Magic in the Mythos

The magic of the Cthulhu Mythos stems from the unfathomable alien intelligences that reside outside of humanity’s ability to comprehend. What may be the pinnacle of science can easily be interpreted as “magic” by the ignorant. What is certain is that those who delve into such matters rarely come away unchanged—usually for the worse! Manipulating time and space is not a thing to be done lightly and there can be grave consequences for those investigators who dabble in things best left alone.
Mythos magic is variable and was not tightly defined by H.P. Lovecraft; each occurrence of magic serves a particular story rather than fitting some consistent overarching structure. However, some generalizations can be made. Mythos magic is traditional in scope, centering on perilous summoning of horrible entities and the desperate manipulation of inimical forces. Spells are formally constructed; one wrong word or gesture can disrupt the spell at best, or cause it to go horribly wrong at worst.
Few Mythos spells can be performed quickly, with many requiring exacting conditions as well as lengthy rites and ceremonies. Each spell must be studied and learned, often requiring the investigator to spend long hours poring over cryptic manuscripts and ancient books of lore. Though rare for investigators, cultists and sorcerers may be taught spells by their fellows, or even granted magical visions, knowledge, and spells through abhorrent communion with the dark gods of the Cthulhu Mythos. Investigators wishing to find a fast track for learning spells are more likely to find a one-way ticket to an asylum, their minds broken and sanity destroyed.
Spells must be approached warily, since often their costs and effects are initially unknown to the spell-caster. For investigators, Mythos magic can be a dangerous trap, for in using it investigators lose Sanity points and gain Cthulhu Mythos knowledge—becoming more like those whom they seek to defeat. Mythos magic bewilders, shocks, disorients, and debilitates its human practitioners. Mankind was not meant to know such things, and with enough exposure the psychic and physical contradictions involved in using magic drive humans insane.
Investigators will mostly experience magic from outside sources, either by being the target or by witnessing the effect of spells cast by someone else. An investigator rarely becomes a mage, since the requisite knowledge and experience usually leads to madness first.
Whether investigators gain much by knowing the magic of the Cthulhu Mythos, they often risk much when attempting to use it. Spells learned while playing published scenarios may prove useful only in the course of a single adventure. Consequently, though all players are invited to study this chapter, it is only Keepers who will benefit most from it when planning adventures and creating suitably objectionable adversaries.

This Section

This section discusses spells and the books of the Cthulhu Mythos—how spells are learned and how they are cast, as well as looking at the dark knowledge contained within ancient tomes. It also discusses the occult versus the magical, and tells ways to increase the POW characteristic.
This section does not contain spells. Mythos spells can be found in Grimoire.

What is Magic?

Gilman had some terrible hints from the dreaded Necronomicon of Abdul Al-hazred…and the suppressed Unaussprechlichen Kulten of von Junzt to correlate with his abstract formulae on the properties of space and the linkage of dimensions known and unknown.

— H.P. Lovecraft, The Dreams in the Witch House

After World War I, astronomers confirmed that the thirty or forty thousand light years of easily observed stars nearest to us comprised only a minor corner of the universe. There was not one Milky Way, as astronomers had once believed, but rather thousands and millions of galaxies, most so faint and so distant that the truth of the nebulae had long been argued, but never before solved. The notion of island universes—galaxies, as we now say—was a bombshell. In the 1920s, humanity’s perception of the unbounded universe’s true size increased by orders of magnitude.
Writing as such discoveries took place, Lovecraft gradually evolved a background myth incorporating such discoveries and added some flavorings from Einstein and Planck. These new “universes,” so he appears to have speculated, were truly islands—their separation included their natural laws. Isolated by hundreds of thousands or millions of light years, the stuff of life could differ wildly. Very quickly, these islands also took on a Riemannian association of existing in or being connected to other dimensions.
The magic of the Cthulhu Mythos is the unifying logic of this universe of universes. Magic works everywhere. It models and defines the greater reality; it is the ultimate expression of natural law, the will of the Outer Gods made palpable and the arbiter of time, space, and matter.
In comparison, earthly science and religion seem of little avail. Apparently we understand far less than we flatter ourselves as knowing. Is imperfection in what we believe or in how we have come to believe it? Perhaps there is a poverty in our souls or our mathematical equations that forestalls ultimate knowledge and revelation. The Mythos mocks human pretensions.

Mythos Tomes

The open book lay flat between us, with the picture staring repulsively upward. As the old man whispered the words "more the same" a tiny splattering impact was heard, and something showed on the yellowed paper of the upturned volume. I thought of the rain and of a leaky roof, but rain is not red.

