As already stated, Tralodren isn't just about one world, but a whole cosmos encompassing the various realms and planes around it. The world itself is about the size of earth, with more water than land covering its surface. The land it does have is a collection of islands and smaller continents that were formed, in part, by the breakup of a larger supercontinent nearly 7,000 years ago. This event also ringed the plant's equator with a formidable barrier called, The Boiling Sea, which has kept the two hemispheres from interacting with each other ever since.
The world is further protected from incursions via other planes and realms by a divinely crafted barrier erected when the planet was first created.