Mythos Grimoires
Sandy Petersen's Cthulhu Mythos - Pathfinder
Ancient tomes of lore and their various translations and versions are a core theme and signature of the Mythos. These books are a major source of power, for both heroes and villains alike, and even the grisly monsters of the Mythos value them.

These books teach not only the rituals and summoning ceremonies for entities of the Mythos, but also provide useful information about the history, nature, and threat posed by them. Knowing that dark young of Shub-Niggurath are solely concerned with serving their terrible Mother is useful information when negotiating with one.

These books also pose a threat. The information they provide may boost a person’s knowledge of Yog-Sothothery, but it also tends to destroy the reader’s sanity and grip on reality. Reading one for the first time is always at least a minor disturbing discovery, and each book may contain multiple such discoveries (see Insanity and Dread).

Each Mythos book is unique, even if multiple copies are known to exist. Different versions of the same text may vary widely in structure and even content. The terrible truth is that all versions are true in their own way, and seeking to reconcile even two copies of the same text has driven many a researcher hopelessly mad. A few of the more famous Mythos books are listed below with some of their traits and features. Many others exist, safely beyond the bounds of mortal knowledge—for now.

Researching a Text

Comprehending the nuances of one of these texts is a challenging process of research that uses the following rules (which have some similarities to the research rules from Pathfinder Roleplaying Game: Ultimate Intrigue). Every Mythos book has a complexity rating, which represents the intricacy or confusing nature of the book’s contents, and a shock rating, which reflects the dangers of investigating the topics in the books for a mortal mind.

To research a specific topic or question within a book, a character must succeed at a research check, using one of the skills listed in the book’s entry. A research check is akin to a Knowledge check, though each book’s stat block lists the specific skills that can be used for research checks based on the nature of that book’s contents, which are sometimes not Knowledge-based.

A book’s complexity rating is the minimum DC for research checks using that book. If a Knowledge check is for a topic with a higher DC, the higher DC is used instead.

Attempting a research check requires an uninterrupted 8-hour period of research, and a character cannot take 10 or 20 on a research check.

Each 8-hour period of research on the same question grants a cumulative +1 bonus on research checks. A character who stops researching a given topic in the same book for a month or more loses any relevant bonuses gained for researching in that book thus far. Up to two additional characters can use the aid another action to assist a primary researcher if they have their own copies of the text or another text on the same topic. Though some research checks cannot normally be attempted untrained unless the research check's DC is 10 or lower (such as if the research check requires a skill that does not allow untrained skill checks), the research of many Mythos books is written specifically to lure in the unwary, allowing untrained checks regardless of the relevant skill.

Succeeding at a research check reveals facts as normal for a successful Knowledge skill check. For every 5 points by which a research check exceeds the DC, further details on the topic (if any) are revealed. Rolling a natural 20 on a research check acts like a critical threat. If the researcher confirms the critical hit by succeeding on a second research check with all the same modifiers (this takes no additional time), two further relevant facts are revealed. Conversely, rolling a natural 1 on a research check automatically results in failure, and the next check takes 16 hours instead of 8, doubling the duration of any dread resulting from that research check (if the researcher's save fails; see below).

The Risks of Mythos Research

Every research check made with one or more Mythos books exposes the reader (and anyone providing aid) to concepts unhealthy for mortal minds to contemplate. Regardless of whether a research check succeeds, the reader must make a saving throw against dread. The save DC of this dread is either equal to the book's shock rating or as normal for a disturbing discovery (see Insanity and Dread) relevant to the topic being researched, whichever is higher. Because disturbing material permeates each text, no topic can be researched that avoids this risk, except in very unusual circumstances (entirely at the GM’s discretion). The dread from this research lasts for 1d3 days or the normal duration for the disturbing discovery, whichever is longer.

If the dread risk or other non-combat challenge related to researching a book's contents is a significant one for player character researchers, the GM is encouraged to award experience points upon a thorough and significant discovery, whether the characters resist the potential insanity or not. Award an amount of experience as if the characters defeated a foe of a CR equal to one-fifth to one-third the book's complexity, depending on the level of risk and/or challenge.

