In its simplest form, it works just like regular magic, except Power Investiture replaces Magery, sanctity level replaces mana level and holy items replace magic items.
Another way to go is to represent clerical powers via a series of advantages and powers related to Gods. Appropriate ones include Clerical Investment (p. B43), Blessed (p. B40), Patron (God; p. B72), Healing (p. B59), Oracle (p. B72), Power Investiture (p. B77), and True Faith (p. B97). Appropriate disadvantages include Fanaticism (p. B136), Intolerance (other religions; p. B140), and Disciplines of Faith (p. B132).
Finally, the magic system in GURPS Voodoo and GURPS Spirits works very well for priestly magic, although they are still using 3rd Edition rules. The basic idea is that the caster is calling upon a willful, self-aware power to grant him or her the magical effect asked for. Extended rituals, mystical symbols, and sacrifices can increase the effectiveness, but usually aren't necessary. The spells can be much more far-reaching than standard GURPS magic, but they are more subtle, and usually take long enough to cast that they are not usable in combat except by extremely powerful casters.
Spells with instantaneous effects (e.g., Awaken, Deathtouch) 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, Curse), 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". See M.10.
For the record, Flesh to Stone, Major Healing and Resurrection are all "instantaneous". They produce a momentary pulse of magic that leaves behind a permanent non-magical effect (a statue, healed wound or living human). For a spell to be "lasting" or "permanent," the ongoing effect must be magical, not mundane.
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.
Yes. You're simply more talented with some spells than others.
To learn a spell, a character must know all the prerequisites for that spell. Magery is often not a requirement to learn a spell, and some spells have no prerequisites at all – anyone can learn them. To cast a spell, the character must know the spell, and have Magery in that college or be in a High Mana Zone.
The rules for a mage with One-College-Only Magery are no different. He can learn a spell outside that college, provided he meets all prerequisites for that spell. (If that spell requires Magery, he can not learn it, because his One-College-Only Magery does not apply outside the one college.) To cast that spell, he will need to find a High Mana Zone. Once learned, the spell may be used to fulfill prerequisites for other spells.
EXAMPLE: A mage with One-College-Only Magery in the Illusion college could learn and cast Illusion spells normally. If he wants to learn the Phantom spell (p. G57), he would need Magery 2 in the Illusion college, Perfect Illusion, Hinder, and Apportation. Assuming he had the first two requirements down, he could start by learning Haste (p. M69), and using it to fulfill the prerequisite to learn Hinder (p. M27). Neither of these spells require Magery of any sort to learn. (They each require Magery in the appropriate college to cast, however; he can learn them, but not cast them.) Apportation, however, requires Magery in the college of Movement. He does not have this, so he can neither learn nor cast it; he cannot fulfill the prerequisites of the Phantom spell, even though it is in his chosen college.
The only exceptions to this rule is the spell Recover Energy (p. B248). It may be learned and cast by characters with any Magery at all, even One-College Magery in a college other than Healing. All other prerequisites (namely, that the character learn Lend Energy before Recover Energy) still apply.
When he rolls the dice. In fact, the only thing you have to declare when you first start to concentrate is what spell you're concentrating on. The exceptions are spells like Divination and Seeker, which are worded so as to imply that one must start out meditating on a specific target object or question.
In general, the following things can be left up until the instant the dice are rolled:
You can always recover fatigue while maintaining spells, even if those spells have a nonzero maintenance cost. E.g., if you're maintaining a spell that requires 2 energy every 10 minutes and you have Recover Energy-15 (lets you recover 1 FP per 5 minutes), you can effectively recover energy as fast as you use it.
To figure the reduced casting time of a spell known at very high levels, halve the casting time and round up at each stage (i.e., at skill 20, 25, 30, etc.). Do not just raise ½ to some power and multiply, then round up.
Original Time at Skill Level Time 20 25 30 35 40 . . . 1 1 1 1 1 1 . . . 2 1 1 1 1 1 . . . 3 2 1 1 1 1 . . . 4 2 1 1 1 1 . . . 5 3 2 1 1 1 . . . 10 5 3 2 1 1 . . . 30 15 8 4 2 1 . . . 300 150 75 38 19 10 . . . . . . . . . . . . . . . . . . . . .
Except for the normal Blocking spells, no. That can seem unfair, but this balances nicely with the fact that one-second spells are now uninterruptable by anyone who hasn't taken the Wait maneuver.