— H.P. Lovecraft, The Picture In The House

In Lovecraft’s stories, the protagonist usually learns Mythos magic by finding and following written instructions. The volumes of arcane lore mentioned by the Lovecraft Circle of writers represent the intellectual invasion of the Cthulhu Mythos. In particular, these ancient manuscripts and suppressed publications included recipes for the admission (or return!) of the Great Old Ones and the Outer Gods, as described in vivid detail in Lovecraft’s classic story The Dunwich Horror. At least by implication, such writings also indicated how to force away or dispel those dreadful entities.
It takes time to learn, even from textbooks that have been carefully written and specially laid out just for that purpose. Studying the crabbed, idiosyncratic, and infinitely more difficult Mythos books takes much more time and dedication. These musty, thick books are often clumsily scribed by men whose sanity has long since been erased by the horror of their experiments, trials, and conjectures. The present day apparatus of scholarship does not exist in such books. There are no indices, no glossaries, no tables of contents, and no careful definitions. There may not be numbered pages, chapters, paragraphs, punctuation, or even breaks between words. Some tomes might best be described as the ravings of mad men—yet to the seeker of dark knowledge, such texts hold wondrous insights and power.
Many manuscripts are not even in a known alphabet— some are older than time, in languages long lost; others are written in occult ciphers to stymie witch-finders or the Inquisition, and now must be cracked before the would-be reader can ponder the sinister truths they conceal.
Even if a sorcerer wrote for others who were familiar with the arcane and occult, the writing was for adepts and cultists, not laypersons. Strange terms and ideas would be written with no explanation. Valuable annotations might be made by a succession of owners, each perhaps in a different language or with a different aim, and some inscribed in error.
Many Mythos tomes are ancient and must be handled with care. Some are delicate and liable to crumble to dust if the reader doesn’t wear thin gloves and turn the pages with padded forceps. Some whisper that certain tomes are more than merely pages bound in leather; that they are "living" things, intent on sowing their evil taint on the unwary and acting as direct conduits to the horrors of the Outer Gods.
Only in the present does the technology exist with which to make quick and accurate copies

Reading a Mythos Book

Opening a Mythos tome is a dangerous business. It was written by someone who had experienced the Mythos and, if the reader is successful in understanding what is written, this book will act as a conduit to the alien horrors of the Cthulhu Mythos. Opening the cover of a tome might be likened to opening a door to a burning room. By opening this door the reader is exposed to the fire and may be scorched or incinerated. The human mind is metaphorically burnt by the knowledge of the Mythos, the very act of trying to comprehend the material causing the reader to suffer both mentally and physically. Some of the lesser tomes might only be a small fire, but others, such as the dread Necronomicon, are a raging inferno.

When an investigator gains access to a Mythos tome, the Keeper should describe the cover and look of the book. The reader can swiftly ascertain whether the tome is written in a language he or she understands. Refer to Language (other) skill (page 66 CoC7eCoreRulebook) for rules on recognizing and reading other languages. A translator must be found if a book is written in a language unknown by the investigator. The Keeper should decide what gets translated, how quickly, and how accurately. If the language is unknown or long forgotten, the investigators must come up with a plan that convinces the Keeper, or else the book baffles them.

Initial Reading

The next step, beyond looking at the cover, reading the title (if it has one that can be read), and determining the language in which the book is written, is to make an initial reading. To continue the analogy used above, this is where the investigator is exposed to the fire within. An initial reading can be swift and may represent the reader only having skimmed the book sufficient to gain some insight regarding its contents, or it may be a cover-to-cover reading. An initial reading can take as much time as the Keeper wishes; this may be minutes, hours, days, or weeks, depending on how the Keeper wants to shape the story.
Whether a reading roll is called for is up to the Keeper, who may choose to grant automatic success to anyone with a modicum of skill in the appropriate language.
To make a reading roll, the player makes an appropriate Language skill roll on 1D100. The Keeper decides on a difficulty level for reading the book based upon its age, form, and condition (Table XI: Mythos Tomes, pages 237-239 CoC7eCoreRulebook).
A book printed within the last century and in good condition would be of Regular difficulty.
A handwritten work is likely to be of a Hard difficulty level, especially if it is old.
The most challenging of ancient, moldering tomes, containing a mix of print and handwritten annotation, would be Extreme difficulty level.
If the investigator fails the reading roll, they perhaps gets some inkling as to the content of the book, but have failed to comprehend it; no Sanity points are lost and no Cthulhu Mythos skill is gained. The player may ask to push the roll, but must justify doing so, perhaps staying up all night reading or using reference books as an aid to study. When thinking of consequences for failing a pushed reading roll, the Keeper should be creative and include Sanity point loss. If in no hurry, they may continue to read the book without pushing the roll. The timing of the next reading roll is at the Keeper’s discretion (perhaps once per week).
The Table XI: Mythos Tomes (pages 237-239 CoC7eCoreRulebook) indicates the Cthulhu Mythos skill points and Sanity point loss for each tome. Each tome has two values for Cthulhu Mythos: CMI (Cthulhu Mythos Initial) showing how many Cthulhu Mythos skill points are given for an initial reading, and CMF (Cthulhu Mythos Full) that shows how many points are given for full study of the tome.
Once the investigator has made an initial reading, the Keeper should reward them with the initial reading (CMI) number. The reader now automatically loses the Sanity cost of the tome (no Sanity roll is made)—non-believers do not take this Sanity loss (see Becoming a Believer, page 179 CoC7eCoreRulebook).
As well as gaining Cthulhu Mythos skill and losing Sanity points, the initial reading also allows the reader to learn about the contents of book and gain some idea of what spells it might contain. The reader will also have a clear idea of how long it will take to complete a full study of the book.

