The First World was destroyed by the Great Flood because the fallen angels were polluting the bloodline of man. Noah was found perfect and God told Noah His plans. Noah had 3 sons, Shem, Ham and Japheth. God put the animals, Noah, Shem, Ham and Japheth and their wives on the Ark and shut the door. The heavens were opened and the great deep was opened and God flooded the entire earth and killed all people and animals except for those on the Ark.
God told Noah to go into the earth and multiply. Noah's grandson Nimrod rebelled against God and built the Tower of Babel with his wife Semiramis and son Tammuz. They began the false religions about the fallen angels who were the men of renown of old before the flood.
Mythology is the Satyrs and Chemiras or your half man, half animal people, giants, one eyed giants, men with great strength. Your fallen angels rebelled with Satan and they went in to the daughters of men and had children by them which they called the giants or Nephilim.
These Nephilim ate all the food and then turned to eating the people. This mixed breed half human half fallen angel were genetically manipulated and even polluted the animal bloodline. Kind of reminds you of the "mouse with a man's ear growing on it." Manipulating genes is not a wise thing. Basically, the most ignorant and evil will do it.
Okay, back to the Tower of Babel, this is where God came down and confused the languages. Until this time all men spoke the same language. So the new language people went off in groups with those they could understand. This began the nations of this world.
I could bring you down to modern day but it would take too long.