Metamor Keep (MK)
Metamor Keep (MK for short) is a fairly typical fantasy setting in which cultural and technological development are more-or-less medieval, magick is strong and reasonably common, and there are a number of very active deities. As per usual in such settings, Good and Evil are not only well-defined, but also have obvious national 'avatars'. The setting is named after a strategically located castle which is a vital part of the military defense of the Good peoples against the forces of Evil. The Keep itself has no fixed floor plan, as it's inhabited by a powerful (and benevolent) spirit which tends to relocate the internal walls and such without notice.
One day, the local forces of Evil mounted a serious attack on the Keep -- including a set of curses which ought to have completely neutralized the defenders, transforming each one into either a helpless baby, a grossly oversexed member of the opposite sex, or a dumb animal. Fortunately, the Keep's own mages were able to blunt the force of this magickal assault. While the Evil curses failed to achieve their intended results, they were not fully neutralized, and their effect is felt even to this day. Ever since that battle, any person who remains within a day's ride of the Keep for more than 10-14 days will fall victim to a weakened version of one of the three curses. Some become children (but not babies); others become normal members of the opposite sex (without being carnally obsessed bimbos); still others become human/animal hybrid creatures (who usually retain the intelligence, manipulatory capacity, voice, etc, of their former body).
Go here for an extensive, well-maintained archive which contains hundreds of MK stories, plus a great deal of helpful data (FAQs, maps of the Metamor valley & castle, etc).
This setting was created by Copernicus, who has delegated to Christian O'Kane the power/responsibility of declaring which stories or concepts are canonical for MK.