It received positive reviews in game periodicals including Casus Belli, The Space Gamer, White Dwarf, Different Worlds, and Dragon, and is considered to be one of the best roleplaying adventures of all time.

There are a variety of handouts given to the players at various points; these include newspaper clippings, handwritten letters, business cards and a matchbox.

[3] In 1984, while Larry DiTillio was on strike from his job as a television and movie screenwriter,[4]: 37  he earned income by writing role-playing adventures for various companies.

One such assignment was Masks of Nyarlathotep for Chaosium, a five-part adventure for the second edition of Call of Cthulhu that he co-wrote with Lynn Willis.

[4]: 38  A sixth chapter written by DiTillio set in Australia was cut from the final product due to space limitations.

[5] Five years later, Chaosium revised the campaign for the 4th edition of Call of Cthulhu, and published it as a single 160-page perfect-bound softcover book that included eight color plates of scenes from the adventures rendered by Nick Smith, Keith Berdak, Tom Sullivan, and Mark Roland, as well as full color cover art by Lee Gibbons.

In the April 1985 edition of the French games magazine Casus Belli (Issue #25), Martin Latallo questioned the implausibility of ordinary people suddenly uprooting themselves to risk their lives, noting "most of these encounters and discoveries are fatal in themselves, which presents the central problem of the campaign: what can five unfortunate investigators do against an organization which covers the globe and which enjoys the support of the Old Ones?

These modules constitute without a doubt the most deadly campaign ever created by Chaosium, where the stakes are enormous, the dangers immense, and the rewards meager."

"[8] In the November 1985 edition of White Dwarf (Issue #71), Phil Frances lauded this book as "undoutedly the finest... supplement to come from Chaosium."

[4]: 86 In his 2023 book Monsters, Aliens, and Holes in the Ground, RPG historian Stu Horvath noted, "There's something special about this box.

There is an obvious gender imbalance, a good portion of the villains are cliched dark-skinned foreigners, and there are some tasteless depictions of sex rituals."