WGS1: Five Shall Be One
Five Shall Be One is a second-edition module for Greyhawk, whose residents have no idea what's coming. It is tagged WGS1, a portmanteau of the WG and S lines, in part to evoke S4: Lost Caverns of Tsojcanth and WG4: Forgotten Temple of Tharizdun.
Lorraine Williams commissioned this in her bid to tear apart everything Gygax and the 1970s-80s generation ever worked for. Carl Lynwood Sargent wrote this one, sort of a job-interview for From The Ashes.
In it the Suloise barbarians of the far northeast unite under their god come to Earth, Vatun. They wreak havoc. SURPRISE Vatun is an agent of Iuz. There's more in the WGS line, for all anyone cares, but it's all to culminate in the Greyhawk Wars.
WGS1 is, therefore, one of those tiresome modules done to force a change in canon, like Dead Gods. This means the players' characters are patsies who cannot change the outcome. You may as well read a book so why buy the railroad-ticket? Once 1e Greyhawk fans figured this out, they didn't want to play it either.