From the back cover
Or, The Occasion Of a Visit Into The Underworld By Way of The Grand Entrance To The Ancient Dwarven Fortress of Thrumi`Zud:
ZH-01 is an adventure module for a party of five 1st through 3rd level adventurers and their henchmen. It has been exactingly designed to fit within almost any campaign milieu and to make running your players through it easy, providing just enough detail to spark your and your player’s imaginations into a wildfire of creative - collaborative - world-building.
SOMETHING brought down the mighty civilization. The sages say it was desperate invaders from below, escaping something even more horrible. Whatever it was, Thrumi`Zud was quickly overwhelmed and sealed, forgotten except in the stories of the old.
The vast riches of the fabled Dwarves must surely be hidden within its depths. Perhaps you will be the one to rediscover them.
Perhaps there are secrets better left unearthed. Horror lies within. You have been warned.