I have been thinking recently about how great it is to have some redundancy in the encyclopedia. Some monsters are similar to others, there are categories of monsters with similar enough traits but each member has enough distinguishing features to make them different. Like having 7 types of lamias. And in theory there isn't any problem with having more monsters living in northern/snowy/mountainous regions, the better to ensure no one dies out there. But as far us readers are concerned, 4 different species of monsters who are ice spirits given female form feels like a bit much. I almost want to know what a fifth ice mamono would look like. I also feel like an encyclopedia in which there were one fewer of these four mamono wouldn't be missing much.