With an army of their own, the heroes finally wage war against the Ironfang Legion! To end the hobgoblin threat once and 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, and undermine the inhuman forces. Can the heroes fight their way past the Ironfang Legion`s greatest leaders and 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? A Pathfinder Roleplaying Game adventure for 16th-level characters, Vault of the Iron Citadel serves as the climactic conclusion to the Ironfang Invasion Adventure Path. Roleplaying Game adventure for 14th-level characters.