Essentially it's a small valley with a number of locations, though even calling them mini-dungeons would be a stretch. It seems that the valley has a magic tree and this magic tree was worshiped by followers of a fertility deity (Kishar). They lived there for a while until an evil magic-user came in and took over the valley, corrupting the tree and using it to create magical beasties. But the priestesses recuited an army of heroes who defeated them, but all died in the process (and despite being D&D, didn't have access to raise dead for some reason), leaving the valley more or less deserted and open for the remaning monsters people to slowly fill the power vacuum.