Skill Bonus

Due to the depth and complexity of its content, each of these books grants a bonus on skill checks for skills used for research checks for that book. A book's entry also notes if it allows skill checks untrained. A successful research check is required sometime in the month before attempting the skill check to which the bonus is to be applied.

The researcher must specify the type of skill used but need not know the exact circumstances ahead of time. For example, the researcher may choose to use the Knowledge (arcana) skill, resulting in identification of a spell or arcane topic, while use of the Craft (alchemy) skill might apply to identifying the ingredients and effects of a poison.

Spells, Rituals, and Item Creation Instructions

Many Mythos books contain spells and rituals, but each requires a successful research check to recognize them as such in addition to the normal difficulties of reading spells and rituals. Some also include instructions for creating magic items or alchemical items. A book's skill bonus always applies to checks to learn a spell or ritual from that book as well as to Craft or Spellcraft checks made to create an item from instructions in that book. All spells in these books are found in Mythos Spells. The book's skill bonus doesn't apply to skill checks to cast a ritual, but sometimes the book can be used as an optional focus component for the ritual.

Books of the Mythos

Adventurers and investigators can find and research the following books.

Book of Dzyan

This work is an ancient text from a far away land, which contains “unwelcome truths”—cosmic revelations inimical to any human mind, which the Book tries to reconcile. As such, it describes accounts of mental and physical rites which are protective to mortals, as well as otherworldly threats and how to deal with them. Anyone who casts bard spells can research the spell contrary melody in this book to learn it in place of a 5th-level spell known.

Price 2,765 gp (1,125 gp without rituals and spells)

Complexity 20; Shock 15

Skills Knowledge (arcana, dungeoneering, and planes) and Profession (Yog-Sothothery philosopher); Bonus +2 (untrained)

3rd—secret mouth
4th—protective aura

3rd—impossible arithmetic
5th—contrary melody

The Book of Eibon

Written by the antediluvian wizard Eibon, this is one of the strangest and rarest books on the Mythos. It contains accounts of the many deeds and events of Eibon’s life, as well as those of his contemporaries in ancient Hyperborea, but also recounts his oft-fearsome and compelling prophecies. Eibon traveled to distant worlds, dealt with Tsathoggua face-to-face, and wielded powers so impressive they have lingered in lore and occult tales for tens of thousands of years.

Price 3,690 gp (1,600 gp without rituals and spells)

Complexity 25; Shock 17

Skills Knowledge (geography and history) and Profession (Yog-Sothothery philosopher); Bonus +3 (untrained)

3rd—contact formless spawn, create Elder Sign
5th—bind byakhee, call byakhee

1st—lethargy of Tsathoggua
3rd—sign of Eibon
5th—transport to Yondo, Voorish sign
9th—cursed slumber

The Celaeno Fragments

This was originally a bundle of transcripts written by Dr. Laban Shrewsbury, who claimed to have visited the fabled library of Celaeno in a distant star system. It contains notes about the library itself, other works that are found there, and what Shrewsbury calls the “pantheon” of Outer Gods. Most scholars view the Fragments as an attempt by Shrewsbury to apply logic to the horror and chaos of the universe. But in this attempt, many useful truths are brought to light that test the limits of mortal perception.

Anyone who casts bard spells can research the spell pipes of madness in this book to learn it in place of a 6th-level spell known.

Price 3,020 gp (400 gp without spells)

Complexity 16; Shock 13

Skills Knowledge (dungeoneering and religion) and Profession (Yog-Sothothery philosopher); Bonus +1 (untrained)

3rd—song of Hastur
6th—pipes of madness
7th—hibernation of Ithaqua

Cultes Des Goules

Written by the Comte d’Erlette several centuries ago, this work has two main thrusts. In part, it discusses the structure and beliefs of cults that worship Great Old Ones and Outer Gods, though in a rather general way.

Second, it is a work of the deadliest black magic—a grimoire that contains all necessary information for performing a wide variety of rituals and magic effects. Its greatest weakness is that it has few dismissal or protective effects: its focus seems to be upon the sending of dangerous creatures to an enemy and spells that harm others.

