Iuz was conceived around 460 CY, shortly after his mother Iggwilv imprisoned the demon lord Graz’zt. He first came to prominence in 479 CY, when the handsome youth gained control of a petty fief in the Howling Hills. Ostensibly beholden to Furyondy, in practice it was independent. It had been left to Iuz upon the death of his “father,” a human ruler who had supposedly claimed that Iuz was his son. Almost immediately, Iuz transformed his estate into an armed camp, and began cultivating alliances with the other local lords. Using cunning and guile, Iuz manipulated his “allies” against one another and against stronger opponents, weakening all of the cambion’s rivals. Slowly Iuz’s forces increased in size as humans and orcs gathered under the the banner of the Child of the Evil One. The humans cared little for the orcs, but they liked how their opponents feared the orcish shock troops. Goblins, similarly, began rallying to his cause as well. By 480 CY, Iuz had earned the title Lord of Pain as his conquest began against his weakened neighbors. The atrocities he committed during these early campaigns made it clear to all who witnessed those battles that whoever his parents were, Iuz certainly had no humanity. Before long, Iuz controlled three neighboring fiefs in addition to his original one. King Avras III of Furyondy called his southern nobles for aid against the warlike upstart, but the nation fell into internal squabbling and in the end did nothing to restrain the cambion’s ambitions.
Iuz’s true mother Iggwilv was conquering Perrenland at the same time, but she found time to aid her son with her magic. Iuz, as a marquis cambion, had magic of his own that he used to great effect in intimidating his followers and enemies. Soon Iuz’s capital of Dorakaa had become a charnel house, with a road made from the skulls of the young leader’s enemies leading up to it. Watchtowers built along the road by chained slaves were used to burn the the living flesh of prisoners en masse. By 500 CY, Iuz had conquered the westernmost Bandit Kingdoms and named the city of Molag his “summer capital.” As far away as the Principality of Ulek, contingency plans were drawn up in case Iuz should invade.
In 491, Iuz was present at his mother’s court when his father Graz’zt made his bid for freedom. Iggwilv had, at Graz’zt’s suggestion, decided to use her pet fiend Tsojcanth to seal an ever-growing hole leading to the Abyss. Tsojcanth rebelled unexpectedly, and as Iggwilv was recovering from his attack, Graz’zt attacked as well. Caught between the uncontrolled magic of both his parents, Iuz was inadvertently split into his human and fiendish halves. From then on, Iuz’s once-handsome visage resembled a withered old manikin or a bloated, bestial-faced demon. He took the former form when he wished to put his supplicants at ease, and the latter when he wished to intimidate his foes.
Although Graz’zt was ultimately banished, Iggwilv’s powers were exhausted by the melee, and she retreated to other worlds to recover. Without his mother’s magic, The progress of Iuz’s empire slowed, though it did not stop.
Iuz began the process of transforming himself into a deity, gathering powerful wizards or extra-planar beings beneath the Soul Husks Caverns in the Howling Hills. With horrific magics, he drained them of their power, incorporating them into his own being. He also cultivated an alliance with Zuggtmoy, the demon queen of fungi, laying the foundations of what would become the Temple of Elemental Evil.
Then, in 505 CY, Iuz was captured by the wizard Zagig Yragerne and his allies. Along with eight other demigods, he was incarcerated in Zagig’s Godtrap beneath Castle Greyhawk until released by Lord Robilar in 570 CY. In the cambion’s absence, several “false Iuzs”—illusionists, demons, and demodands with delusions of grandeur—began dividing the empire between them. Further south, the landholders of Iuz’s former lands dedicated themselves to the worship of Nerull, Anthraxus, and the Lords of the Nine.
In the meantime, the orcs of the northlands had named him the Old One, and their worship helped increase the demigod’s power. Loyal and opportunistic humans joined the cult, and soon some were rewarded with clerical powers in spite of their patron’s imprisonment. Uneasy with the growth of Iuz’s faith, the southerners joined together to form the Horned Society, making Molag their capital.
