From the introduction:
This sourcebook features information on the Lost City of Grynix and the Dungeons of Grynix. The backgrounds of both areas are given, along with a history of how they came to be the places they are today.
In brief, some 3,000 years ago, a group of adventurers founded the city of Grynix on high principles and lofty ideals. The people of Eranon came to know Grynix as not only a wealthy metropolis, but also as a model for unity among the races. The city’s founders also designed and built extensive underground structures beneath Grynix; these were intended to hold prisoners and treasures, and to shelter innocents in times of war. Unfortunately, these "dungeons" reached the edge of the Dark Sprawl, not far from a Druegarn outpost of considerable size.
In 2274, the dark elves invaded Grynix from below, swiftly conquering a city that had been a symbol of the free races. Although the Druegarn were eventually defeated, Grynix was razed in the process. The city was lost and its dungeons all but forgotten for a time.
When the Druegarn took the city, many people evacuated to the relative safety of the dungeons. But, unfortunately for them, no rescue ever came, and several other reasons prevented these escapees from returning to the surface. Thus, for more than two millennia, the survivors and their descendants have lived and died beneath the ruins of Grynix, closed off from the rest of the world, in a set of complexes they know as Lower Grynix. Even now, the descendants of Grynix struggle for existence beneath the ground, their memories of the surface world growing ever dimmer, and the history of the city above becoming the stuff of legends.