This sentence might have originated from the plot of a novel or manga. In novels, characters often used similar self-praising words to enhance their mystery and appeal. However, such exaggerated methods did not necessarily bring good results. Sometimes, they were even annoying. There was no clear definition or source for the phrase "the darkest Journey to the West". This statement might just be a metaphor used to express the extreme darkness or strangeness of a certain work or plot. However, it does not represent the true nature of the work or the plot itself, so it cannot be judged solely by it.