Hydraxion

Somewhere near the center of the Buccaneer Archipelago is the legendary undersea city of Hydraxion.

The deeps of Pearl hold a wondrous city with thousands of chests from sunken ships. The place is alien. It was built by tritons and marids and met to serve as a hold of Poseidon.

- pirate tale, "The Gilded Halls of Hydraxion"

Hydraxion is more tall tale than fact. Strangely enough, information on this mysterious place was found in the kuo-toa city of Shoglomph. The sole survivor of the adventuring band, Sons of Drog, managed to get this information back to civilization before expiring and soon turning into a kuo-toa tadpole.

The jade rune plaques of the kuo-toa described Hydraxion as a coral city, with the ability to move about the seas, creating air pockets for visitors or prisoners. The riches of the place are said to be chests of orkulten pearls and precious items of the depths, like luminant coral.