It`s not 100% sure to have all unit types in every game, i played game with only 3 red dragons available in it and game with no demons, seen comments from ppl thay had no demonesses in their game , or some other unit at all in whole game world. So maybe in you`re game there are no lake fairies
Tough luck man, try finishing it with some other build.
If you can figure out how this mod works, try using -dev commands :
http://forum.1cpublishing.eu/showthread.php?t=11759 Good luck