GURPSよろず

The ritual magic system is described on p. B242 (and also GURPS Magic, p. 200). In summary:

• The ritual magician must learn a Very Hard core skill – typically Ritual Magic (p. B218) or Thaumatology (p. B225).

•The magician then studies each college as a Very Hard college skill or path, which has the core skill as a prerequisite, defaults to the core skill at -6, and may never exceed the core skill.

•Each spell is treated as a Hard technique that defaults to the college skill at a penalty equal to the number of prerequisite spells that a wizard would have to know in order to learn it in the standard system. For example, Purify Air (no prerequisites) defaults to Air College skill level, Create Air (prerequisite: Purify Air) defaults to this skill at -1, Shape Air (prerequisite: Create Air) defaults at -2, and so on. Spells can be improved from default as usual for techniques (see p. B230), but cannot exceed the associated path skill.

Ritual magicians can cast spells at default. They can try any spell in any college they’ve studied. In fact, they can attempt any spell at all – although the cumulative penalties from core skill to path to spell can be prohibitive.

Magery adds to core skill (for use in this system, if not for other purposes), path skills, and spells – but only once, not three times over for a spell. If ritual and spell-based magic coexist, then Ritual Magery and standard Magery are separate advantages (but see Varieties of Magery, p. 65).

Many of the ideas in Chapters 2 and 3 apply as readily to ritual magic as to spell-based magic. For example:

• Ritual Magery might take enhancements and limitations.

• Changing the college structure gives rise to a new set of path skills, and may make some spells easier or harder to cast ritually at default. Distributing the same number of spells across more or fewer colleges makes it harder or easier to master a wide range of magics. Obviously, those playing wizard PCs will prefer fewer, broader colleges!

• Clerics might use ritual magic, combining it with Power Investiture instead of Ritual Magery, and leave spellbased magic to secular wizards. Priests will then seem to have a broader, subtler grasp of supernatural power than formulaic, spellcasting wizards, while wizards will be more powerful with the individual spells on which they choose to focus.

• Conversely, wizards may use ritual magic while clerics employ spell-based magic. Wizards then become broadbased theoreticians, while clerics rely on standard “package effects” handed down from above.

“Knowing” Spells to Manipulate Them
Spells that manipulate other spells often require the caster to have some level of knowledge of the magic to be affected. For example, Counterspell works at the lower of the caster’s skills with Counterspell or the spell to be countered, while Ward requires that the caster know the spell to be stopped at 12+. For these purposes, ritual magicians count as “knowing” spells at the level at which they can cast them – at default, if necessary. If they need a point in a spell for some reason, then being able to cast it at skill 10+ is sufficient.

Strange Paths
　For extra weirdness in a world with ritual magic, there may be a few “strange paths”: colleges that are only used ritually, with arbitrary mixtures of spells from the standard colleges linked by a seemingly crackpot magical theory, by their presence in an obscure magical tome, or by some mystic or deity’s teachings. These will often be secret, or at least obscure. Gaining access to them may require buying a perk or even an Unusual Background for each. For some relevant ideas, see the treatment of Books in Chapter 5.

THE PREREQUISITE COUNT
A key factor in ritual magic is a spell’s prerequisite count: the penalty to cast it at default from the path skill. Appendix C (pp. 261-267) provides a table with prerequisite counts for every spell in GURPS Magic. The Spell Table on pp. 223-237 of Magic also gives prerequisite counts, but gamers using the first printing of that book should note that the counts listed there use a variant calculation method (see below).

Variant Count Calculation
A complication that arises in the ritual magic system is exactly how to handle spells that have non-spell prerequisites. It’s easy enough to count prerequisites when only other spells are involved, but some spells list requirements such as minimum IQ scores, Magery, other advantages, and skills. There are a couple of ways to handle this. The simple answer is to require a ritual caster to possess the non-spell prerequisites for any spell he wishes to attempt (even at default) or improve as a technique, reading “Magery” as “Ritual Magery.” This can prevent many strange results. For example, Scroll normally requires substantial literacy in the language used, and removing this prerequisite means that illiterate ritual mages can suddenly start writing magical scrolls! Furthermore, certain spell definitions makes some such prerequisites hard to eliminate on practical grounds; e.g., Fireball lets the caster put energy equal to his Magery level into the spell each second, so a magician without at least Magery 1 can logically get no use out of it.

However, this means that ritual magicians still have to worry about prerequisites, and may be limited in what they can cast, whereas part of the point of the system is that they can attempt any known spell – albeit sometimes with little chance of success. An alternative option is to say that required traits add one to the prerequisite count per 10 full character points that they cost. For example, each level of Magery (with a cost of 10 points) adds one to the count, while literacy (free by default – and never more than 3 points for a new language) adds zero. Forbidden traits, such as “not blind,” have no cost for ordinary characters and hence add nothing. Using this approach means recalculating prerequisite counts for many spells; e.g., Lend Energy requires Magery 1 (10 points) or Empathy (15 points), so its prerequisite count rises from 0 to 1, while Simple Illusion requires the caster to be able to see (no cost) and have at least IQ 11 (20 points), so its count becomes 2.

