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 crowde 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 Chapter 12: 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 spell 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).
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.
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.
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). 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!