The PCs are sent after the surviving Cavewrights, who are hidden in a ruined yuan-ti stronghold under the peak of Shatterhorn. New feats include contagious paralysis, improved fiendish servant, and improved paralysis (the paralysis feats are from Libris Mortis); new spells including shadow dagger and shadow puppeteer; and new magic items include the lesser amulet of the planes, blackstone rune, ring of thirteen, and serpent's eye (the rune is from the Fiend Folio). Part of the Shackled City Adventure Path.