Call of Cthulhu Curse of Chthonians
is a supplement for the Call of Cthulhu roleplaying game published by Chaosium. 

Released in 1984 it contains four detailed scenarios set in the Lovecraftian horror universe. 

The supplement is 88 pages long in its first edition and 160 pages in its second edition. 

It was written by David Hargrave along with William A. Barton and William Hamblin.

The scenarios in “Curse of the Chthonians” are themed around subterranean settings and feature a variety of horror elements, including monsters, mystery, and intrigue. The supplement also includes an examination of Kabbalistic science, specifically the occult practice of Gematria, which involves deriving secret meanings from the letters in words and texts.

One of the notable scenarios included is “The Curse of Chaugnar Faugn,” a 30-page adventure that requires significant integration into a campaign. It features intrigue, sorcery, and an interesting faux climax. 

Another scenario, “The City Without a Name,” involves a journey into the Empty Quarter of Arabia to find the Nameless City, which is fraught with danger and challenges for the investigators.

The supplement is considered a good purchase for Call of Cthulhu enthusiasts, as it provides engaging and detailed scenarios that can be adapted to various campaigns. However, some scenarios may require additional work to make them more engaging for players.