Harvey gets his hands on the Book of Eibon…

_{Book of Eibon: Sanity point loss 2D4. Cthulhu Mythos +3%/+8%, Full study 32 weeks. Mythos rating 33%.}

The Keeper judges Harvey’s reading of the book to be secondary to the plot and is in no rush for Harvey to complete an initial reading, making it clear to the player that an initial reading is going to take a few days.

Harvey begins reading the book in his home and then continues while on a long train journey. The Keeper decides that Harvey has read for long enough to get something from the book and that the train journey would be a dramatic point to call for a reading roll. As the book is a flawed and incomplete translation, the reading roll is set to Hard difficulty level. Harvey’s player makes the roll and is rewarded with +3% Cthulhu Mythos knowledge (the Cthulhu Mythos Initial—CMI number for the tome) and reduces Harvey’s maximum Sanity points by a corresponding amount. The player is also informed of a number of spells contained within the book. She then rolls 2D4 and Harvey loses 6 Sanity points. This is more that the five points required to trigger temporary insanity, should Harvey’s player pass an Intelligence roll, which she does. The Keeper decides that Harvey loses his mind and pulls the emergency stop cable, bails out of the train, and runs off into the night. The Keeper withholds that information and simply tells the player that Harvey awakens at dawn in a cornfield, his clothes muddy and torn. The Book of Eibon lies in tatters next to him, its pages scattered across the field. Harvey gains “Siderodromophobia— Fear of trains, railroads, and train travel”.

Full Study

He had himself read many of them—a Latin version of the abhorred Necronomicon, the sinister Liber Ivonis, the infamous Cultes des Goules of Comte d'Erlette, the Unaussprechlichen Kulten of von Junzt, and old Ludvig Prinn's hellish De Vermis Mysteriis. But there were others he had known merely by reputation or not at all—the Pnakotic Manuscripts, the Book of Dzyan, and a crumbling volume of wholly unidentifiable characters yet with certain symbols and diagrams shudderingly recognizable to the occult student.

— H.P. Lovecraft, The Haunter of the Dark

A full study of a Mythos tome indicates a comprehensive reading, as one might make when studying an academic work, or as a religious adherent might make of a sacred text. This may involve repeated readings, comparative reading, use of reference works, note taking, and so on. No reading roll is required; if any reading roll was required, it will have been made during the initial reading.
Such a study can take many months. At the end of such a course of study, the reader must make a roll for Sanity point loss appropriate for the tome (if a Believer, see page 179 CoC7eCoreRulebook). The tome’s Mythos rating is then compared with the reader’s Cthulhu Mythos knowledge. If the reader’s Cthulhu Mythos skill is below the Mythos rating of the book, they gain Cthulhu Mythos points equal to the full study (CMF) number. If the reader’s Cthulhu Mythos skill is equal to or above the book’s Mythos rating, they only receive Cthulhu Mythos skill points equal to the initial reading (CMI) number of the book.
Subsequent periods of full study may be undertaken, the difference being that each study will take twice as long as the previous one (double all reading times). Cthulhu Mythos skill increase and Sanity point loss are applied in the same way. In this way a single volume may be studied repeatedly over the years, but each time taking progressively longer than the last, and ultimately with diminishing returns.
In the summaries of Mythos books (see Chapter 11: Tomes of Eldritch Lore CoC7eCoreRulebook), reading times for books are given in weeks. The Keeper should never feel at the mercy of such numbers and should shrink or increase them as appropriate. An outstanding academic with pertinent language skills will read a book faster than an earnest-but-uneducated journalist. Time of study need not be consecutive days, weeks, or months. Note that for a subsequent study of a book, it is recommended that the full reading time is doubled and never reduced.
Only one tome may be studied at a time.

After an hour of careful searching, Harvey collects and collates the Book of Eibon from the cornfield. Later he decides to undertake a full study of the Book of Eibon, knowing that it will take around 32 weeks to complete. At the end of this period Harvey’s player notes that Harvey’s Cthulhu Mythos knowledge is still well below the book’s Mythos rating of 33%, so he gains the +8% Cthulhu Mythos skill points for a full study (CMF). Harvey’s player has already made a reading roll when Harvey made his initial reading, so she does not need to roll again. However, she must make another roll for Sanity point loss (2D4), this time only losing 3 points.