Price 7,200 gp (1,600 gp without rituals and spells)

Complexity 28; Shock 19

Skills Knowledge (arcana and religion) and Profession (Yog- Sothothery philosopher); Bonus +4

3rd—inscribe the Yellow Sign
7th—acid blood curse, bind dimensional shambler, call dimensional shambler
8th—obscene fertility rites of Shub-Niggurath
9th—avatar of the Black Goat with a thousand young

5th—shriek of the byakhee
6th—consume likeness, melt flesh
9th—ferox, tsunami

Eltdown Shards

These fragmentary writings were found in an early Triassic strata on Earth. Two discoveries of the shards were made, in different locations. One consisted of 23 separate tablets, while the second discovery was of 42 tablets, seven of which were common to the first find.

Most of the individual shards are incomplete and some are fragmentary in the extreme. Though discovered from an era in which the great race of Yith ruled that planet, the Eltdown Shards seem to have been written by an enemy of the Yith. They contain information on many pre-human and long-lived races and entities, as well as extensive lore on the nature and weaknesses of the Great Race.

Price 1,670 gp (500 gp without ritual and spells)

Complexity 18; Shock 14

Skills Knowledge (dungeoneering, history, and nature) and Profession (Yog-Sothothery philosopher); Bonus +1 (untrained)

8th—contact Ithaqua

1st—mist of R'lyeh
4th—enlightenment of the Blind Idiot God
6th—wave of oblivion

The King in Yellow

This fabled play might have been penned by the King himself. It has two acts and is rarely performed. The first act is simple, almost banal, while the second act is of unearthly, poisonous beauty that enthralls the mind and soul. Anyone reading it for the first time must make two DC 25 Will saving throws. If the first save fails, the reader gains a major insanity, becoming obsessed with seeking out and serving the King in Yellow. If the second save fails, the reader gains another insanity, generally psychosis. While the play does provide indirect clues about the King in Yellow, Hastur, and their interests, it is usually deemed far too dangerous to read. Readers of this play usually draw the attention of the King and his minions, who might quickly appear. On those rare occasions when the play is performed on stage, the entire audience is exposed as if they had read the play and must make Will saves as described above.

Price — cultists of the King in Yellow and/or Hastur might pay up to 30,000 gp for a complete copy in legible condition

Complexity 25; Shock 25

Skills Knowledge (religion) and Profession (Yog-Sothothery philosopher); Bonus +3 (untrained)

The Necronomicon

This is hands-down the most famous and most lethal of all the ancient books. The original version was penned by Abd al-Azrad, and is also known as Kitab al-Azif. It always contains specific sections about the following:

  • Creatures that live beyond the threshold of material space
  • Information on other planes of existence
  • Formulae for resurrecting the dead, opening gates to other dimensions, and performing dark rituals
  • Instructions for making certain artifacts and alchemical powders and potions
  • Passages with information about a wide variety of Great Old Ones and creatures

It is easily the most complete tome of Cthulhu Mythos knowledge widely known to mortals. However, most copies of the book are incomplete and no two printings (or transcriptions) are even mostly alike.

The book is heavily layered in symbolism, Aklo-based allegory, and other methods of obfuscation. Almost any Mythos spell or ritual can be found within.

Price 30,000 gp (6,300 gp without spells and rituals)

Complexity 30; Shock 20

Skills Knowledge (arcana, dungeoneering, geography, nature, and planes) and Profession (Yog-Sothothery philosopher); Bonus +5 (untrained)

All Mythos Rituals

All Mythos Spells

Pnakotic Manuscripts

Created originally by the great race of Yith, there are over a thousand individual fragmentary bits of scroll that comprise the Manuscripts. They started as excerpts from the great race’s pre-Pleistocene records, but were later expanded upon by prehuman entities, then again in the Dreamlands. They contain scientific, geographic, and historical lore, as well as accounts of dealings with many Mythos beings. For example, fragment 595 contains a lengthy sequence which tells of a battle between yithian forces and some of Cthulhu’s starspawn allies. Because of the incomplete nature of the Manuscripts, the accounts are often frustrating, but they do provide fascinating glimpses into the prehuman universe.

