Its a great name for a pirate city, and that cryptic arch is just pure nifty. So could someone please list me the books I'd need to get as complete a picture of Riddleport as I can while I scour the internet for other piratey goodness?
Second Darkness campaign starts off in Riddleport. So check out the Players Guide and adventure Path #13 Shadow in the Sky. They provide a wealth of info on Riddleport, though I must admit there seems to be a lacking of the general history.