On this page, you can find a bunch of extra content for the game. This includes things that didn't make it into the main rest of the site such as other events and character stories and small details, as well as fanworks that are pretty great!
While this site covers all the main content of the game, there are still some other pieces of content that it doesn't go into such as other events and the like.
In addition, characters from the game Persona 5 were added with an event and are playable. They are the only characters in the game who are playable who were not from the Drakengard franchise. You can find their info on the NieR Wiki in the Crossover Characters category.