# The Grand Grimoire of Cthulhu Mythos Magic tags: #game/rpg/grand-grimoire ![[The Grand Grimoire of Cthulhu Mythos Magic (cover).jpg|600]] **The Grand Grimoire of Cthulhu Mythos Magic** is the spellbook of **[[Call of Cthulhu]]** — the biggest, most complete catalogue of Mythos sorcery Chaosium has ever bound between one set of covers, gathered and reworked by **Mike Mason with Matthew Sanderson**. Where the core rulebook gives you the ritual in passing, this is the grimoire: the full weight of the Mythos' magic, organized, explained, and handed to the Keeper with both hands. ## Setting There isn't a setting here so much as a cosmology of sorcery. The **Grand Grimoire** treats Cthulhu Mythos magic as a real, coherent body of forbidden practice rather than a grab-bag of monster tricks: how spells work, what casting actually costs, why some magic goes wrong, and the difference between the things a dilettante can fumble at and the rituals that rearrange your understanding of the universe. It's the magic of the canon collected into one place — folk charms alongside the grand summonings, the spells of Dreamlands natives alongside the flawed, half-remembered rites that should never have been written down at all. ## Mechanics The **Grand Grimoire** is a reference expansion for **Call of Cthulhu** 7th edition (and playable with Pulp Cthulhu), deepening rather than replacing the core magic rules. - **How Mythos magic works** — Mason's framing of spellcasting: the difficulties of it, the components a ritual calls for, the **magical residue** it leaves behind, and the "deeper magic" behind the surface spells. - **Categories of spells** — the big organization (originally by Paul Fricker, expanded by Mason), so the countless spells hang off a real taxonomy rather than a flat list. - **Call / Contact / Summon disambiguation** — the rules for the three most-confused families of rituals, drawn straight from the 7th edition rulebook. - **Folk Magic** — the humble, low-stakes charms and traditions that run alongside the Mythos' grand rites. - **Spirit Attacks and Possession** — the mechanics for the soul-level assaults the Mythos specializes in. - **Dreamlands natives and spells** — the magic of the Dreamlands and those who live there. - **Flawed Spells** — the broken, unreliable rituals, and what happens when casting one goes sideways. - **The spell catalogue** — the enormous, fully-statted body of Mythos spells, each written or revised by Mason with Sanderson, and credited back to the decades of authors (Sandy Petersen, Keith Herber, and dozens more) who originally conjured them. ## Editions - **1st Edition (2017)** — the Magic-Users-unite compendium by **Mike Mason with Matthew Sanderson**, for **Call of Cthulhu** 7th edition. *In the library.* ## References - [The Grand Grimoire of Cthulhu Mythos Magic — DriveThruRPG](https://www.drivethrurpg.com/product/219109/The-Grand-Grimoire-of-Cthulhu-Mythos-Magic)