This comes from the idea that Concentration is now the equivalent of a Ready maneuver. As good as you can get, you still cannot ready any object instantaneously.* The same is now true for spell concentration.
* I'm ignoring here the Fast-Draw skill, as 1) it's only good for some weapons, and 2) you have to buy it for every type of weapon you have.
For more information about what constitutes a turn in GURPS Fourth Edition, see section 188.8.131.52.
Q: If the condition of the aspected magery is not met, I cannot cast spells at all. So why is the limitation not applied to Magery 0?
A: Because you can still detect magic and use "mage only" items, which is very useful.
Q: The description for "One College Magery" says that "You learn other spells as though you were a non-mage, and can only cast them in high- mana area." The problem is, according to the Basic Set, this limitation doesn't apply to Magery 0, and as long as you have Magery 0, you are a mage and can cast spells in normal mana. So which is right?
A: "One-College Magery" is a special case. The effects listed under its heading under p. B67 apply, meaning you can't cast spells not of your college, or sense magic items that do not have at least one spell of your college, even if you have Magery 0. Accordingly, you should also apply the -40% limitation of "One-College Magery" to Magery 0, lowering its value from 5 to 3 points.
Q: Beside Magery 0, I buy Magery level D (Dancing, -40%) and Magery level S (Singing, -40%). How do I compute my effective Magery level during play?
A: It works like this:
Total cost: 5 + 6*D + 6*S
This is because Magery is now just another leveled bonus like Charisma or Innate Attack, and it's permitted to buy an overall level in pieces, with the various pieces differently limited. Your total level at any given time is the sum of all levels that are currently "active" because the conditions imposed by their limitations have been met.
It would be silly not to allow D+S when dancing and singing; if you did that, it would make more sense just to buy unlimited Magery.
Not normally. As explained under Adding and Improving Skills and Techniques (p. B292), you can only spend earned CPs on new skills if you tried them at default or adventured with others who were using them constantly. Since spells have no default and are cast too quickly to qualify for "constant" use, you can't buy totally new spells with earned CPs. Of course, the GM can always make an exception in unusual circumstances: you received on-the-fly tutorial from the world's best wizard, a god granted you the spells, etc.
To spontaneously "learn" new spells, use Wild Talent (p. B99) with the Retention enhancement and Focused, Magical limitation. Add limitations to taste: Accessibility to cover a requirement like "Must see the spell cast at least once," Preparation Required for a very short period of study, etc.
The standard way to acquire new spells is through study. Learn spells like any other skill, but note that Magery reduces the time required; see Learning Magic (p. B235). Calculate the time needed to earn the necessary CP through study using Improvement Through Study (p. B292).
In certain situations, like when determining what can go through a Force Dome, it's important to define exactly what a "magical" creature is. Although there is no single trait that defines it, it's easy to compose a short list of "markers":
An area spell doesn't have to affect every hex within the spell's radius, but you still pay the full fatigue cost as if you had filled every hex. For instance, Create Fire could call into existence a normal n-hex radius circle of fire, a semi-circle of fire, or a wall, crescent, or bow-tie of fire, as long as they all fit completely within the n-hex radius paid for.
Supernatural creatures such as a demons can walk through a Force Dome (p. M170). The Force Dome keeps out "mundane" creatures.
"Awakened" beings, mages, creatures that don't depend on mana to exist, and creatures that aren't created or summoned magically are regarded as "mundane" as far as standard GURPS magic is concerned. This means that they cannot pass through a Force Dome.
Anything that is caught at the boundary of a Force Dome when it is cast is either dragged into the dome or forcefully expelled. Roll 1d: on 1-3, the object or being is expelled from the dome; on 4-6, it is caught inside.
A Force Dome may enclose a region without mana as long as it meets two criteria: (1) No edge hex of the dome is a hex without mana. (2) The dome is tall enough that the enclosed no mana zone (which extends 12' above the ground) will not cross the dome. Note that a Force Dome must be at least 5 hexes in radius to be 12' or more high at its center.
