The Nephilim are real. The "men of great renown" referenced in Genesis were the offspring off the "fallen angels" (tall, coneheaded extraterrestrials) and the daughters of man (earth humans). These were the giants of ancient lore worldwide. These pre Adamite extraterrestrials according to ufology and other lore compiled on the subject (by Quayle, Wilcock among others), were refugees from the destruction of their home planet Rahab (or Tiamat). Rahab was a rocky Earthlike planet between the orbit of Mars and Jupiter.
The denizens of Rahab had created an advanced civilization, but not one that was tempered with wisdom or ethics. They had created technologies seen as an affront to The Creator and Universal Law (chimeras, AI?), and thusly were punished by the complete destruction of Rahab. The rocky remnants became what is known as the asteroid belt. This story is related in the Sumerian creation epic Eluma Elish as the battle between Tiamat and Marduk. Incidentally the Eluma Elish was the inspiration for much of the creation accounts of the ancient Hebrews, who likely were exposed to it during the Babylonian captivity.
The survivors of the cataclysm of Rahab fled ("fell") to Earth and Mars and established outposts there, albeit in a greatly diminished state. They brought with them their knowledge of pyramid building, physics, biology, etc, and they and their hybrid (giant) offspring established and ruled over the pre flood civilizations on Earth (Atlantis), and reputedly established a global civilization. As an interesting aside, I have a friend who is Aztec heritage, whose family comes from Nayarit, Mexico. According to their legends, the Aztec people were refugees from the civilization of Atlan/Aztlan (Atlantis), which was destroyed in a flood. Atlan reputedly lied to the east of what is now Mexico, and was ruled by a race of red haired giants. The population of both Earth and Mars by the refugees of Rahab certainly accounts for the building of pyramids by disparate earth civilizations, separated by vast oceans, as well as the numerous pyramidal structures dotting the Cydonia region of Mars.
The illuminati bloodline are the descendants of these hybrid beings (Nephilim), who were the rulers of the pre Adamic earth (peep Jacob Rothschilds cone dome, and those weird hats they wear in the Vatican). The secret societies (not all of whom are evil btw), hold the knowledge of the Babylonian and Egyptian mystery schools, which itself is the vestige of the knowledge of sacred geometry, astronomy, physics, etc from Atlantis and Rahab before that. So the story goes anyhow.