The Nameless Book is a magical tome with dark magic and various mystical spells including the power to summon the a race of evil extradimensional monsters called the Old Ones and it plays a major role in the episode "Russian About" of The Real Ghostbusters cartoon series. The book is a relic from a time when the Old Ones ruled Earth, a book so powerful, so ancient, and full of sorcery that no one can say its true name or terrible things would happen.
During a paranormal conference, the Nameless Book was stolen from a Soviet institute's collection by Vladimir Pavel Maximov and Dmitri Smerdyakov. In order to distract the authorities, they pinned the theft on the Ghostbusters. In the confusion, they took the book to the Old One Cult, an evil cult organization they were members of, and began to cast a spell from it. The cult was taken to the Temple of the Old One where the book awakened the Old One. The book was never seen again after the Ghostbusters defeated the Old One.