Land of Iuz

The land of Iuz has supposedly been ruled by Iuz for ages longer than any human, but very little direct information comes out of Iuz. Is Iuz a human or was once human? Or is Iuz a title that gets passed to each ruler? What is known is that their land stretchs from the Howling Hills south to the Lake of Whyestil and between Dulsi and Opicm Rivers. It's rumored that all manners of wickedness exists within these borders, but the only persons to come out of there worship this leader Iuz with a zeal that's beyond rationality. 
Rumors do exist that for a time mad Zagyg held Iuz and nine other demigods trapped below Greyhawk Castle, but there was an event there in 570 CY that also supposedly released these foul deities.