Tomes of Eldritch Lore

Mythos tomes are the repositories of arcane wisdom, terrible secrets, and powerful magic. They provide the seeker of enlightenment with stark truths about reality, existence, and presence of those from outside. For the unwary, such books delineate a path to nightmare, horror, and insanity.
This section summarizes the books of the Cthulhu Mythos most often mentioned in the fiction of the Lovecraft Circle of writers.

Describing Mythos Tomes

Some Mythos volumes are recent enough in origin to have been printed with movable type. Those editions were usually published privately in short press runs and only sold to rich collectors or acquaintances. Upon publication, copies often were sought out and destroyed by the authorities due to their scandalous nature. Better these texts be burned and suppressed. Such was the fate of the original publication of The King in Yellow.
Where surviving copies exist, these have often have been ill-treated by the crazed or malicious, or else rebound to disguise their blasphemous contents. Bound manuscripts were never regularized by typesetting and printing, and their wavering, blotted handwriting may be wholly incomprehensible for pages at a time, a situation remedied only by great dedication and scholarship.
Even though each book’s summary is uniform in these rules, assume that each copy of a Mythos book can be different from its fellows. Though the logic of that potential diminishes for recent books, such as Azathoth and Others, even then bindings may be broken, pages torn out, and signatures missing or wrongly collated. Contents may be ink-stained or acid-scarred, with pages half-burnt and the words made illegible or utterly defaced by madmen (or by sane men who sought to destroy the dangerous information therein). Unique information may be written as marginalia or jotted down on notepaper and inserted here or there.
Some tomes begin to possess their own “character” as they grow in age. Passed down through the generations, between family members, booksellers, and collectors, the tomes seem to absorb an imprint of their owners. This can be more than simply the wandering marginalia of occult scholars, with some books apparently manifesting distinct “personalities” that echo once-powerful owners, such as grand sorcerers and cult potentates. Consider the smell, feel, and look of Mythos books. The overall impression ought to be distinctly unhealthy. The binding will probably be leather, perhaps human or even that of some unworldly being. Does the leather leave a slimy residue when touched? Does the book leave a musky odor wherever it has been? Does the presence of the tome cause the pages of other, nearby books to char and blacken? Perhaps the book appears to move of its own accord, never to be found where the investigator remembers placing it.
Sorcerers and cultists are not librarians. They are unconcerned with the needs of posterity. They intend to live forever and they consider the knowledge contained within their tomes to be theirs by right—and not to be lightly passed to the unworthy.

Undiscovered Editions

If an original-language version is found of a work that until then was known only in translation, then the original version is more informative. Add a few percentiles to the Cthulhu Mythos skill reward. Treat the original edition as another edition. The Keeper chooses the book’s original language and can make up its title in that language as well.
If a you create a new Mythos tome for some purpose, you should have a suitable name for it, know the language of its composition, know what it looks and feels like, know how many Sanity points are lost in reading it, know how many Cthulhu Mythos points its comprehension adds, and be able to determine what spells (if any) can be found within it.

