Complex sentence: The story goes on that God was so angry with them he threw them out of Heaven and cast them to Earth as mortal demons, the Nephilim, where they created such a disturbance on Earth that God sent the flood to cleanse the planet.
Split into simpler sentences: The story goes on that God was so angry with them he threw them out of Heaven and cast them to Earth as mortal demons. Nephalim created such a disturbance on Earth that God sent the flood to cleanse the planet.