With an army of their own the heroes finally wage war against the Ironfang Legion in the climactic conclusion of the Ironfang Invasion Adventure Path! To end the hobgoblin threat once & for all they must assault the Onyx Citadel—an ancient fortress on the Plane of Earth constructed eons ago by the mysterious Vault Builders—explore its alien landscape & undermine the inhuman forces Can the heroes fight their way past the Ironfang Legion’s greatest leaders & confront General Azaersi before she activates her ultimate weapon A doomsday device that will wipe out not only Nirmathas but the surrounding nations as well?“ Vault of the Iron Citadel” is a Pathfinder Roleplaying Game adventure for 16th-level characters Ideas for further adventures expanding on the consequences of the Ironfang Invasion campaign an examination of the secrets & legacies of the mythic Vault Builders & a selection of new monsters round out this volume of the Pathfinder Adventure Path! Each monthly full-color softcover Pathfinder Adventure Path volume contains an in-depth adventure scenario stats for several new monsters & support articles meant to give Game Masters additional material to expand their campaign Pathfinder Adventure Path volumes use the Open Game License & work with both the Pathfinder RPG & the world’s oldest fantasy RPG