The heroes of Numeria must brave a remote canyonland known as the Scar of the Spider. Clues found in the Choking Tower revealed that a mysterious prophet left her legacy behind in this valley long ago... a legacy that could reveal methods to defeat the Iron God of the Silver Mount. But the heroes are neither the only, nor the first visitors to the Scar of the Spider, and as they explore, they realize that alien monstrosities have colonized the canyon and have horrific agendas of their own. Can the heroes escape with their brains intact, or will they become merely the latest addition to an otherworldly collection? A Pathfinder Roleplaying Game adventure for 10th-level characters, Valley of the Brain Collectors continues the Iron Gods Adventure Path, an exploration of the lands of Numeria, where savage barbarism clashes with the wonders and horrors of superscience. Several new monsters, an exploration of the mysterious alien empire known as the Dominion of the Black, rules for several strange types of alien technology, and Amber E. Scott's Pathfinder Journal round out this volume of the Pathfinder Adventure Path.