From the back cover:
"From his hideous throne in the wretched gloom of Dorakaa, Iuz the Old, Lord of Pain, stretches his bony hand across the Flanaess. Since the signing of the Pact of Greyhawk, his empire of tyranny and suffering is secure - at least for a time. None of the lands of good and hope are strong enough to threaten him. Iuz surveys his domain and cackles gleefully. He has added much to his holdings, but he is not yet content."
This sourcebook details the many lands Iuz controls; his dark priests and their magic; Iuz's fiendish allies from the Abyss; his marauding humanoid armies and raiders; and much, much more. These are lands of ineffable evil, a beacon for adventurers seeking glory within their perilous borders. Servants of good, prepare your weapons and ready your spells, for there are no challenges greater in all the Flanaess than those of the Lands of Iuz.