Rob's Greyhawk Undying Wyrms
Multi-layered sub-terranean complex containing a lot of dodginess which needs dealing with, much of which is behind doors which cannot be opened without the correct keys. These keys are hard to find.
Trap for creatures, including fallen angels, it is his main temple in the world. Gods of good led by a feathered woman, defeated him and sundered his sword. It was made from the fang of the 1 TRUE EVIL God (Big T?)
It was were Orcus had his first and last footprint on Oerth
One of three places where Hellring could have been destroyed (see Pelur Keep)