Few have ever seen the incomprehensible entities known as Trench Dwellers, but their lethal biomechanical machines remain, guardians of a long-forgotten empire.
In the dawning of time, a mighty civilization, mystical and alien, flourished in the oceanÃ¢??s unseen depths. Their day has passed, but their hidden metropoli linger on.
Pirates' many bejeweled rings and piercings actually had a practical purpose - when the pirate or sailor died, the rings could be taken off as payment for a proper burial, saving him from a watery grave. This could be tied into regional culture, or made into a quest (The Pirate's Lost Rings, etc.). Also gives treasure-seeking divers another thing to look for besides crusty old chests.