The archdemons mentioned in the Necromonicon were in force before the Chaldeans existed even, from places the modern idea of "hell" or "hades" or "satan" were even conceived by Man. Many demons are still unknown, and so powerful it beggars belief. Few even know about these ancient demonic realms - one, as this video describes - was the "Mad Arab" Abdul Alhazred who resided in ancient Mesopotamia around 740AD, who perished after gaining the knowledge and visiting places few, if any, have ever visited, let alone even known about. The "mad Arab" put much of what he had experienced and knew in a record, some of which is [sometimes loosely] represented in this representation of the Necromonicon. Few can even cast their eyes upon the real "book", of which there are few translations in eg. Latin etc., now kept in closed rooms in very few locations. It is said even to read what is in this tome can bring death, or severe debilitation to the reader. So be it.
more: The Necronomicon - All You Need to Know About the Worlds Most Dangerous Book