Using the variant method may require some commonsense rulings; e.g., “No totally illiterate wizard can write a scroll, whatever his skills.” The spells themselves might even need minor adjustments. For example, rather that having Magery prerequisites increase the count for spells such as Fireball, the GM could say that the caster must take a penalty to his roll, and can then put energy equal to the size of the penalty into the spell each turn. This would let a caster who took a -3 penalty sink 3 energy points into his spell in one second and then hurl a 3d Fireball.

Double-Counting of Prerequisites
Another problem with prerequisite counts emerges when the same spell appears in more than one branch of a spell’s prerequisite tree. For example, Create Fire and Shape Fire both name Ignite Fire as a prerequisite (optional, in one case), giving each of them a prerequisite count of 1. Flame Jet requires those two spells, and its listed prerequisite count is 3 – because a wizard who knows just three other spells can learn it. Normally, though, a spell that has two prerequisites, each with count 1, would have a count of 4. The system that gives the lower number is probably fairer and more logical, but if the GM wants a faster and more obviously consistent calculation method, he can find prerequisite counts simply by adding up the number of prerequisite spells and all of their prerequisite counts (giving Flame Jet a count of 4).

Changing the Default Modifiers
If the GM wants to make a specific spell easier or harder to use, then he’s free to change its prerequisite count. He may wish to adjust the spell description and recalculate the count. Alternatively, he might simply change the number by fiat – especially if the campaign doesn’t use standard spellbased magic at all.

For example, Enchant – the most basic spell in the Enchantment college, required by almost anyone who wants to make magic items – requires 10 spells from other colleges, giving it a listed prerequisite count of 10. This makes it nearly impossible to cast at default from the Enchantment College skill without taking that to prodigious levels, and painfully expensive to improve as a technique.
If the GM wants ritual magicians to be effective item-makers, then he might simply reduce the count to 5 and adjust the count for other Enchantment spells downward by a similar amount, making ritual enchantment a challenging but not infeasible career. If he still wants to emphasize that an enchanter needs a broad grounding in magic, then he can give the Enchantment College skill a special prerequisite, such as a point in each of 10 other college skills. Likewise, Curse, with its prerequisite count of 20, is almost impossible for ritual magicians unless the GM lowers its count.

In the other direction, Analyze Magic has a prerequisite count of 3. If the GM wants established spells to be difficult for anyone but a few academic specialists to identify, then he could simply increase that to 10.

Extending the Rule of 20
The standard ritual magic rules create a strong incentive for users to improve the core skill to extreme levels. The most powerful ritual magicians might not put any points into college skills, instead buying an incredible level in the core skill and then working all kinds of magic at default. This may suit some campaigns – but in others, the GM might regard it as abusive or damaging. One solution is to treat any core skill greater than 20 as 20 for the purpose of default calculation, so that college skills never have a default greater than 14. Once a magician reaches that level, his best option is to start putting points into college skills.

No Defaults to Core Skill
Another possibility is to give college skills no default to the core skill. The core skill merely defines the maximum level for college skills. While simple, this option makes it impossible to play an interesting fictional archetype: the dabbler in ritual magic who gains a small amount of unreliable spellcasting ability.

CEREMONIAL CASTINGS
Ritual magicians can use Ceremonial Magic (p. B238), much like wizards under the standard system. An assistant counts as a “mage” if he possesses Ritual Magery and uses the same specialty of the same core skill as the ceremony’s leader. He “knows the spell at level 15+” if he can cast it at that level using the ritual magic system. He “knows the spell at level 14 or lower” if he can cast it at skill 8-14 using that system.

Example: Crassus has Ritual Magery 2 and Ritual Magic (Etruscan)-22. He has Water College-16 by default, which in turn gives him a default Purify Water-15. He, his companions, and a whole cohort of thirsty troops are lost in the Libyan desert – but the pool they’ve just discovered is brackish and undrinkable. Crassus must act as the leader of a ceremony to purify some of the water, despite not having spent any points on that particular college or spell.

His first assistant has Ritual Magery 1, Ritual Magic (Etruscan)-16, Water College-15, and Purify Water-15, and so can contribute as much energy as he can spare. His second has Ritual Magery 2, Ritual Magic (Etruscan)-19, and thus Water College-13 and Purify Water-12 by default; he can contribute 3 points. Unfortunately, Crassus’ friend Laetitia, despite having Ritual Magery 3, bases her magic on the Ritual Magic (Pythagorean) skill, and so counts as a non-mage for the purposes of the casting – just like the totally mundane troops, contributing only 1 energy each.
Between them, they should be able to purify enough to survive.

