Dungeon Master Guide to Ramulia
From the introduction:
Steeped in mystery and tragedy Ramulia is a land that has been lost to civilization for almost 400 years. Many attempts have been made to settle this rich land, from small frontier towns to large defended outposts, but all have been abandoned due to a combination of monsters, invasions and the constant damage caused by the frequent earthquakes that plague the landscape. Once a great flat plane of forests Ramulia is now scarred deeply by the great earthquake that tore it in half, jagged knife like mountains stick up from the ground and whole wetlands have been submerged underground to create underground caverns ripe for monsters. The country's main geographical feature today is the Scar of Lenwë, a massive crevice with seemingly no bottom that splits the country in half.
Recently King Alred has made his claim on the country by building his capital of Dalmill on the site of a small successful village in an otherwise hostile landscape.