The Nephilim are first mentioned in Genesis 6:1-4 were the Bible says the following:
When man began to multiply on the face of the land and daughters were born to them, 2 the sons of God saw that the daughters of man were attractive. And they took as their wives any they chose. 3 Then the Lord said, “My Spirit shall not abide in man forever, for he is flesh: his days shall be 120 years.” 4 The Nephilim were on the earth in those days, and also afterward, when the sons of God came in to the daughters of man and they bore children to them. These were the mighty men who were of old, the men of renown.
So who or what were the Nephilim? Well the most popular view of what the Nephilim were with the interpretation of Genesis 6:1-4 is that the Nephilim were the offspring of sexual relationships between the “sons of God” or fallen angels and the human women.
Therefore when fallen angels or demons mated with human females, what resulted through such a sexual union was the offspring or hybrids called the Nephilim.
So what did the Nephilim look like? The Nephilim have been described as being a race of giants and hybrids. Therefore they had a mixture of human and demonic DNA.
According to sources such as the Book of Enoch and the Bible, the Nephilim had great size, great influence, great power and they were extremely wicked and evil.
They were also treated as “gods” because of their stature and power.
Genesis 6:1-7 when read in context gives us the picture that one of the main reasons why God may have decided to destroy the earth through the great flood was because of the existence of the Nephilim.
It’s believed that one of the reasons why the demons mated with humans to produce the Nephilim was so that they could pollute the human bloodline and prevent the future coming of the Messiah who is Jesus Christ.
Therefore the more the population of the Nephilim increased and mated with humans – the more polluted the human DNA and bloodline would become.
Furthermore the existence of the Nephilim accelerated the wickedness in the earth to the point that God decides to destroy the earth by a great flood. Genesis 6:5 says that God saw that the wickedness of man was great in the earth and such that every intention of the thoughts of his heart was continuously evil.
Therefore the influence of the Nephilim both physically and spiritually polluted and affected mankind to the point that it reached irredeemable proportions. God’s solution was to flood the earth
In context, Genesis 6:4-7 says The Nephilim were on the earth in those days, and also afterward, when the sons of God came in to the daughters of man and they bore children to them. These were the mighty men who were of old, the men of renown. 5 The Lord saw that the wickedness of man was great in the earth, and that every intention of the thoughts of his heart was only evil continually. 6 And the Lord was sorry that he had made man on the earth, and it grieved him to his heart. 7 So the Lord said, “I will blot out man whom I have created from the face of the land, man and animals and creeping things and birds of the heavens, for I am sorry that I have made them.”
In conclusion, the flood was not only the result of wickedness of mankind but it was also the result of the existence and great influence of the Nephilim.