Harvey can begin a further study of the Book of Eibon if he so wishes, but it will take twice as long (64 weeks), at the end of which he would lose another 2D4 Sanity points and gain the full study’s worth of +8% points of Cthulhu Mythos skill (so long as his Cthulhu Mythos skill remains below the tome’s Mythos rating). A third full study would take Harvey 128 weeks (almost two and a half years).

Mythos Rating—Books as References

Once a full study of a tome has been completed, the percentiles entered for its Cthulhu Mythos Rating also quantify its usefulness as a Mythos reference. Such a book may be able to provide a specific fact about the Mythos (such as how long a chthonian takes to reach maturity, or where Y’golonac’s body awaits its resurrection) that might be useful to the investigator’s current situation or line of research.
To research a specific piece of information, the investigator spends 1D4 game hours poring through the book. The player then rolls 1D100; if the result is equal to or less than the book’s Cthulhu Mythos Rating, the investigator finds the fact or an allusion to the fact (the Keeper can express the information as clearly or obscurely as desired). If the roll is failed, either the book does not hold the information or the reader failed to locate it. The user of the book will want to note what was or was not contained.

Increase of Other Skills

Conducting a full study of a tome may grant an increase in other skills as well as Cthulhu Mythos. After a full study of a tome, the reader automatically gains a skill tick for the language in which the book is written, and so their skill in that language may improve in the usual way during the next investigator development phase (see page 94 CoC7eCoreRulebook). The Keeper should also determine whether a particular tome will provide additional benefits to the reader. Increases should be either limited to +1D6 to +1D10 skill points per skill, or simply awarded as a skill tick to be rolled during the next investigator development phase. Other skills that may be improved as a result of reading Mythos tomes include (but are not limited to) History, Archaeology, Anthropology, Occult, Astronomy, and other sciences like Chemistry, Biology, and Physics.

Occult Books

The ideas for handling the information in Mythos books can also apply to non-Mythos books as well. An occult book by definition grants points to the Occult skill after being read. An occult book does not contain knowledge increasing the Cthulhu Mythos skill—otherwise it would be classified as a Mythos book. Some occult books may well include discussions of non-Mythos magic (see Non-Mythos Magic, page 180 CoC7eCoreRulebook), including instructions for spells. An occult book may cost Sanity points if its contents warrant it.

Using Magic

Wisely did Ibn Schacabao say, that happy is the tomb where no wizard hath lain, and happy the town at night whose wizards are all ashes.

— H. P. Lovecraft, The Festival

Increasing the Cthulhu Mythos skill widens the horizons of the student but chips away at mental reserves (reducing maximum Sanity points). However, learning about the Mythos may also let the scholar change reality in specific ways. These “packets of information” are organized as spells. They require activation, measured in the game by Magic points.

Magic Points (MP)

Magic points must (in most cases) be expended to cast spells, as well as to energize artifacts, power magical gates, and so on. An investigator begins the game with Magic points equal to one-fifth of his or her POW; however, cultists and powerful sorcerers often have larger pools of points from which to draw.
Once an individual is out of Magic points, any further expenditure is deducted directly from hit points. Any such loss of hit points will manifest as physical damage in a form chosen by the Keeper—perhaps sores and cuts opening on the body, skin blistering, or blood running from the eyes or ears.
Spending or sacrificing Magic points or points of POW takes only the will of the owner. Doing so may leave sensations of pleasure mingled with regret, a numbness of the soul, or may not be noticeable at all. The spell caster’s essence or energy is channeled into powering the spell.
Some magical attacks leech Magic points or POW from unwilling targets. In those cases, loss may be characterized as being painful or as leaving a headache, or other minor symptoms. Involuntary loss of 10 POW would be a stronger sensation than that of losing the same amount of Magic points.
If Magic points reach zero, the investigator deducts further Magic point loss from hit points (one for one).
Regeneration of Magic points is a natural function, returning at one Magic point per hour (two Magic points per hour for those with POW over 100, three Magic points per hour if POW is over 200 and so on). The number of Magic points cannot regenerate to a value above one-fifth of the character’s POW.
Magic points lost as hit points are healed according to the rules for Wounds and Healing (page 119 CoC7eCoreRulebook). Healing of hit points and regeneration of Magic points can occur concurrently.
Were a character to obtain Magic points of a quantity greater than one-fifth of his or her POW, these could be spent, but the excess could not be regenerated.

