TerrainWML

the toplevel [terrain] tag

the [terrain] tag describes a terrain in WML. Terrains are usually described in the terrain.cfg file

the [terrain] tag has the following keys and subtags

image an image used for this terrain in the map editor
symbol_image appears to work the same as image - clarification is needed
adjacent_image a prefix for adjacent terrain images. they will be postfixed with the orientation of the border to give the image name that will be used for the border terrain
name the name of the terrain
char the character used to represent this terrain in maps and scenarios
aliasof characters representing terrains that this terrain will be an alias of. (i.e. Units' defense and movement on this terrain is equal to their best defense/movement on one of these aliases.) (All terrains are aliases of themselves.)
unit_height_adjust how much the unit graphic should be moved up or down when on that terrain
submerge float, between 0 and 1: stems how much of the unit graphic should be submerged by the terrain
no_overlay whether this terrain should be overwritten by other terrain's borders; 'no_overlay=true' terrains are not overwritten.
light signed value. this will modified local light level on that hex by that amount for gameplay
heals if set to true a unit on that terrain will be healed at the start of every turn
gives_income if set to true, this terrain will give income every turn when flagged as if it were a village
recruit_onto if set to true, it is possible to recruit or recall on that terrain
recruit_from if set to true it is possible to recruit when a unit that can recruit is on that terrain