Artist note: You'll notice that she also looks similar to the
Nightwalker posted on the first page. This is because she is infact a female variant of that same monster.
You see, the male nightwalkers kill humans and harvest their organs, not just for collection purposes but, also as a way to attract the females to them. Female Nightwalkers like human insides, they find them tasty and arousing to play with. Thusly, the nightwalker who has the largest collection of innards gets the most attention from the girls! \o/
Nightwalkers are usually found in forests and only come out during nocturnal hours (obviously enough), they despise Light and try to avoid areas that are bright or have alot of light sources within it. The number of Nightwalkers seems to dramatically increase on nights of a New Moon, conversely, less are known to appear on nights of a Full Moon.