All the levels in Witch were built using Witch's custom level editor, WitchED. WitchED is basically a compositor, allowing you to place prefabricated meshes, and also a tile editor, allowing you to change the functions of specific tiles.

WitchED then exports an xml file containing the locations and properties of the tiles (for example, where a player start location or a cauldron is), and also whether or not they are passable.