Iuz is the demigod of Deceit, Evil, Oppression, Pain, and Wickedness. Iuz is variously called "the Old One" and "Old Wicked," among other titles. Unlike most Greyhawk deities, Iuz makes his home on Oerth, where he rules a broad swath of the Flanaess known as the Empire of Iuz. His symbol is a grinning human skull, or a human skull with blood-red highlights.
Iuz has a fractured appearance, and is able to appear as a frail old man, or as a bloated, demonic being, which is his true form. The sight of his true form is enough to send whole armies scattering away, gripped in madness.
Iuz is the cambion (half-demon) child of the demon prince Graz'zt and Iggwilv, the so-called "Witch Queen of Perrenland." He is an ally, and sometimes lover of, Zuggtmoy, Demon Queen of Fungi, who keeps his soul amulet safe in her layer of the Abyss. From "blood-black Dorakaa," the City of Skulls, Iuz rules his empires. He has many armies across the Flanaess, and he even has demonic agents buried in the minds of many rulers across Greyhawk.
For now, Iuz bides his time since the Pact of Greyhawk, but soon he will strike again. The only question is whether the forces of the Flanaess can hold fast against his evil hordes.