Greyhawk Adventures (1988)
For almost three years after the departure of Gygax from TSR, no new material about Greyhawk was published other than the "joke" adventure module Castle Greyhawk. In 1988 Greyhawk Adventures by Jim Ward appeared, the thirteenth and final hardcover book published for the 1st edition Advanced Dungeons & Dragons rules. The contents were designed to give Dungeon Masters ideas and play opportunities unique to the Greyhawk world, and included six plot outlines that could be inserted into a Greyhawk campaign. One of these was "Csipros Erd—Geysers of Death", set in the borderlands of Ket: 65 years before (510 CY), the young Lord of Polvar, Sandor the Headstrong, pursued a band of orcs carrying a great store of treasure into the Yatil Mountains. There the Ketites cornered the orcs in a geyser-filled valley, but suddenly orcs and humans alike were overcome by a mysterious vapour issuing from the geysers. The only survivors were Sandor and a few men who had been observing from a nearby hilltop. Sandor and his men returned to Ket for reinforcements, disappeared back into the Yatils to recover the treasure, and were never seen again. To common knowledge, the geyser-filled valley and its lost treasure have not been re-discovered since.
This was the first mention of "Polvar" in published material, and while it was not clear whether Polvar was a city or a province, in later editions of the setting, it would become both.
Read more about this topic: Ket (Greyhawk)