I just have something of mild interest to note:
I noticed that in reading the Field Guide entry concerning how to access the secret level, the method was incredibly easier than the version I encountered. I had no idea all you had to do was kill the frogs.
The way I heard about a level was from a friend who said you could only get to the level by killing Rurik JUST as he crosses the threshhold of the gates into the town. He told me I would know the trick worked when the computer-controlled troops outside the city would move inside the city as if I had won, while the villagers would still say "you killed rurik! you bastards!" It took me quite a few tries, but, if I remember correctly, that WAS the way I obtained access to the secret level.
I'm wondering, can anyone verify this? This is the only method in my recollection of getting to the secret level for a year or so, before I read the field guide last week.