THE NEPHILIM.

The Nephilim were offspring of the "sons of God" and the "daughters of men" before the Deluge according to Genesis 6; they were said to later inhabit Canaan at the time of the Israelite conquest of Canaan according to Numbers 13. A similar biblical word with different vowel-sounds is used in Ezekiel 32 to refer to dead Philistine warriors.
The Nephilim are to be perceived as "those that cause others to fall down." The Dead Sea Scroll (Qumran) contains the earliest known reference to the phrase "children of Seth," stating that God had condemned them for their rebellion and other early references tell about how they mingled with the daughters of Cain.
In the Epistle of Jude, a parallel is draw to Genesis 6 and it refers to the paternity of Nephilim as heavenly beings who came to earth and had sexual relationship with women, creating a superhuman race.
The story of the Nephilim is further elaborated in the apocryphal Book of Enoch. It connect the origin of the Nephilim with fallen angels. It refers to both good and bad Watchers. The Watchers were angels dispatched to Earth to watch over the humans. They were surrounded by the demon spirit of lust and his legions, that attacked them and obtained victory over their spiritual bodies making them fall with lust for human women, and at the prodding of their leader, Satan, that illicitly controlled the human race, the offspring of the Fallen Watchers mating with the daughters of men, the Nephilim developed as savage race of giants who pillaged the earth and endanger humanity. Eventually God allows a Great Flood to rid the earth of the Nephilim, but first sending His Archangel to warn Noah so as not to eradicate the human race. The Watchers were bound "in the valleys of the earth" until Judgment Day.
The first Book of Enoch devotes much of its attention to the fall of the Watchers. The Second Book of Enoch addresses the Watchers who are in the Fifth Heaven where the Fall took place. The Third Book gives attention to the Unfallen Watchers. The Book is based in the interpretation of the Sons of God passage in Genesis 6, according to which angels descended their condition and married with human females, giving rise to a race of hybrids known as the Nephilim. The term "Irin" is primarily applied to disobedient Watchers who numbered a total of 200, and of whom their leaders are named, but equally Aramaic "Iri"("watcher" singular) is also applied to the Obedient Archangels who chain them, such as Raphael.
Watchers also are mentioned in both plural and singular forms in the Book of Daniel,  chapter 4, making reference to their holiness. The term is introduced by Nebuchadnezzar who says he saw "a watcher, a holy one come down from heaven." He describes how in his dream the watcher says that Nebuchadnezzar will eat grass and be mad and that this punishment is "by decree of the Watchers, the demand by the Word of the Holy Ones" ... "the living may know that the Most High rules in the kingdom of men." After hearing the king's dream Daniel considers for an hour and then responds:"And because the king saw a Watcher, a Holy One, coming down from heaven and saying, 'Cop down the Tree and destroy it, but leave the stump of its roots in the earth, bound with a band of iron and bronze, in the tender grass of the field, and let Him be wet with the dew of heaven, and let His portion be with the beasts of the field, till seven periods of time pass over Him,' this is the interpretation. O, king: It is a decree of the Most High, which has come upon my lord the king, that you shall be driven from among men, and your dwelling shall be with the beasts of the field. You shall be made to eat grass like an Ox, and you shall be wet with the dew of heaven, and seven periods of time shall pass over you, till you know that the Most High rules the kingdom of men and gives it to whom he will.' "