Robilar and the Nine Imprisoned Demi-gods: The freeing of Iuz and the other eight "demi-gods" imprisoned beneath Castle Greyhawk was instigated by Robilar, who released them (Robilar seems to like freeing things, being a free spirit himself!). This event occurred in the dungeons of Castle Greyhawk on a dungeon level known as the "Bottle City," which was a level created by E. Gary Gygax.
Robilar, who was 10th level at the time, entered the containment room, and viewed the nine imprisoned creatures mounted a top pedestals VERY carefully before deciding to deal with the many-handed one first (i.e. Hextor). Robilar decided to dispatch (singly) the toughest melee capable of the lot first, in case all nine were to animate simultaneously (the nine imprisoned were: Iuz, Ralishaz, Trithereon, Erythnul, Olidammara, Heironeous, Celestian, Hextor, and Obad-Hai). In the ensuing melee with Hextor, the other eight "demi-gods" were "accidentally" released, as loosing one seemed to have a domino effect. As the nine "demi-gods" turned their attentions toward destroying each other, Robilar executed a tactical withdrawal (i.e. he ran for his life) to lick his wounds.
Robilar later returned to the room to investigate. Before returning, he heard the sounds of a great battle occurring (which was another reason for returning to investigate). Upon re-entering the containment room, he saw that all of the pedestals were empty, with no beings in sight. All nine of the gods were loosed upon the world.
Many readers will recognize that the "nine demi-gods" released by Robilar were later to appear in published Greyhawk materials as both demi-gods and lesser gods. Rob explains this discrepancy as follows: "What I remember about the demi-gods is that there were nine that Robilar set free. Gary later referred to them as demi-gods, as I sought more information about them. They essentially disappeared into the World of Greyhawk wilderness, never to be heard from again until Gary rewrote them for the World of Greyhawk Campaign Setting (Second Edition, 1983). That Gary later referred to them as lesser gods is understandable. In reshaping something that originally appeared in 1972 in his actual campaign, name changes and/or designations appeared and disappeared. Gary was defining his world as well as presenting it for the consumers and fans alike, so this was natural. Upon publication of the campaign setting he had (and we all had) a firm placement (and understanding) of demi-, lesser- greater-, gods, etc. I will add that Gary seemed very pleased when Robilar loosed these creatures, and I was to find out why much later in the Temple of Elemental Evil!"
Robilar and the Temple of Elemental Evil: The Temple of Elemental Evil campaign was designed by Gary Gygax to introduce new players into the Greyhawk campaign. During this period, a lot was happening in Hommlet, as a whole new breed of Greyhawk adventurers rose in levels. But the Hommlet campaign was a beginning campaign and most of the characters involved were low level. They were scared to death to go near the Temple. After hearing of the happenings in the Hommlet area, Robilar finally decided to investigate the Temple himself.
In CY 575, Robilar traveled with his henchmen Quij and Otto the Mage to the Temple of Elemental Evil. Robilar traveled on his flying carpet and Quij and Otto followed on griffons. Robilar entered the temple complex with Otto, leaving Quij behind to guard the griffons and flying carpet. While other adventurers raided the temple and then withdrew, Robilar entered the temple and fought his way through it. For two days he slew all he encountered. Eventually Robilar freed the demoness Zuggtmoy, who was imprisoned beneath the temple complex. (Artifact of Evil states that Mordenkainen was present and purposefully assisted in "freeing" Zuggtmoy in some scheme designed to preserve the Balance. This was a later literary addition by E. Gary Gygax.) Why did Robilar free Zuggtmoy? Robilar purposefully released the demoness, because too much good was going on around the place. In a manner, to balance the proceedings.
Alerted by the "freeing" of the demoness, a Force of Good rushed to the temple complex in an attempt to recapture the demoness and to punish her liberators. Tenser and his associates arrived, with Burne, Rufus, Otis and a great force of elves, paladins and unicorns. Upon seeing the destruction of her temple complex and the gathering Force of Good, Zuggtmoy departed in great haste. Robilar and Otto fled back to his castle, with the Force of Good in hot pursuit. The druid Jaroo, in falcon form, followed Robilar and Otto over 200 miles back to Robilar's castle. After they were informed of his whereabouts, the good war party eventually rallied outside of Robilar's castle. Robilar and Otto abandoned the castle and it fell to the Forces of Good.