The generous GM might relax the above restrictions somewhat, permitting ritual magicians with slightly different Ritual Magic specialties – and perhaps even standard spell-based wizards who know the right spell – to assist ceremonies effectively.

KNOWN AND UNKNOWN TECHNIQUES
As written, the ritual magic system gives magicians access to every spell – albeit often at severe penalties. The GM may not want some spells to be available, however. Furthermore, there might be colleges that are imperfectly understood or explored.

The GM could simply delete certain spells, of course. To be fair to the players, he should create the list of unavailable magic at the start of the campaign. He’ll become very unpopular if he bans spells mid-game because he suddenly realizes that they’re troublesome! Reviewing the entire spell list before play begins is a big job, but flexible magic systems like this one always place extra responsibilities on the GM.

However, it’s more interesting if some spells are possible but largely or totally unknown to ritual magicians. They might represent a new field, or merely be so marginal that no one has ever needed them before. Developing such techniques should be a minor but nontrivial research exercise. It ought to be less work than inventing a brand-new spell in a purely spell-based system – because anyone with the appropriate college skill already knows the underlying principles involved – and the ability to cast at default means that there need not be a character point expenditure . . . but some effort should be required. Use Magical Invention (p. 10) as a guideline. The invention skill is usually either Thaumatology or the core skill used for ritual magic. Prerequisite count determines invention complexity:

Prerequisite Count	Complexity
0	Simple
1-3	Average
4-10	Complex
11+	Amazing

ALTERNATIVE CORE SKILLS
In principle, any Very Hard skill could serve as the core skill for ritual magic. Ritual Magic and Thaumatology are the most common choices, and the easiest to explain, but others can be interesting – especially for exotic and limited versions of the system. While IQ-based skills work best, anything is possible given a sufficiently exotic conception of magic:

Alchemy: Magic derives from knowledge of arcane aspects of the material world, or revolves around the art of transmutation. Casting requires use of appropriate potions and reagents, and actual laboratory work in some cases.

Biology: Magic is all about “life energy,” and the manipulation and control of living things. It might be limited to the Animal, Body Control, Communication and Empathy, Food, Healing, and Mind Control colleges.

Body Control: The control of self this skill implies can be extended to control of the world and of magical forces. Colleges such as Body Control (of course!) and Healing are especially appropriate.

Computer Hacking: In a world controlled and maybe even defined by data networks, the true adept of computers can achieve anything. Spellcasting demands access to a terminal (unless one is the transcendent hero of the movie series, which is an Unusual Background).

Herb Lore: Magic is an advanced form of traditional witchcraft, functioning much as the Alchemy-based version (above), but with cheaper materials – and maybe a restriction to fairly subtle effects.

Musical Influence: Truly Orpheus-grade musicians can not only work on the minds of human listeners, but make stones and trees weep, and influence spirits and even the gods. The musician must play or sing to work magic, of course.

Physics: A natural choice in many settings – especially those with a divergent TL (p. B513) that actually means that physical science is pursuing strange and implausible understandings of reality. Frankly, though, with quantum theory and multidimensional interpretations of the universe, Physics/TL8 looks quite bizarre already. Who knows what Physics/TL12 might permit? Spells become procedures involving strange devices and instruments . . .

Pressure Secrets: Casting on other beings requires physical contact – or at least hitting them with a ranged weapon.
This might grant access to the Animal, Body Control, Making and Breaking, and Mind Control colleges.

Weird Science: By definition, this skill concerns itself with things that most scientists would consider insane. This might extend to direct control of paranormal effects. Spells require mad-science gadgets, unless they’re actually based on psychical research.

Of course, a Hard skill isn’t much cheaper than a Very Hard one, and wouldn’t be excessively unbalanced in this application. It’s easy to imagine Esoteric Medicine, Mathematics (Pure), or Religious Ritual, for example, giving access to the arcane. Alternatively, just about any skill could have a Very Hard magical version. Clerics might use “Higher Theology,” or the ultimate traders might negotiate with the universe and always know the price, thanks to “Advanced Merchant.”

DIVINE RITUAL MAGIC
Combining the ritual magic system with Power Investiture and the concept of divine magic (see Clerical Spell-Magic, pp. 65-71) can lead to priests displaying broader, subtler supernatural powers – perhaps in contrast to secular wizards, if the latter use the standard spell-based system. This requires some work from the GM, however.