Price 4,100 gp (2,400 gp without rituals and spells)

Complexity 23; Shock 16

Skills Knowledge (engineering, history, nature, and planes) and Profession (Yog-Sothothery philosopher); Bonus +3 (untrained)

4th—brew space mead
5th—contact yithians

6th—ancient sorcery of serpentfolk, nuclear chaos
7th—gaze of Ghatanothoa, vortex

The Revelations of Gla’aki

This is the holy text of the worshipers of Gla’aki, a Great Old One whose cultists are largely undead. When Gla’aki is awake, his slaves/worshipers abide completely under the sway of his will, with no minds of their own. When he sleeps, however, they become autonomous, and during one such period, some of his cultists wrote down fragments of what they remembered from Gla’aki’s mind and their own activities, and what they see as the true nature of the universe. The serious psychoses and breaks with reality suffered by Gla’aki’s victims makes the Revelations non-sequential and difficult to interpret. They provide a terrible and wonderful peek into an alien god’s brain.

Price 2,360 gp (900 gp without spells)

Complexity 24; Shock 17

Skills Knowledge (dungeoneering and history) and Profession (Yog-Sothothery philosopher); Bonus +3

4th—green decay
9th—mimic form of Nyarlathotep

R’lyeh Text

Written in approximately 11,000 BCE on distant Earth, the R’lyeh Text deals most extensively with the deep ones, Father Dagon and Mother Hydra, Great Cthulhu and his starspawn, and so forth. Other related beings (such as Ghatanothoa) are also described, albeit in less detail. It contains prophecies, some of which were long ago fulfilled (such as the sinking of Mu), and others which have not yet been fulfilled (such as the rising of R’lyeh, and the unleashing of the otherwise-unknown Thing That Waits in Darkness).

Price 1,380 gp (400 gp without rituals and spells)

Complexity 19; Shock 15

Skills Knowledge (dungeoneering and history) and Profession (Yog-Sothothery philosopher); Bonus +2

2nd—contact deep ones
5th—call of Cthulhu

2nd—kiss of Dagon
6th—dream sending of Cthulhu
7th—curse of Yig

Seven Cryptical Books of Hsan

These are ancient scrolls penned by Hsan the Greater over two thousand years ago. Each book has a different topic and contains discussions and instructions to execute spells and rituals related to that topic.

Successfully researching one of the Cryptical Book applies a boon to a particular spell or ritual. Generally, the spell or ritual must be of a level lower than the highest-level spell (not ritual) the researcher can cast. Changing which spell the boon applies to requires researching the book again. Some editions of these books also contain spells of the relevant type. The books are most often found individually, rather than as a group, and there is a legend of an eighth Cryptical Book, which is the rarest and most powerful.

Book One

This book discusses the works of the Yellow Emperor and his amazing medicinal abilities. It improves spells dealing with resurrection and life. The researcher adds 1/2 their caster level to the hit points restored by a chosen spell with the healing descriptor.

Price 5,800 gp

Complexity 21; Shock 15

Skills Heal, Knowledge (arcana and nature); Bonus +2

Book Two

This book covers cannibalism, necrophagy, and the disposal of corpses. It improves spells dealing with ghouls, wamps (Dreamlands rivals of the ghouls), and other scavenger-beings. The researcher adds 2 to the DC of a chosen spell when it targets any scavenger.

Price 5,400 gp

Complexity 21; Shock 15

Skills Knowledge (arcana and dungeoneering); Bonus +2

Book Three

This book is on entities of the air. It improves spells for flying beings such as byakhee or hunting horror. The researcher increases the fly speed of any creature conjured or targeted by a chosen spell by 10 feet. When the researcher casts a spell to conjure or control such a creature, that creature takes a -1 penalty on saves to resist the spell.

Price 5,500 gp

Complexity 21; Shock 15

Skills Knowledge (arcana and dungeoneering) and Profession (Yog-Sothothery philosopher); Bonus +2

Book Four

This book examines entities of the earth and subterranean areas. It improves spells for bholes, gugs, and other burrowing beings. The researcher increases the burrow speed of any creature with a burrow speed conjured or targeted by a chosen spell by 10 feet. When the researcher casts a spell to conjure or control such a creature, that creature takes a -1 penalty on saves to resist the spell.

