Sandy Petersen’s Cthulhu Mythos

The Ultimate Guide to the Cthulhu Mythos in Roleplaying

Sandy Petersen’s Cthulhu Mythos is the most comprehensive guide to including Lovecraftian elements in your Roleplaying game, written by the author of the groundbreaking Call of Cthulhu role-playing game, and developed primarily by James Jacobs (creative director of Paizo) and David N. Ross.

This massive tome contains over 100 monster stat blocks, dozens of which are Cthulhu Mythos monsters that have never been described for Pathfinder or Dungeons and Dragons 5e – including new rules for interacting with 25 different Great Old Ones and Outer Gods (they are much more than a simple encounter!).

This is much more than a mere bestiary, however. Inside you will find new rules for Insanity and Dreams; 40 new spells and 30 Rituals – a new magic ruleset; dozens of mythos items and artifacts; dozens of Mythos cults detailed; and four new player races from Lovecraft’s universe – Dreamlands Cats, Mythos Ghouls, Gnorri, and Zoogs – as well as new character options, professions, feats, and race options for them.

5e Fantasy Edition

The 5e Fantasy edition is well over 400 pages long, and was released in late 2018 as a PDF and Summer 2019 as a hardcover. This is not merely a conversion from the Pathfinder edition, but rather a reimagining. It also contains new features, including:

* Over 70 new illustrations not seen in the Pathfinder edition!
* A new avatar of Nyarlathotep, the Dark Demon, as well as more former-human horrors
* Dozens more monsters
* Two new backgrounds (cultist and visionary)
* More Dreamlands denizens
* New character options
* And more!

Enjoy FREE character sheets to help keep track of the action. This beautifully laid out PDF can be printed as often as you like and will be a great enhancement to your friends' Cthulhu-based adventures.

Non-English Editions

Sandy Petersen's Cthulhu Mythos for 5e is now available in German and Italian. To see more details, please click the links below. The book is also planned to be published in French and Spanish in late 2019.

Pathfinder Edition

The Pathfinder edition is a massive 512 pages and was released in 2018. A Pathfinder second edition version is written, and undergoing editing, illustration, and layout. It is expected in 2020.

Dark Eye Edition coming 2019!

Our friends at Ulisses Spiele reached out to us last year requesting to convert the book for their Dark Eye roleplaying game. They are in the process of developing it now, for both their German and English editions!





"...I have rarely received a review item that is so much in my wheelhouse as Ghoul Island. The marriage of the Cthulhu Mythos with my 5E campaign or Pathfinder is like manna from heaven for me. The fact that Sandy Peterson is the person behind this makes it even more appealing."

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A Pawn's Perspective


"Ghoul Island offers a fresh, horrifying adventure that will tax even experienced players, pushing their characters to the brink of insanity...and sometimes over the edge."

— Rob Kalajian

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Board Game Quest


"As a DM I like the excellent plot hooks and flexible options that Ghoul Island offers...I can't wait to have my DnD group play Ghoul Island""

— Brian Winters

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“If you are a fan of horror or interjecting Lovecraftian horrors into your fantasy games, I think that you will really want a copy of Sandy Petersen’s Cthulhu Mythos on your shelves.”

— Christopher Helton

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Talking About Games


“This is one of those books that you will read perhaps 20 pages, and you will feel as if only a couple of minutes passed…Everything is very well written and explained…The illustrations are perfect…notes, by Sandy Petersen himself…A very smooth process to learn how you can implement all of this mythos related information into your Pathfinder roleplaying game….Horror into a high fantasy environment….Overall my highest recommendation for Sandy Petersen’s Cthulhu Mythos. You need to get this book!…A bridge between the Call of Cthulhu Roleplaying game…Lovecraft stories, and the pathfinder roleplaying game…The alien beauty of the cthulhy mythos…dark splendour…dread and insanity…”

— Abraham

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Drive Thru RPG


“Put simply, this book is the best Mythos-themed product for Pathfinder. Period. If you want Cthulhu, or anything related to Cthulhu, this is the book to get.”

— James E.

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“People who are fans of both Cthulhu and Pathfinder will find a lot to love in Sandy Petersen’s Cthulhu Mythos for Pathfinder. Petersen and his team clearly thought through every aspect of the mythos and how it would change in heroic fantasy like Pathfinder. If you’re interested in bringing horror to your Pathfinder game, Sandy Petersen’s Cthulhu Mythos for Pathfinder is well worth the look. It might become your favorite.”

