Gary Gygax’s Castle Zagyg’s Upper Works: Gary Gygax’s Yggsburgh

A strange cloud lifts just west of the Urt River, revealing a place of legend, a monument of dread, known to the ancients as Castle Zagyg! But who constructed this mysterious place and had it enshrouded in the mists of legend? Certainly this is no ordinary invitation to adventure, but one so ancient that the treasures and magic within its catacombs and hallways must be those made by the gods themselves, for who else could contrive such a monument but a mad deity?