The Nephalim are considered ‘the fallen ones’. Others call them Giants.
They are also regarded as the offspring of fallen angels and human women, from Genesis chapter 6. Emphasis mine.
1And it came to pass, when men began to multiply on the face of the earth, and daughters were born unto them,
2That the sons of God saw the daughters of men that they were fair; and they took them wives of all which they chose. And the Lord said, My spirit shall not always strive with man, for that he also is flesh: yet his days shall be an hundred and twenty years.
4There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old, men of renown.
What I really find fascinating is all cultures have stories regarding gods coming down to Earth and inhabiting with humankind. There can be an argument these same gods are the fallen angels. Most in the western world know of the Titans and other Greek mythology creatures.
The website thoughtco.com has a good listing of these gods and goddesses.
There was a recent show on The History Channel, where two brothers went across United States. The show called, Searching for Giants, aired in 2014, and provided some interesting finds in the archives across the States.
You may be able to find some snippets of the videos in YouTube or other sites.
In my novel, Sight and Sound, I created Forward, providing some background on the world I am creating. It was taken from the cultural mythology and Book of Enoch.
The Book of Enoch chapter 15: 8-11 Emphasis mine.
And now the giants, who have been begotten from body and flesh, will be called evil spirits on earth, and their dwelling-places will be upon the earth.
9. Evil spirits proceed from their bodies; because they are created from above, their beginning and first basis being from the holy watchers, they will be evil spirits upon the earth, and will be called evil spirits.
10. But the spirits of heaven have their dwelling-places in heaven, and the spirits of the earth, who were born on the earth, have their dwelling-places on earth.
11. And the spirits of the giants, who cast themselves upon the clouds, will be destroyed and fall, and will battle and cause destruction on the earth, and do evil; they will take no kind of food, nor will they become thirsty, and they will be invisible.
Links to my available Sight and Sound novel, can be found here.