An interesting question came up on Canonfire. Why would Mordenkainen allow Rary to continue to consolidate his Empire of the Bright Lands without interference?
To recap: in the World of Greyhawk, Mordenkainen is the leader of the Circle of Eight, a group of wizard Illuminati. They pull the magical and political strings behind the scenes in order to preserve a balance of power across the continent of The Flanaess, ensuring neither the forces of Good nor Evil gain the upper hand. Mordenkainen himself, furthermore, holds to an arcane philosophy known as the Balance, a True Neutral view of the cosmos in which, in order for magic to flow unhindered, a balance must exist between the metaphysical forces that make up the multiverse (see also Mordenkainen's Tome of Foes or my own thoughts on the matter). Rary and Tenser are both former members of the Circle, Rary having betrayed the Circle and murdered Tenser. After Rary's betrayal, he fled to the Bright Desert south of the City of Greyhawk to set up his own domain. Tenser meanwhile, was brought back to life by a party of adventurers to pursue the cause of Good.
So the three wizards no longer hold allegiance to one another, one is devoted to Good, one to Evil, one to Neutrality. Why is it that there is no great magical battle between two or even all three wizards?
The answer, I guess, lies in motive. Mordenkainen is a powerful archmage but not as powerful as Rary, who has always been described as surpassing Mordenkainen in arcane might. Sure, Mordenkainen can manipulate events and entire adventuring parties to oppose Rary, but for the moment, Rary serves his purposes. In Rary the Traitor, is is stated that the self-styled Emperor of the Bright Lands seeks to find an artifact known as the Scorpion Crown. Later in the Living Greyhawk-campaign, this becomes an entire quest-line. Rary seeks to find the Crown in order to destroy it and return the Bright Desert to a green land. Furthermore, the Crown is a link to the Dark God Tharizdun, who seeks to unravel magic and unmake the multiverse - a goal that Mordenkainen opposes. Finding and destroying the Scorpion Crown weakens Tharizdun's links to Oerth. Therefore, Mordenkainen allows Rary to pursue these ends.
Tenser, meanwhile, knows that Rary is more powerful and better supported than he is. Rary controls various desert tribes and Paynim nomads. He prefers to work through underlings, like his paladin ally Karistyne. In the adventure arc "Blight on Bright Sands", he does just that - let Karistyne hire adventurers to oppose Rary and destroy the means to unmake the Scorpion Crown.
It is interesting to consider the implications of three archmages playing a game of cosmic, arcane chess against each other and with what motives and what this means for adventures in the World of Greyhawk.