Learning a Spell

Learning a Mythos spell does not cost Sanity points; however, casting a Mythos spell does.
Any individual can learn a spell. Studying the Mythos is the last thing a person should do, since increasing Mythos knowledge always brings the character closer and closer to the time when insanity or the Mythos stakes its claim. Sometimes circumstances demand such sacrifice.
Knowledge of a spell can be transferred in three ways, listed below. Learning from a book is by far the most common method.

Learning a Spell from a Mythos Book

Following an investigator conducting an initial reading of a book, the Keeper will indicate the presence and summarize each of the spells in a sentence or two, assuming the book contains spells. The Keeper should not use the rulebook name of a spell, but might instead offer a description like “broughte forth a Great Winged Beast from ye void which did sore crLowde my place of busyness,” in place of the too accurate and too bland Summon Byakhee. Likewise, a spell called “the unremitting terror,” sounds a lot more credible than Implant Fear. Suggestions for alternative names for spells are listed in the Grimoire.
To learn a spell from a Mythos book requires that the investigator has at least made an initial reading of the book. The investigator chooses the spell to study. Learning a spell can take hours, days, weeks, or months (typically 2D6 weeks, but at the Keeper’s discretion). Just as with reading a Mythos book, learning a Mythos spell may be taken up, put aside, and taken up again, as convenient. Usually a roll is called for at this stage; however, the Keeper may choose to grant automatic success, depending on the scenario.
If success is not automatic, the player should attempt a Hard INT roll to learn the spell. If the player fails the roll, the investigator has not learned the spell. The player may ask to push the roll, but must justify doing so; for example, the investigator might lock themselves away in isolation until the is mastered. When thinking of consequences for failing a pushed roll, the Keeper should be creative and include Sanity point loss and strange magical effects—both upon the investigator and their surroundings. If investigator is in no hurry, they may continue to work on learning the spell without pushing the roll. The timing of the next INT roll is at the Keeper’s discretion (perhaps once per two weeks).

Learning a Spell from Another Person

Having learned a spell, a character may teach it to others. One-on-one teaching is quicker than one person learning from a book and, typically, a spell can be learned in one week or less (1D8 days). Use the same rules as for learning a spell from a book, bearing in mind that the process will be faster.

Learning a Spell from a Mythos Entity

At will, any intelligent Mythos entity might supply a book or a scroll detailing a spell. More characteristically, the entity imparts such knowledge by means of dreams or visions; each episode is disturbing and alienating, gnawing away at the character’s sanity and will. This may happen quickly or slowly, as the story requires. A Mythos entity may imbue a complete spell in a character’s mind by telepathy, though such a powerful experience also might send the character directly to the asylum—the Keeper should consider the level of Sanity loss (a minimum of 1D6 is suggested).
Once the process is complete, the Keeper may require the target to make a successful INT roll to retain knowledge of the spell. If this fails, the process must be started anew.
Investigators rarely receive information in this manner; however, cultists often do.

Casting Spells

We have no business calling in such things from outside, and only very wicked people and very wicked cults ever try to.

— H. P. Lovecraft, The Dunwich Horror

Manipulating the forces of the Cthulhu Mythos leads to a loss of Sanity points in amounts that vary by spell. If some awful creature arrives in response to a spell, encountering it costs yet more Sanity points. Having no Sanity points does not prohibit spells from being cast—if it did, there would be no cultists.
Nearly all spells and many magical artifacts also require Magic points (or POW, if that is the need), to be expended, otherwise the spell does not activate and nothing happens.
Physical components may be necessary for particular spells. Such components may be reusable; for example, the great menhirs necessary for summoning He Who Is Not to Be Named (Call Hastur, see page 248 CoC7eCoreRulebook). Other components may be consumed during the spell, such as the drinking of space-mead.
The time required to cast a spell is variable—it may be instantaneous, a few seconds, a game minute, a game week, or longer.
The caster must know the spell and recite a sometimes complex and lengthy chant or rite in authoritative tones. Usually the caster must have complete freedom of movement, since gesture can be as important as chant.
A casting roll is required when a character attempts to cast a newly learned spell for the first time. Once a spell has been successfully cast (even if a pushed roll was required to do so), subsequent uses do not require a casting roll; non-player characters and monsters do not need to make casting rolls.
A Hard POW roll is required to successfully cast a spell the first time. If the casting roll is successful, refer to the spell description for the outcome. If the casting roll is failed, nothing happens.
Following a failed casting roll, the character has a choice whether to make a second attempt to cast the spell (paying the costs a second time)—either immediately or at any time in the future—and, in doing so, push the casting roll.
If the pushed casting roll is successful, the spell works normally without negative consequences. If the pushed casting roll is failed, the spell still works normally, but dire consequences ensue for the caster. Ultimately a spell can always be cast—the casting roll gauges the harm the caster suffers in the process rather than success or failure of the spell.
The only alternative to this (other than giving up on the spell) is to go back to the source and learn the spell again from scratch—usually requiring another 2D6 weeks and a Hard INT roll. After relearning the spell, another initial casting roll may be made—this is a much more cautious approach than pushing the casting roll. This is one of the reasons why wizards seek to extend their lives—miscasting the greater spells can be a fast route to the grave!