They interpenetrate, creating three isolated compartments:
****______ ______**** ***/ \/ \*** **/ /\ \** *| 1 |2 | 3 |* **\ \/ /** ***\______/\______/*** **** ****
Force Domes are really spheres of magical energy, with the top hemisphere showing and the bottom hemisphere engulfing mass as a magical (not physical) "anchor". E.g., a 3-hex Force Dome radiates 2 hexes out from the center hex, and is 5 yards (15') in diameter. It must be cast on a patch of ground at least 15' across, and appears to be a "dome" 7.5' high in its center. The other hemisphere is under the ground, full of dirt, stone, or other solid junk. To uncover the whole sphere, cast Disintegrate, Earth-to-Air, Teleport Other or something similar on the mass in the sphere after you have cast Force Dome.
Yes, a Force Dome is worthless in aerial encounters, unless you can cast a large enough dome on the ground that it engulfs you or low-flying foes.
Yes, unless cast on the bottom of a body of water, in which case it makes an exceptional pressurized capsule!
A Force Dome can be cast upon a large, moving platform (like a vehicle) and remain stationary with respect to it, as long as it is completely anchored on the platform; i.e., provided that the lower hemisphere of the dome can be completely contained within the vehicle. Note that in this case, the dome is "anchored" using a big chunk of vehicle, and any electrical cabling, fuel lines, etc. that cross the boundary of the dome will not function!
Yes. If the dome has any contents, gravity will pull them down, bringing the dome with them.
No. The dome can absorb infinite physical force, so the people in the dome would hit the wall and the dome would absorb their kinetic energy, leaving them unharmed. In fact impact with a Force Dome is always harmless.
Nothing, except for the weight of people and dirt inside.
No. Apportation requires a massive, physical subject; a Force Dome is a massless construct of mana, and it cannot be Apported. If you want to move it, use Displace Spell (p. M122).
A Force Dome can absorb infinite amounts of energy - even the blast of a nuclear weapon. It works by converting the absorbed energy to mana and dumping it into the local mana field (perhaps recharging the mana that is used up by wizards).
Contrary to the spell description on p. M170, the energy is absorbed by the Force Dome, not repelled.
Per p. M170, "the Force Dome will repel any physical force or missile spell", even if it has been created magically.
No. Force Dome includes a Weather Dome effect, and the main effect of Weather Dome is that "inside the dome, the air remains fresh."
The problem here is that the Weather Dome spell description is rather vague. However, if it can repel forceful jets of air (as the Windstorm spell) and volcanic ash, per the text, then it seems safe to assume that it can repel airborne dangers in general. Repelling the Windstorm spells means that it maintains constant air pressure, hence the ruling that a Force Dome always contains breathable oxygen-nitrogen at 1 atmosphere (for a human caster), no matter what.
If the caster is not human, the temperature within the dome is always right at the midpoint of the caster's "comfort zone," and the atmosphere is always whatever gas the caster normally breathes, at the pressure he usually breathes it.
Force Dome is intended to be a defense for the caster and his companions, not a prison for the caster's enemies. The spell cannot be evaded or resisted; therefore, allowing mages to trap people in Force Domes to incinerate them, depressurize them, etc. would be abusive, and not in the spirit of the spell.
Still, they can pretty useful for capturing people, especially if you use them for traps in combination with spells not based on physical effects, like Sleep, Flesh to Stone, etc.
If the later spell can cover the whole area of the earlier one (or more), and has precisely the opposite effect, make a Quick Contest between them to determine which one takes effect. But if it's too small to blot out the spell it's trying to blot out, then it just isn't good enough (unless the GM is willing to deal with divided areas).
Although Light spells are not area spells, they do have an area effect since the light is propagating all around. Because of this, the ruling applies to them.
According to Steve, an orange-sized bolt of magical force that hits like a bullet and which quickly vanishes in a blast of fire on impact, detonating any flammables it actually strikes.
About 300 degrees centigrade (570 degrees Fahrenheit).
It is largely an impact weapon; a baseball-sized bolt of pure magical force. This is why it's damage is stopped by the DR of the location hit. It is hot, and it does vanish in a gout of flame when it hits the target, but that's more of a special effect than its primary mode of doing damage.
This "hard" bolt of magical force hits the armor just like a bullet, staff thrust or fist, doing damage on impact, and either denting it a little or punching a hole straight through. It then goes "Poof!" and vanishes in a cloud of fire. It will only heat up a breastplate as much as a baseball-sized globe of 300-degree air would; i.e. not much.
