is to take any form other than a circle. (This is the same as the +60% for two levels of the Wall enhancement.)
The size of the area, subject, etc. is decided when the dice are rolled to cast the spell.
Mind Control and Communication and Empathy Spells - If the subject of a hostile Mind Control or Communication and Empathy spell resists the spell he will know that he was targeted by a spell, otherwise, he will not know that he has been affected. If the subject fails to resist, nobody will know but the caster. An awake victim feels a resisted mind control spell as a "wrenching sensation." A sleeping victim probably has bad dreams, although someone with Combat Reflexes may roll vs. IQ to wake up immediately.
Missile Spells - Missiles are physical effects created by magic: a big ball of rock, ice or flame, a bolt of electricity, etc. Because they produce a real, physical effect, they can go through (but not be cast) in No Mana Zones (NMZ). The exception to this is spells hurled with Curse Missile, Throw Spell or similar spells, which could not work in a NMZ. You must finish casting the missile spell and hold it "in hand" before you can aim it.
Spell Travel to a Target
A spell always travels from caster to subject via the shortest route that contains mana. If any of that route is in a low mana area, there is a -5 to skill; if there are two routes and only one crosses low mana, the one with the lowest total skill penalty (for distance & mana) will be taken. Distance penalties (regular or long-distance) are figured based on the actual path taken, not the straight-line distance from caster to subject.
This means that a caster can affect a subject who is separated from her by a no mana zone (NMZ), provided her skill is high enough to absorb the penalties for casting around it. Note, however, that if either the caster or subject are in a NMZ, no spell can be cast.
O O O O C O O O O
O O N N N N N N O
O O O O S O O O O
As per the diagram above, a caster (C) and subject (S) stand in hexes of normal mana (O). They are separated by a long, narrow strip of infinitely-tall no-mana hexes (N). C can cast a spell on S, but it must take one of the following routes (*)
O O O O C * * * O O
O O N N N N N N * O
O O O O S * * * O O
O * * * C O O O O O
O * N N N N N N O O
O * * * S O O O O O
This route covers 8 hexes, so the spell is cast at -8, even though the straight-line route:
O O O O C O O O O
O O N N N * N N O
O O O O S O O O O
would only cover 2 hexes. Note that since NMZs created by the Drain Mana spell extend only 4 yards up, the GM may permit the spell to be cast over the barrier. If a mage extends her hand over her head, this looks like:
In other words, the spell must travel 2 yards up, 2 yards over and then 3 yards back down to reach the subject, allowing casting at -7 rather than -8.
Multiple copies of the same spell do not "stack," though stronger versions of the same spell supercede weaker ones. For example, if a mage casts Hinder (for 2 points) on a character with Move 7, then throws Hinder (for 3 points) on the same subject, the victim would be at -3 to Move (the highest level of the two Hinder spells) rather than -5.
This applies to defensive spells (Armor, Shield, Blur), offensive ones (Clumsiness, Hinder, Fatigue), spells that boost abilities (Might, Haste, Climbing), things like Bless and Curse, and any other spell whose effects are leveled but not permanent. Spells which have a permanent effect, such as Deathtouch or Major Healing, could be cast repeatedly to do more damage or healing.