The twisted Egreth Forest, home of the night gaunts, today surrounds Egreth Castle and is the sight of several noteable historical events:

When Entharion the Wise abandoned his position in the Quendoran army before the founding of his kingdom, he receded into temporary isolation within Egreth Forest. He emerged in 0 GUE.

In 406 Yoruk built himself a modest cottage in the forests of Egreth where he lived out the rest of his natural life as a hermit where he would behind the workings of what is today known as the “Books of Saint Yoruk.”

Under the command of Pseudo-Duncanthrax in 660 GUE, portions of Largoneth Castle were moved to Egreth.

SOURCE(S): Zork Quest II, Zork: Grand Inquisitor (official strategy guide)