Failing a Pushed Casting Roll

The caster must pay the cost of the spell (Magic points, Sanity points, and/or POW) multiplied by 1D6. Any overspend of Magic points is deducted from hit points—this can cause major wounds or death when pushing powerful spells.
The Keeper should add one or more of the following side effects for less powerful spells (choose or roll 1D8). Note that both the caster and others nearby can be affected.

1. Blurred vision or temporary blindness.
2. Disembodied screaming, voices, or other noises.
3. Strong winds or other atmospheric effects.
4. Bleeding—from the caster, others present, or the environment (e.g. the walls).
5. Strange visions and hallucinations.
6. Small animals in the vicinity explode.
7. Foul smell of brimstone.
8. Mythos monster is accidentally summoned.

For more powerful spells (those that summon gods or cost POW for example), the side effects can be worse:

1. Earth shaking, walls rent asunder.
2. Epic thunder and lightning.
3. Blood falls from the sky.
4. The caster’s hand is withered and burnt.
5. The caster ages unnaturally (+2D10 years and apply characteristic modifiers, see Age, page 32 CoC7eCoreRulebook).
6. Powerful or numerous Mythos entities appear, attacking all those nearby, starting with the caster!
7. The caster or everyone nearby are sucked to a distant time or place.
8. Mythos deity is accidentally called.

When hit points are lost as a result of overspending Magic points, the Keeper should narrate the physical harm as a part of the physical consequence of the casting.

Matthew’s initial attempt to cast the “Contact Ghoul” spell has failed, and he has decided to push the roll to try again. Unfortunately, the pushed roll fails too. Matthew has 13 Magic points and 13 hit points.

The cost of the spell is 1D3 Sanity points and 5 Magic points—reduced to 4 Magic points by the Keeper because it is being cast in a moonlit graveyard. Matthew has already paid the cost twice: once for the first attempt and once for the pushed roll immediately after (leaving him 5 Magic points). Now he must pay more. A 4 is rolled on the 1D6 multiplier, so Matthew must pay 16 Magic points (4 MP × 4 = 16) and 9 Sanity points (4D3), as the Mythos power burns through him.

The Keeper describes a sound like thunder as a nearby gravestone explodes, showering Matthew in shards of stone (linking events in the story to the physical damage inflicted by the rules). Matthew must spend 16 Magic points. He has 5 Magic Points left; these are spent and he still owes 11, which must come from his hit points. Luckily, Matthew has 13 hit points and was previously uninjured. The damage reduces Matthew to 2 hit points. Matthew lost over half his hit points in one blow (a major wound) and must make a CON roll to remain conscious. When he recovers, the Sanity point loss will have resulted in insanity. The Keeper amends two of his background entries, one for the wound and one for the insanity.

As the dust settles, Matthew’s friend may notice the pale humanoid figure crouching behind the remnants of the sundered gravestone. The spell worked (as it must when the casting roll is pushed)—time for a Sanity roll!

Evidence of Spells Being Cast

The damage done by a spell is probably obvious. A visible manifestation of a spell being cast may not be so apparent. If it is, one might spot a peculiar hand gesture or body movement, or notice some unusual item or necessary ingredient. In themselves, such effects will begin to establish a tone for Mythos magic, so Keepers are cautioned to keep such effects low-key. However, the effects could be wide-ranging, from hideous roars from beyond, gouts of fire, lines of electrical force, pale nimbuses and auroras of various colors, to the rushing of winds, raised hackles, ionized air, prickly sensations, the stench of sulfur, howling and hissing animals, murmuring voices, alarming moans, or whatever the Keeper thinks fitting.

Disrupted Spell Casting

The casting of a spell will be disrupted if the caster is significantly distracted (physically struck or shot, for example) during its casting.. The Keeper may consult the charts for the consequences of failing a pushed casting roll (see previous page) for inspiration on what might happen. The caster of a failed spell casting must still pay the Sanity point and Magic point costs.

Becoming a Believer

Leng, wherever in space or time it might brood, was not a region I would care to be in or near, nor did I relish the proximity of a world that had ever bred such ambiguous and Archaean monstrosities as those Lake had just mentioned. At the moment I felt sorry that I had ever read the abhorred Necronomicon, or talked so much with that unpleasantly erudite folklorist Wilmarth at the university.

