From the introduction:
A campaign, or plot line, can be as short as an afternoon or as long as several years if you like; the beauty of pen and paper is that the players have all the control.
This is the beauty of Mod. This is a game that has taken the concept of player control to the limit.
Unlike most pen and paper games, which limit players by supplying lists of spells and techniques and by making players define their characters by classes, Mod is all about freedom. In this game, you can choose your own path, make your own spells, and design your own combat techniques.