One misstep traps Gregory in a fantastic prehistoric cavern populated with fierce Jurassic relicts and a society of ancient nomads who think he's a god. One misstep changes Gregory's outing into a terrifying fight for survival in a cavern that originated in Jurassic time. He discovers a civilization whose savage ancestors were trapped inside by a glacier 30,000 years ago. The people are diminished in size by their lengthy confinement and have come to believe the cavern is the extent of the universe. Gregory encounters beautiful Valea, chained as a sacrifice to Mohk'wa, the Death God. She thinks Gregory is a giant god and fears she will again be sacrificed if she returns to Stonehaven without joining in fireseasoning rites with him. They meet Driggett, a gnomish man from Lower Rockworld who becomes Gregory's closest friend and ally. Together they battle the priests of the Bat God who perceive Gregory as a threat to their dominance. War ensues, pitting minions of the Bat God and their Crystal warriors against citizens of Rockworld. Mohk'was lurk in many of the halls, wreaking mayhem on all in their path. Through it all, Gregory searches for a way back to the outside world, one that may not exist.