Setting created by Thunderhead Games / Mystic Eye Games
From the now defunct website:
"Nearly 200 years after its founding, Bluffside looks over the bay below, confident in its power; power brought about from adamantine. The otherworldly metal permeates the surrounding mountains, brought to the world nearly 200,000 years ago by an asteroid that tore a portal between the prime material plane and the plane of shadow and nearly annihilated the world's civilizations. The ruins here are alive with the ghosts of the ancients.
Bluffside uses Sordadon, a city floating in the bay below, to dominate sea trade in the area. The connection between Bluffside and Sordadon is through Undercity, a vast series of underground passageways that extend off into the unknown. From temples to mining to adventuring, Bluffside has something for every adventurer.
Bluffside is the first in our line of truly modular sourcebooks. Designed to be easily dropped into any middle fantasy setting, Bluffside promises to become the center of your campaign. Over 100 places of interest (POI), along with corresponding NPCs and adventure hooks, give life to the city and allow the GM to jump right in."
From Troll Lord Games:
Civilization is still picking up the pieces following an asteroid strike two hundred thousand years ago. The epicenter? Bluffside. Only 208 years after its rediscovery, Bluffside is a boom town boasting the most precious metal in the known world - adamantine. From the ancient ruins of Sem La Vah, to the vast Undercity, to the floating port of Sordadon, Bluffside: City on the Edge promises to become the home port for thousands of adventurers. Used as a stand alone city, or combined with other sourcebooks, thereby creating a modular world one great area at a time.