I have had a dragon roll for which eel (freshwater?) is the primary ingredient. They aren't bad, but I admit it feels a little weird at first. Same feeling about mussels. And caviar.
Unagi is the bomb. And mussels, yes! And, I've never had caviar. How is it different than roe? I really love orangy red roe on may different rolls. I could eat that by itself.
Watch the very first Godzilla movie ever made. Understand how Godzilla was created, what gives him his power, and you should be able to tie it all together.