An answer to most of the obvious questions about the game (including the question in the OP) can be found in the FAQ.
Dominions 3 FAQ thread -
http://forum.shrapnelgames.com/showthread.php?t=33869
The Wiki is also a good source of answers, and is slowly expanding due to the efforts of the few dedicated soles who work on it. (the answer to the original question can be found in the Wiki as well)
Dominions 3 Wiki -
http://dom3.servegame.com/wiki/Main_Page