— H.P. Lovecraft, At the Mountains of Madness

An investigator who comes face-to-face with a deep one or a ghoul has an experience that leaves no option but to believe in the cosmic horror of the Cthulhu Mythos. However, reading the Cultes des Goules while safe in an apartment with the lights on, the reader might dismiss the contents as a work of fantasy. This is the player’s prerogative, but disbelief has it perils.
Whether one believes what is read or not, the knowledge is still absorbed. If the character chooses not to believe what is read then the Cthulhu Mythos knowledge granted by the book is added to the investigator’s skill and maximum Sanity points are reduced by the corresponding amount, but no Sanity points are lost. In this way an investigator can accumulate considerable knowledge of the Cthulhu Mythos without losing any Sanity points at all. However, when encountering evidence of the Mythos firsthand, the investigator will realize that those accursed books held the truth! At that point the investigator becomes a believer and immediately loses Sanity points equal to his or her present Cthulhu Mythos score.
Keepers may be relieved that this requires little bookkeeping on their part. The player records their investigator’s gain of Cthulhu Mythos skill as normal and it is that value that is deducted from their Sanity points when becoming a believer.
An investigator can choose to remain a nonbeliever until forced to lose Sanity points for encountering the Mythos firsthand. Viewing human corpses or torture may cause Sanity point loss, but such loss does not lead to belief in the Mythos.
A nonbeliever may read Mythos books and learn (but not cast) spells. Firsthand experience of the Mythos always calls for a Sanity roll, and the loss of one or more of Sanity points compel an investigator to believe in the Cthulhu Mythos thereafter. However, even some firsthand experiences may not convince a disbeliever; if a Sanity roll is passed for encountering a deep one (SAN 0/1D6) no Sanity points are lost and, as such, an investigator might remain a nonbeliever, perhaps rationalizing the creature as Earthly human mutation. However, meeting a clearly unearthly being or a manifestation of one of the gods of the Mythos will always be enough to rip through the façade of the investigator’s beliefs.
An investigator can become a believer at any point the player wishes (and take the Sanity point loss).

How Sorcerers Get That Way

Though investigators rarely have the chance, sorcerers and cultists sometimes swagger around with unseemly amounts of Power (POW). Where did it come from?
When a character successfully casts a spell requiring an opposed POW roll to affect the target, this creates a chance for the caster’s POW to increase through this “exercise”. If the caster wins the opposed POW roll, a subsequent roll to increase his or her POW may be attempted. If the result of a 1D100 roll is greater than the caster’s POW (or the roll is 96 or greater), the caster’s POW increases by 1D10 points permanently.
As a reward for any Luck roll result of 01, POW can be said to have been exercised. Roll the percentile dice and if the roll is greater than the character’s POW, or if the roll is 96 or greater, the character’s POW increases by 1D10 points permanently.
The character may be able to arrange a gift of or a trade for POW from some Mythos deity. The rationale for this is best left to the Keeper. Such an event is likely to increase Cthulhu Mythos as well, and would cost additional Sanity points besides those lost in communicating with the entity.
Increasing Power does not increase current Sanity points.

Ernest has never encountered the Cthulhu Mythos, but found a copy of the Cultes des Goules among his late uncle’s possessions. Having finished an initial reading, the Keeper grants Ernest +4 points of Cthulhu Mythos skill and describes some of the book’s contents and the magical rituals it purports to document. The Keeper then asks whether Ernest believes what he is reading. Ernest is a scientist and has no truck with this superstitious mumbo-jumbo, though he is intrigued by it. Ernest therefore loses no Sanity points as a result of his reading.

Weeks later, Ernest encounters a ghoul while delving around the family vault, and fails his Sanity roll. In addition to the Sanity point loss for seeing the ghoul (1D6), Ernest must also lose Sanity points equal to his present Cthulhu Mythos skill at the revelation that his accumulated knowledge of the Mythos is founded on truth! Ernest loses 6 Sanity points (4 for the Cthulhu Mythos skill points he gained when reading the tome plus 2 for encountering the ghoul). The loss is potentially insanity inducing—Ernest passes his Intelligence roll and goes temporarily insane.

Non-Mythos Magic

Other earthly magic or religiosity can be significant and can have effects in the game if the Keeper wills it. Such earthly “magick” may be real or fraudulent; this is for the Keeper (perhaps in discussion with the player group) to determine.
Mechanics and procedures for such magic should be the same as those for Mythos magic, though the means and aims of earthly magic will greatly differ. If non-Mythos magic is accepted in your game, it is suggested that you tie it to the Occult skill. Horrific deeds should always cost Sanity points.

