@SnoozyLucy7 I believe the 'heroes of old, men of renown' described in the Bible refer to the stories of demigods and goddesses (children of gods and mortals), giants and great warriors in ancient Greek mythology and the like, which was inspired by the Nephilim.
The Bible also says they existed afterwards (after the flood) and it's my understanding that Ham, one of Noah's sons, settled in the land of Caanan. Ham was cursed for disrespecting his father. The sons of God (fallen angels) once again had children with women in this area. The ancient Sumerians, Akkadians, Assyrians and Babylonians have myths relating to the Annunaki/Anakim (meaning 'princely offspring' or 'from heaven who came to earth').
When the Israelites scouted out the area where the Caananites were living they returned saying "We saw the Nephilim there (the descendants of Anak come from the Nephilim). We seemed like grasshoppers in our own eyes, and we looked the same to them". Anak means tall (ie giant) and relates to the Annunaki or Anakim.
God forbids sexual relations with the Caananites and some nearby tribes and tells the Israelites to destroy the cities, leaving none alive. Again, as before the flood, the bloodline of the human race was contaminated and needed purification. In doing this, Satan (aka Lucifer - chief fallen angel) was trying to prevent his own downfall with the arrival of the Messiah (Jesus), who was to come from the tribe of Judah.