Creatures

About
The term "creatures" is used to describe the entities that commonly lurk in levels 5 and lower of the sewers. Examples can be The Light Man, Grumpy Gargle and others. Origins of these entities are unknown and were discovered somewhere around 1100-1200 AD although many paintings, books and folklore suggest it was at least before 1050 AD. The first solid record that referenced these entities is a book written in 1237 AD called "Legend of The Light Man". The book talks about The Light Man, which is a famous example of creatures. Not only is this solid evidence of creatures existing at this time, but the book title calling the stories a "legend" means that it was likely somewhat old and passed down word to mouth, and supports it's possible beginning of existence during 1100-1200 AD.