Optional Rules

Spontaneous Use of the Cthulhu Mythos Skill

Knowledge of the Cthulhu Mythos not only allows a character to learn and cast spells, it also allows someone to improvise magical effects akin to spells. This is resolved in the same way as any regular skill use. The player first states an aim; the Keeper then considers if the aim is acceptable, suggesting a lesser aim in preference to blocking the player’s proposal if possible.
The default difficulty level for use of the Cthulhu Mythos skill in this way is Regular. Alternatively, if the character is using their Cthulhu Mythos skill to affect a target that is resisting them, treat this as an opposed roll between the caster’s Cthulhu Mythos skill and the target’s POW; no further POW-versus POW roll is required. In addition, the Keeper must decide on a cost in Magic points and Sanity points. The Keeper should gauge the cost and make it similar to a comparable spell. The cost and consequence of pushing the Cthulhu Mythos skill roll and failing are the same as those for failing a pushed spell casting roll. The Keeper may allow the player’s aim to be achieved when a pushed roll is failed, however this is not guaranteed as it is for a spell.
Unlike casting a spell, using the Cthulhu Mythos skill to achieve a given effect must be rolled for every time. Some illustrations of spontaneous Cthulhu Mythos skill use:
To cause physical harm to one target: the caster chooses the number of Magic points expended, and loses half that number of Sanity points. To be effective, the caster needs to beat the target in an opposed Cthulhu Mythos versus POW roll. If the caster wins the roll, the target takes damage equal to the number of magic points expended. Nelson extends his hand and screams, “Die!” The veins on his arms bulge and turn black, and he focuses on the approaching beast. Nelson’s player spends 8 Magic points and 4 Sanity points, and then makes a Cthulhu Mythos skill roll, getting a Hard success (below half his skill). The Keeper makes a POW roll for the target, achieving a Regular success–Nelson wins. The Keeper describes the beast’s veins erupting in a mess of gore and deducts 8 hit points.
To banish a monster: the caster spends Magic points equal to one-fifth of the monster’s POW and 1D3 Sanity points. The caster must then succeed in an opposed Cthulhu Mythos versus POW roll against the monster. Enoch stands silently with eyes closed as the dark young of Shub-Niggurath stomps out of the tree line. Enoch has only 14 Magic points and must expend 18 to attempt to banish the monstrosity. He does so; taking 4 hit points of harm (the excess Magic point cost is paid in hit points). He whispers strange words to the beast, uncaring of the bloody tears that are flowing from his now open eyes. Enoch’s player makes a Cthulhu Mythos skill roll, getting a Regular success. The Keeper makes a POW roll for dark young, achieving a Hard success–the dark young wins. The Keeper tells how the dark young strides towards Enoch, who lacks the Magic points to push the roll and so turns to flee.
To commune with the recently deceased: costs the caster 10 Magic points plus 1D10 Sanity points. The effects last a few rounds. Charlie dies just as the investigators get to him. “Tell us who killed you,” they ask him, but it is too late. Placing her hands on Charlie’s chest, Violet implores Charlie to speak. Violet’s player spends 10 Magic points and 3 Sanity points, and then makes a successful Cthulhu Mythos skill roll. The Keeper explains, “You hear Charlie’s words croak from Violet’s throat…” The other players can now talk with Charlie for a few rounds. The Keeper decides enough has been said and says, “Blood begins to bubble up in Violet’s throat. Violet you’re back! But you feel cold, so cold!”

Laurence (Daphne’s investigator) is sure that the ancient stone tablet he holds can yield valuable information, yet he lacks the arcane knowledge required to unlock its secrets. Daphne looks at the Keeper and asks, “What if I try to use my Mythos knowledge to find a way?”

Keeper: “OK, what are you doing?”

Daphne: “Holding the tablet and staring deeply into it, mumbling under my breath.”

The Keeper considers that it would be cool if Laurence could unlock the knowledge in the tablet, as it would move the game on nicely.

Keeper: “OK, it’ll cost you 3 Magic points and 1 Sanity point—give me a roll.”

Laurence has 14 Cthulhu Mythos, Daphne rolls 84—a failure. Nothing happens.

Daphne considers: “Bother! I go outside, under the moon and start yelling out the names of all the Mythos gods that I’ve read about and try to open my mind to the tablet.”

The Keeper likes the sound of this and agrees to a pushed roll. Daphne crosses off another 3 Magic points and 1 Sanity point.

Daphne fails again, with a roll of 34. Laurence will have to suffer the consequences. She rolls 3 on 1D6 for the multiplier (see The consequences of Failing a Pushed Casting Roll, page 178), so Laurence must lose another 9 Magic points (3 × 3) and another 3 Sanity points. Laurence has now spent 15 Magic points, which is more than he possesses, so he loses several hit points as well, leading the Keeper to include physical harm as part of the consequence of failing the pushed roll. Whether Daphne gains any insights is up to the Keeper.

The Keeper describes the consequence: “You are squeezing the tablet so hard that the skin on your hands begins to blister and split. Blood starts to seep out. It crawls across the tablet and begins to form letters. You stare intently at the letters as they form words. You can read the words, they say…”

The Keeper decides to grant Daphne some insight into the knowledge held within the tablet, but at quite a cost to Laurence’s health and sanity