When the background lore of a piece of media goes really deep. Sometimes used jokingly on small details the author has put in, but true deep lore consists of a variety of hints spread throughout the story that only dedicated fans will discover. These hints usually hold historical, philosophical, religious, and other metaphorical meaning.
Person1: Did anyone else notice the main character's weapon looks similar to that stick from the carving of an ancient Egyptian emperor?
Person2: deepest lore