Black Report is a record of crimes against the descendants of the Shadow by the Hunter Association. The Shadow was the Association's secret operation squad which was annihilated by the chairman Netero as they were beginning to make use of On. The survivors, Shura, Gaki and Rengoku revived the leader of Shadow, Jed, using their hatred, to avenge the deaths of all of the members. The four then rose to action against the Association to disclose the Black Report to the public.
The Black Report is mentioned in the movie: Hunter × Hunter: The Last Mission