Yes. Here's how it works:
The Explosive Fireball does flame damage – treat as crushing damage that can set fires. It is not a true explosion, but damage decreases with distance in a manner similar to explosive concussion damage. The target may attempt to dive for cover to get away from the center of the blast. DR protects normally; assume torso DR unless the target is hit directly by an Explosive Fireball aimed at another body part.
No. The rules for Missile spells specifically require a Concentrate maneuver to build up the spell. Aim is another maneuver, and not a "free action" that can be added to Concentrate.
Yes. Now you can put up to [Magery * base cost of spell] energy each second in it, for one to three seconds; spell effect is multiplied by each multiple of the base cost. Note that the cost reduction for high skill only applies to the total cost of the spell. With skill 20, you can't cast a 6d fireball for free by concentrating for 3 seconds.
For example, say you have Fireball-15 (basic cost 1) and Magery 4. If you put four points of energy for three consecutive rounds, you would cast a 12d fireball at a cost of (12-1) = 11 energy points. For an Explosive Fireball (basic cost 2d), you could build a 4d one every seconds for seven energy points.
Note that throwing a spell is now done using the Innate Attack skill and is now considered a normal attack (contrary to Third Edition, where it was a free action). Furthermore, don't forget that missile spells can still be dodged or blocked. It could be more cost-effective to shoot 3d Fireballs every two turns than one massive 9d Fireball every four, only to have it dodged.
For non-missile spells, you can also put up to [Magery * base cost of spell] energy points in the spell when applicable, but it can't be built over time. This limit is there simply because these spells can't be dodged or blocked, and allowing many turns for building them would make them abusive. A 9d Deathtouch would be scary indeed!
Basically, you have a penalty of -3 × [# times you've rolled the dice for Major Healing for that person in 24 hours]. This means that you could try to cast it 3 times, fail all 3 attempts and roll at -9 on the fourth, having not yet healed a single point. Note that penalties are calculated separately for Minor Healing and Major Healing. As for Great Healing, you can only do it once per day, so there is no penalty involved.
Counterspell and Dispel Magic are fine for removing magical effects cast on someone by a caster who is empowered to cast spells via a magic item. They have no effect whatsoever on magical effects affecting the wearer of an always-on item. For instance, a Sickness arrow makes the target sick until the arrow is extracted, but a Sickness spell cast by a mage wielding a staff enchanted with Sickness can be Dispelled normally.
No. Spells that produce a permanent change in the world in one, brief flash of magical power don't have lasting magical effects to dispel.
Blocking spells have 0 casting time, but that doesn't exempt them from the ritual requirements for spells. If your level means you need to speak or gesture, and you can't, then you can't cast the spell. (Although at skill 9 or less, twice 0 is still 0, so there's no effect on time.) Assume the words and gestures are very brief; e.g., "Stop!" and a raised hand.
If a "mages only" item would produce an ongoing effect on the user (e.g., Flight), and has Power enough to reduce both its cost to cast and its cost to maintain to 0, then it will generate its magical effect at all times. As such, it is irrelevant who uses it. On the other hand, a "mages only" item that actually empowers the user to cast a spell (e.g., Deathtouch) will only ever work for a mage even if energy cost is reduced to 0. When in doubt, ask yourself the following question: "Does the item effectively grant the user an advantage, or does it just let him cast spells?" If the former, then anyone can use it once cost is reduced to 0; if the latter, then it remains "mages only."
As an example, let's make a generic IQ 14 wizard:
 The general principle in GURPS is that advantages do not raise skill levels for the purpose of defaults. They just add to the base skill level listed on the character sheet. Work out all default structures without bonuses and add any bonuses that apply to particular skills at the very, very end. Or just don't add the bonuses at all, and remember to add them in play.
 Each prerequisite is counted as many time as it appears in the prerequisite chain. Only counting unique prerequisites is an unusable rule for spells very deep within prerequisite trees, if you have to check for overlap of every prerequisite with every other. The idea is to rate the complexity of the spell, and the complexity of its prerequisites, not to count unique, specific spells.
 This looks expensive, but it really isn't. I can default any spell! This system basically means that ritual mages have to buy limited access to all Paths and low levels in many spells as an expensive package. The tradeoff is that they do get all these defaults, and furthermore can raise their spells at the 1 point/level technique cost instead of the 4 points/level skill cost.