In the next half-century, the cultists of the imprisoned Iuz had eliminated their rivals in Dorakaa and established a tenuous peace with the Horned Society to the south. In 570, Robilar, his orcish henchman Quij, and the priest Riggby ventured to the Godtrap at Mordenkainen’s urging. Using magics Mordenkainen had given them, they freed Iuz with the intent of slaying him. Tenser, Bigby, and Neb Retnar showed up shortly thereafter, and a six-against-one melee ensued. Bigby might have crushed the weakened Iuz to death using his famed Hand spells, but Iuz’s magic lashed back at him, leaving Riggby catatonic for days and turning Neb Retnar to evil.
Iuz returned to Dorakaa, slaying impostors, dissidents, and those whose bodies exploded particularly entertainingly, their skulls adding to Iuz’s grisly road. Iuz established himself as a living god, and the Oerth trembled.
Though aware of the return of his nation’s old foe, King Belvor IV of Furyondy ignored it at first, concentrating on uniting the quarreling factions within his own country. Iuz, for his part, spent some time ensuring he had absolute mastery of his kingdom before making his next move.
That move came in 582 CY, when a band of barbarian heroes—Stumred Barduran, Baern Barraeth, Fenestir “Swifthand” Galander, Ingrid Hashandir, Sabrala Starbreaker, and Helden Stormfist—reunited the legendary Blades of Corusk. The mage Karasten Meldraith arranged them in an alternating pattern, uncovering a spell hidden in the runes of the blades. Before he could finish reading the spell that would awaken the lost god Vatun, however, Iuz manifested in Vatun’s guise, scattering the blades to the four corners of the world. The whole episode had been a set-up by the clever Fiend of the North. With a guileful tongue, Iuz convinced the rulers of the Fruztii, Schnai, and Cruski, and the raiders of the Hold of Stonefist, that he was the Great God returned. At his direction, the Fists invaded the Duchy of Tenh, decimating its armies and driving the Duke and Duchess to exile in the County of Urnst.
The alliance did not last long. The Suloise barbarians resisted “Vatun’s” orders to invade the Bone March and Ratik. Eventually they refused to believe Iuz was their Great God at all, but the damage had already been done: Stonefist was firmly allied to Iuz’s cause.
Iuz returned to Dorakaa in 583. During his absence, his chaotic empire had already begun to disintegrate. Iuz responded by executing the exiled Furyondian nobles who had been his vassals and replacing them with things from the Abyss—nabassu, cambions, vrocks, hezrou, and mariliths. His mother, using her Nethertome, summoned many demons to bolster her son’s armies, but this resource soon ended when she attempted for the second time to summon Graz’zt himself. This time Graz’zt was prepared for her arts, arriving in her protective circle with a device that disrupted it. Smiling wickedly, Graz’zt seized the shocked Mother of Witches and dragged her back to his Abyssal realm to torment her at his leisure. Iuz continued to gate in summoned demons, but from then on he did so only with the permission of his demon lord allies Pazuzu and Graz’zt. Graz’zt had the upper hand in these dealings, holding Iuz’s mother hostage as he did. Yet Iuz knew that Iggwilv craved only her own power, and might well have turned against him had she been free, so his feelings on the matter were complex. Iuz dealt regularly with Lolth as well, though they made no formal alliance. Lolth’s ambassador to Iuz’s court, Eclavdra, served Lolth and Graz’zt simultaneously at the time, with all parties involved being well aware of this.
On the night of the Blood Moon Festival of that year, Iuz struck against the Hierarchs of the Horned Society, his agents slaughtering all but two of them (who were away at the time) and adding the Horned Lands back to his growing empire. With the hobgoblin warriors of the former Horned Society bolstering his own troops, Iuz swept into the Shield Lands in the Flocktime of the following year. Perhaps the Shield Lands could have resisted, but they refused to allow the Furyondians to aid them, fearing re-annexation by their former Furyondian rulers. The Shield Lands were conquered, and Iuz moved on to the borders of Furyondy. Worse yet for the forces of Good, Iuz had managed to acquire an alliance with Ket, who had long born a grudge against the peoples of the Sheldomar Valley. With Ket flanking them on one side and Iuz attacking on another, the defenders were hard pressed to resist. At the same time, Lolth manipulated hordes of giants into invading Geoff and Sterich, distracting the peoples of the Sheldomar still further.
Somehow, despite losing much of its northern territories and the Vesve, Furyondy managed to hold. With tens of thousands of his troops slain, Iuz agreed to the sign on to the Pact of Greyhawk. He would consolidate his gains for a time before striking anew.