Using Mythos Tomes

Despite the dangers, investigators will choose to study this or that terrifying book. The process of reading can be leisurely and can be suspended at any point for as long as need be.
Consider that each book is a potential conduit of Mythos power and energy—a physical and mental portal to the madness of secrets beyond the reasoning of mortal man. Books of power may exert a dark influence on those who possess them, stoking their desire for blasphemous knowledge, kindling a fascination for the occult, and ultimately driving the owner to delve deep into the Mythos and court insanity. In many Lovecraftian stories, the protagonist is thrown headfirst into the horrors of the Mythos as a result of some Mythos artifact or tome.
Akin to spells, Mythos tomes can unbalance a game if used too freely. Such books are a conduit for Cthulhu Mythos knowledge and spells, providing the investigators with a potential source of great power in combating the machinations of the Mythos. If everywhere the investigators turn they find a Mythos tome, then the game can become predictable and the challenge lessened. Obtaining a Mythos book could be a scenario in itself, or at least a suitably dangerous sidetrack to a campaign, allowing the investigators to gain secrets that help them in their quest against the minions of the Mythos.
This power and knowledge comes at a price. In Call of Cthulhu, this usually means an increasing descent into madness. While players will desire to gain Mythos books, they should also fear them, due to the terrible sanity depleting effect they will have on their investigators. Investigator possession of a Mythos tome should always carry a consequence. This may simply be the cost in sanity, as described above, or some other story-related consequence.
Try to devise corrupted investigator background entries that drive the story forward. Think about how the investigator’s relationship with the Mythos tome could be manipulated to compel the game’s narrative, add further depth to the investigator, and suggest roleplaying opportunities to the player concerned. While other investigators view the Mythos tome in question as a smelly, evil-looking book, the investigator who has become corrupted by it will see it in a quite different light. An investigator may feel compelled to hide the book away in case it gets “hurt,” or perhaps the deluded investigator cannot read another book without the tome’s text burning through the print.

The tome is trying to get back to what “it” considers as its rightful owner by sending out messages in the form of dark dreams in the hope that its master will find it. While the investigators suffer from hideous nightmares, the book’s true owner is closing in and waiting for a chance to take back what was stolen.

Possible corrupted investigator background entries:

1. The tome is a source of secrets I must know—I must learn more!
2. No one is allowed to touch my book.
3. The book speaks to me and I must obey.
4. The book is evil, and so am I for reading it.
5. Wherever I put the book it kills anything near to it.
6. The book is changing me—I hunger for human flesh!

The Mythos tome has proved to be most useful, particularly to the investigator who read it (gaining some points in the Cthulhu Mythos skill and a couple of spells). However, the loss of sanity caused by reading tome is manifesting as an unhealthy obsession with the book. The Keeper decides to give the investigator a new “corrupted” entry in their background (under Treasured Possessions): “Will not part with the Book of Iod, takes it wherever he goes.”

Mythos books may also provide the inspiration for investigator delusions (see Insanity side-effects 2: Delusions and Reality Checks, page 162 CoC7eCoreRulebook). Perhaps the book somehow influences the investigator or the investigator sees the book everywhere—even though it was apparently destroyed. Delusions centered on a Mythos tome can have all manner of effects upon the investigators, whether to throw them offtrack or guide them through insane insight.

A Note About the Entries

Information about the tomes described may be known by erudite bibliophiles, historians, and by a few in the rare book trade. While it is unlikely that such books will be found on the shelves of the common public library, some can be found in the rare book sections of certain universities and in private collections. Apart from those listed, other versions, as well as lesser Mythos works exist, as do incidental notebooks, diaries, and letters. Keepers are advised to review the entries for inspiration when designing new volumes of forgotten lore, cultist notebooks, and so on.
Where two dates are noted for multiple Mythos books: the latter date in each case is the date ascribed in the original story. Some dates are conjectural. If available at all, the number of copies listed reflects those known to be held in public and private collections. More existing copies are very likely.
Dimensions given are traditional, since actual sizes often vary between copies. Folios range from 12.5" × 20" to 10" × 15". Quartos vary between 10" × 12.5" and 7.5" × 10". Octavos range between 6.25" × 10" and 5" × 7.5".
The summaries also include average weeks of study per book. When using such numbers, take into account the individual reader’s skills and profession. Use the times and dates given here as comparative indicators of difficulty. Each investigator will study and comprehend a book at a different rate.

Key

Sanity Loss: Automatic Sanity loss for reading the tome.

Cthulhu Mythos: First number shows Cthulhu Myhthos points gained from an Initial reading (CMI). Second number shows Cthulhu Mythos points gained for a Full reading (CMF), see page 174-175 CoC7eCoreRulebook.

Mythos Rating: Percentage chance for finding a useful reference within the tome, see pages 175 CoC7eCoreRulebook.

Study: Suggested time required to conduct a Full reading of the tome.

Suggested Spells: A list of possible spells to be found within the tome.