An interesting little niche in wuxia seems to be the mysterious "island" organizations. They're kind of like semi-literal representations of other-worldly beings who operate outside of the general wulin population and whose members usually far outclass the norm in terms of martial arts.
How many different island organizations come to mind and which would you consider to be the strongest? Off the the top of my head I can recall ...
Gallant Island
Gong Jiu's Island