The core skill for a “ritual cleric” is usually Ritual Magic, with a specialty based on religious rituals. A religious magicworker who knows this skill can go on to acquire one or more “divine college” skills that default to the core skill at the usual -6. The GM should create these skills in place of priestly spell lists (pp. 69-70). The god may grant them through divine inspiration, or priests may learn them as part of their training. Each such college should in turn encompass a spell list, complete with prerequisite counts – which might be exactly as calculated for secular ritual magic, or tweaked to give each temple or cult a distinctive flavor.

Example: Temple of Hephaestus
If the Temple of Hephaestus (p. 70-71) used this system, it might have the following four divine colleges (prerequisite counts appear in parentheses):

Powers of the Shrine: Analyze Magic (3), Animate Object (4), Bless (10), Coolness (2), Create Servant (7), Create Warrior (8), Curse (12), Detect Magic (2), Dispel Creation (6), Divination (Pyromancy) (7), Earth to Stone (1), Extinguish Fire (0), Final Rest (1), Glitch/TL (10), Identify Spell (2), Know Illusion (0), Know True Shape (4), Lend Energy (1), Malfunction/TL (12), Metal Vision (1), Oath (2), Remove Curse (8), Repair (8), Reshape (8), Scryguard (0), Sense Spirit (2), Shape Earth (1), Shape Metal (1), Steelwraith (5), Volcano (9), Watchdog (2).

Powers of Craftsmanship: Animation (4), Borrow Skill (4), Bright Vision (0), Dye (4), Enchant (6), Essential Flame (6), Essential Fuel/TL (5), Find Weakness (1), Fireproof (1), Identify Metal (0), Ignite Fire (0), Inspired Creation (0), Knot (10), Lend Skill (4), Locksmith (1), Mage Sight (0), Magelock (1), Manipulate (2), Measurement (0), Mystic Mark (7), Nightingale (3), Purify Air (0), Recover Energy (1), Reshape (7), Resist Fire (0), See Secrets (4), Seek Fuel/TL (0), Test Load (0).

Powers of the Guardians: Affect Spirits (3), Deflect Energy (1), Fasten (7), Haste (0), Magic Resistance (6), Night Vision (1), Resist Pain (1), Sense Danger (0), Sharpen (3), Vigil (4).

Powers That Are Imbued: Any Enchantment spell not covered by one of the other colleges – except Ensorcel, Great Wish, Lich, Malefice, Manastone, Scroll, Spell Stone, Talisman, Temporary Enchantment, Wish, or Wraith – with their standard prerequisite counts reduced by 1. This college also includes any spell not covered by the other three, with its standard prerequisite count. Such spells can only be used by incorporating them into enchanted items, never cast directly.

Spells described on p. 71 as requiring some level of Power Investiture have the same requirement if cast under this system.

Colleges for Pantheons
Optionally, each god in a polytheistic pantheon might grant one divine college. The spells in such colleges would be closely tied to the associated deity’s sphere of influence.
Ritual spellcasters seeking versatility might have to balance allegiances to a variety of mostly allied but sometimes quarrelsome deities!

Wildcard Colleges
Optionally, the GM can simplify the ritual magic system even further. Simply ignore the requirement for a core skill. Wizards must purchase magical colleges as wildcard skills (see Wildcard Skills, p. B175).
Each spell defaults to the appropriate college skill at a penalty equal to 1/3 of its prerequisite count, rounded to the nearest whole number. Magery adds to college skills, and hence to spells – but this must be Magery of the correct type, if multiple varieties exist in the campaign.

Example: Thaumaticus-Z6G has IQ 15, Wildcard Magery 2, and 12 points in the Air College! skill. He therefore has Air College!-16, and can cast Purify Air at skill 16, Shape Air at 15, and Lightning at 14. This idea may not be especially balanced, but it is quick and usable, and preserves the distinctions between different wizards. Note that the GM and players must still be familiar with the spell lists – for commonly used colleges, at least – to get full use out of it.

See p. 202 of GURPS Magic for an even simpler wildcard system: wizards learn Magic! as a wildcard skill, and may then cast any spell at a penalty equal to its full prerequisite count. This has the virtue of extreme simplicity, but may give wizards too much power for too few points. It’s likely more balanced in a world with low mana.

COMBINING RITUAL AND SPELL MAGIC
Games that feature both ritual magic and the standard spell system can work quite well: spell-users have specialist power, while ritualists enjoy flexibility. Rituals probably pull ahead at high point levels and when working with colleges with lots of fairly simple spells, giving users broad capability for low cost. Wizards might learn both approaches, as the “cookbook” and “first principles” sides of their art – especially if the two use the same type of Magery (see Varieties of Magery, p. 65). Alternatively, each school or style of magic could focus on just one methodology, leading to academic rivalries with a practical edge. As a further complication, ritual magicians and spell-users may use dissimilar college and prerequisite structures, giving the two sides very different views of some tasks.

• 魔法、第4版呪文一覧、原書呪文一覧
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