Assault the Vault! For months, the merciless Ironfang Legion hasstruck out against humanity from its impenetrable, otherworldly Onyx Citadel!But now in possession of a key to this stronghold, the bold adventurers mustrally their allies, breach the barrier between worlds, tame an alien wilderness,and finally bring the fight to their hobgoblin conquerors! Can the heroes bestthe Legion's most devious commanders, including the unparalleled warrior-generalAzaersi, or will they fall as readily as their homeland before hobgoblinblades? This Pathfinder Adventure Pathvolume concludes theIronfang InvasionAdventure Pathand includes: * "Vault of the Onyx Citadel," aPathfinder adventure for 16th-level characters, by LarryWilhelm. * Suggestions for continuing thecampaign beyond the adventure's end, including a gazetteer of the Vault of theOnyx Citadel, by Crystal Frasier. * An ecology of the Vault Keepers andthe mythic Vault Builders, who together compose the xiomorn race, by Greg A.Vaughan. * Details on the powerfulxiomorn-crafted relics adventurers may find when exploring the Vault of the OnyxCitadel, by Tim Hitchcock. * A bestiary packed with elite IronfangLegion troops and denizens of the Plane of Earth, by Paris Crenshaw, KalervoOikarinen, and Larry Wilhelm.