— Beth Rimmels

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Cthulhu Mythos News

Gaming Practicum Video March 17, 2020
Yig Snake Grandaddy February 22, 2020
Yig Snake Grandaddy February 17, 2020
Shout Out to Matt Corley February 5, 2020
More Anatomical Concepts November 10, 2019
More Anatomical Drawings September 19, 2019
Final Opportunity September 9, 2019
Any Anatomy Buffs Out There? September 7, 2019

General Downloads


Yig Snake Granddaddy Gehirs Map 4.45 MB 133 downloads


The Lone Lighthouse 13.21 MB 277 downloads

Dive into the campaign world with a FREE one-shot adventure* (as PDF) that takes...

5E Sagas Character Sheet 3.09 MB 977 downloads

Enjoy this FREE character sheets to help keep track of the action. This beautifully...

Ghoul Island Act 4 Keyless Map 2.89 MB 126 downloads

Some folks have asked for the maps in the adventures without the map key to show...

Ghoul Island Act 3 Keyless Map 3.65 MB 115 downloads

Some folks have asked for the maps in the adventures without the map key to show...

Ghoul Island Act 2 Keyless Map 2.50 MB 109 downloads

Some folks have asked for the maps in the adventures without the map key to show...

Ghoul Island Act 1 Keyless Map 4.48 MB 146 downloads

Some folks have asked for the maps in the adventures without the map key to show...

Ghoul Island Farzeen Gazetteer 2.35 MB 184 downloads

Ghoul Island Saga The remote island of Farzeen rises out of a troubled sea, thousands...

Ghoul Island Act 2 Sample 1.14 MB 180 downloads

The PCs uncover a temple to a Great Old One, Ghatanothoa, and learn the island’s...

Ghoul Island Act 1 Sample 1.02 MB 334 downloads

The PCs’ journey begins in the decrepit port town of Resante. Few call the place...

Cthulhu Mythos Sagas

Get fresh horror delivered to your doorstep EVERY MONTH!

Sandy Petersen, the mind that created the horror RPG genre, brings the Cthulhu Mythos to heroic adventure campaigns for 5e. The Cthulhu Mythos Sagas are full campaigns, taking your adventurers from level 1 to level 14 or 15. They are standalone but can easily be introduced into any fantasy setting.

Each campaign is published in four hardbound volumes, or acts. They are full color, printed on high quality paper with an elegant spot UV hardcover.

Subscription Service Now Available!

Beginning with Cthulhu Mythos Saga II – Yig Snake Granddaddy – we will offer a monthly subscription to the Cthulhu Mythos Sagas. Each month you’ll get a new act of the campaign, and after act 4, the next month will see the release of act 1 of the next standalone Saga.

Subscription Benefits

  • Saga Adventures 20% off retail price
  • Adventures delivered 1 month prior to general retail release
  • Free PDF downloads for each adventure available immediately upon purchase
  • 10% Discount on all roleplaying miniatures
  • Exclusive subscriber discounts and products offered periodically

In Yig Snake Granddaddy, the new Cthulhu Mythos for 5e campaign, evil serpent folk seek to bring back prehistoric times, complete with pterodactyls, dinosaurs, and other monstrous beings.

In Land Out of Time, the first act of four, your player characters adventure into the wilds of Yilan, a primeval wilderness infested with carnivorous slime molds, gigantic crocodiles, and other lost horrors. The heroes encounter an evil serpent wizard, who prepares for an evil ritual beyond belief.

Betrayed, marooned, and hunted by super-intelligent enemies, can the heroes even survive, yet alone prevail?

Yig Snake Granddaddy and the Cthulhu Mythos Saga Subscription will Debut in May 2020

Each act is 75+ full color pages in hardcover...

...with new monsters to fight...

...and new locations to explore!

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Yig Snake Granddaddy - Now Available

Still Not Sure?

Try out the Free 5E-Compatible Cthulhu Mythos Adventure:The Lone Lighthouse for 2-4 characters  of 5th level! 


The Lone Lighthouse

A lighthouse in a stormy bay. An unnatural storm. What began as a simple delivery turns out to be much more than the party asked for. What secrets lie in the lone lighthouse?

Enter the Dark World after the exciting conclusion of Yig Snake Granddaddy!

The next four sagas in your adventure series - coming soon!

Your next 4 months of exciting adventures are coming soon!

Ghoul Island introduces the Cthulhu Mythos to your heroic fantasy campaign as only the mind that created the horror RPG genre can!  Ghoul Island is a full campaign, taking your adventurers from level 1 to level 14.  It will be published in four volumes, each a separate act.

The first act, Voyage to Farzeen, will take PCs from 1st level to 5th.  It begins with a mutiny and ends in the underground tunnels where our adventurers discover an ancient temple dedicated to a horror thought to have been vanquished long ago!  Ghoul Island can easily be introduced into any 5E fantasy campaign and setting!

Each act is 50+ full color pages in hardcover...

...with new monsters to fight...

...and new locations to explore!

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Ghoul Island - Available Now!