World 40 is a largely unknown world. You can get here from world 39, but the exact location of the portal isn't known. Lasu managed to get here from world 34 during a worldly dislocation, but that portal was closed moments later. She noted upon arrival that it didn't smell of chemicals or fumes. She also came across an odd breed of monsters, "looking something like a mutated panther".
Other than that it's a nice world with great variation in demonic life and decent cities.