Price 5,400 gp

Complexity 21; Shock 15

Skills Knowledge (arcana and dungeoneering); Bonus +2

Book Five

This book lists entities of time and other dimensions. It contains spells for conjuring up hounds of tindalos as well as a pharmacopeia of drugs that allows users to glimpse other times and to survive space travel. The researcher doubles the duration of a spell that modifies time or conjures a creature separated from time's normal flow.

Price 5,840 gp

Complexity 21; Shock 15

Skills Craft (alchemy), Knowledge (geography), Profession (Yog-Sothothery philosopher); Bonus +2

Item Instructions Plutonian drug

Book Six

This book explains the plateaus of Leng and Kadath, as well as their histories and inhabitants. It includes the formulae for gates that lead to these areas and also to the Dreamlands. The researcher adds 2 to the DC of the chosen spell when it targets a creature from Leng or Kadath.

Price 5,940 gp

Complexity 21; Shock 15

Skills Craft (technology), Knowledge (engineering, history, and planes), and Profession (Yog-Sothothery philosopher); Bonus +2

Item Instructions gate (Kadath and Leng)

Book Seven

This book is devoted to the general pantheon of Mythos gods, focusing especially on Nyarlathotep and Azathoth. It invents a very bureaucratic organization for these deities. The researcher adds 2 to their caster level for a chosen spell associated with Nyarlathotep and Azathoth.

Price 5,400 gp

Complexity 21; Shock 15

Skills Knowledge (religion) and Profession (Yog-Sothothery philosopher); Bonus +2

Von Unaussprechlichen Kulten

Also nicknamed “The Black Book,” this work is most concerned with the history and nature of cults of the Great Old Ones and the Outer Gods, including their organization, beliefs, ceremonial practices, areas of operation. Many extinct cults are described, but also many active ones. Some spells and rituals are here, as well as information on matters like where the corpses of ancient, once-worshiped alien beings are interred.

Price 8,380 gp (3,750 gp without rituals and spells)

Complexity 26; Shock 18

Skills Knowledge (arcana, history, planes, and religion) and Profession (Yog-Sothothery philosopher); Bonus +4 (untrained)

5th—bind star vampire, bride of Sathla, call star vampire
9th—call Father Yog-Sothoth, He Who Must Not Be Named

4th—lesser Sarnath sigil, powder of Ibn Ghazi
7th—dread curse of Azathoth
8th—greater Sarnath sigil
9th—interplanetary teleport

De Vermis Mysteriis

Written by Ludvig Prinn, an ancient alchemist and necromancer who was burnt, De Vermis Mysteriis is an eldritch and bizarre spellbook. Its pages are full of spells and rituals that summon strange entities, familiars, and creatures from beyond space and time. It also has a number of rituals for contacting and dealing with Great Old Ones, Outer Gods, and their minions. A witch can research each of the spells command of the bloody tongue, implant dark young, remortification, and shrivel in this book to teach it to her familiar.

Price 10,785 gp (3,125 gp without rituals and spells)

Complexity 27; Shock 18

Skills Knowledge (arcana, dungeoneering, and planes) and Profession (Yog-Sothothery philosopher); Bonus +4 (untrained)

2nd—call servitor of the Elder Gods
5th—dragon ascending, dragon descending, essential salts
7th—the Red Sign
8th—call hunting horror
9th—call Azathoth

4th—command of the bloody tongue, remortification
6th—implant dark young
9th—temporal energy nexus

The Zanthu Tablets

This is a slim pamphlet-sized translation of carvings from ancient Mu. Originally written by the wizard Zanthu, it contains a history of the lost continent of Mu and discusses the various Great Old Ones worshiped by the Muvians, including Shub-Niggurath amd Ghatanothoa.

Price 895 gp (125 gp without ritual)

Complexity 15; Shock 12

Skills Knowledge (dungeoneering, history, and religion) and Profession (Yog-Sothothery philosopher);
Bonus +1

5th—Mao ceremony

4th—Orne's black
6th—grace of the King in Yellow

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