so by level you mean "zone" right ?
How is elevations handle ?
Elevation is handled in two ways.
First is by materials and transitions. Example, you have a ground material, a high material and a low material, the transitions will form walls between them; example use as continent edges, or the slope from desert to forest in matis continent.
Second there is a very low resolution heightmap which is used to offset the terrain blocks in height so you can create deep slopes and such; example use is the large downward slope part when going from north to south of matis continent.
In addition there's also maps to handle fog color and depht settings, rain settings, etc, depending on player position in the landscape.