Best Lovecraftian RPG Supplements for Your Cosmic Horror Campaign

What Are the Best Lovecraftian RPG Supplements for a Cosmic Horror Campaign?

The best Lovecraftian RPG supplement for a cosmic horror campaign is a creature reference a game master can actually use mid-session. Petersen Games' The Anatomical Guide to Lovecraftian Horrors covers more than two dozen Mythos creatures in anatomical detail no standard monster manual bothers with, and it sits alongside a short list of maps, miniatures, and named Great Old Ones that work as physical props at the table.

None of this is an official Call of Cthulhu rulebook. Chaosium owns that line. What follows is the honest version: one genuine reference book built for lore and bestiary work, a handful of Cthulhu Wars pieces GMs repurpose for flavor, and a straight answer on where the actual RPG ruleset comes from.

Which Book Works Best as a Lovecraft Monster Reference for Tabletop RPG?

The Anatomical Guide to Lovecraftian Horrors. It is a Petersen Games book by artist Luis Merlo that treats Lovecraft's creatures like specimens in a natural history text, working out plausible skeletons, organs, and biological mechanics for deep ones, byakhee, flying polyps, and roughly twenty more entries pulled straight from the original fiction.

There are no stat blocks and no rules text inside. That's the point for a GM. A monster manual tells you hit points; this book tells you what a byakhee's wing structure might look like under the hide, which is the kind of detail that turns a one-line encounter into a scene players remember. It's listed under Books on the Petersen Games site, tagged to the Cthulhu Mythos theme, rated for ages 10 and up, and currently priced at $29.99, marked down from $39.99 (prices change, so check the live page before buying). Deep ones first showed up in Lovecraft's 1931 novella The Shadow over Innsmouth; byakhee in the earlier short story "The Festival"; flying polyps in The Shadow Out of Time. All three are public domain literary creatures. Petersen Games owns this specific book and Merlo's specific illustrations, not the underlying monsters.

What Other Petersen Games Pieces Work as Cosmic Horror Campaign Resources?

A short list, and it comes with a caveat. Everything below ships as a Cthulhu Wars board game expansion first. A GM can still get real use out of the sculpts, art, and named lore, just don't expect rules content for a tabletop RPG.

Great Old One Pack 1: Sculpts for Five Named Entities

This $39.99 expansion pack includes Abhoth, Chaugnar Faugn, Cthugha, Mother Hydra, and Yig, five Great Old Ones that are neutral in Cthulhu Wars and can be recruited by any faction. Each comes with its own spellbook fluff text and a colossal miniature. If your campaign features one of these five and your table likes physical stand-ins, the pack gives you a painted reference nobody else is selling as a standalone item.

Dreamlands Map and Yuggoth Map O4: Handouts for Mythos Locations

Both are $39.99 board expansion maps built for Cthulhu Wars, not RPG handouts. The Dreamlands piece depicts the underworld realm from Lovecraft's dream-cycle stories; the Yuggoth map covers the Mi-Go's cold, distant world. Unroll either one on a table during a session set in that location and it does the job a printed handout would do, even though that's not what it was designed for.

Where Does the Actual Call of Cthulhu RPG Ruleset Come From?

Chaosium, not Petersen Games. Sandy Petersen designed the original Call of Cthulhu tabletop RPG, first released in 1981, and Wikipedia's entry on the game confirms Chaosium has published and expanded it ever since, including a seventh edition in 2014. That designer credit is the real connection between Sandy Petersen and Lovecraftian RPGs; it is a history fact, not a claim that Petersen Games publishes or sells the Call of Cthulhu line today.

Chaosium's own site lists the current Keeper Rulebook, Investigator Handbook, and a long shelf of scenario supplements built specifically for that system. If a table needs the actual RPG rules, that's the shelf to shop. Petersen Games' role here is different: creature lore, art, and collectible pieces drawn from the same shared universe. The Cthulhu Mythos itself, the term Lovecraft's contemporary August Derleth coined for this body of fiction, predates both companies and sits in the public domain. Wikipedia's overview of the Mythos traces it back to Lovecraft's 1928 story "The Call of Cthulhu" and the cosmic-indifference themes that followed. Nobody owns Cthulhu, Yig, or the Dreamlands. Companies own their own books, art, and game systems built around them.

How Do You Combine These Resources at the Table?

Layer them by function. Rules come from a real RPG system, whether that's Chaosium's Call of Cthulhu or another engine your group already runs. Bestiary flavor comes from The Anatomical Guide to Lovecraftian Horrors when you need a creature description that goes past "it has tentacles." Physical props, minis for a Great Old One encounter, a map to unroll when the party reaches Yuggoth, come from the Cthulhu Wars catalog even though none of it was written as an RPG supplement.

Painters and collectors already do a version of this without thinking about it: they pick up a reference book before they touch a brush and reach for named sculpts when they want a table centerpiece. Running that same instinct through an RPG campaign instead of a paint station isn't a stretch.

Start with the book if you're building a bestiary. You can pick up The Anatomical Guide to Lovecraftian Horrors directly from Petersen Games, or browse the wider catalog of Cthulhu Wars pieces for the maps and Great Old One packs mentioned above. In-stock orders process within 48 hours; US orders ship via USPS Ground Advantage in 2 to 5 business days, Canadian orders via DHL Ground in 3 to 7 business days, with rates calculated at checkout.