At ZBrushCentral there is a guy (Ryan Lim), who actually worked on this game, creating some of the creatures with ZBrush with high poly mesh (later decimated to low poly mesh for game speed optimization) ... here is the link (i'm not sure, if you will be able to view the added images, maybe needs registration):

http://www.zbrushcentral.com/showthread.php?t=077034