What were the Nephilim, and what role did they play in the Bible beyond just being mentioned? Did the Nephilim that are mentioned in Genesis 6:4 do anything beyond just existing?
The Nephilim are a subject of much debate. There are a number of views on what they were, the two prominent views being the Sethite view and the Angelic view. Both are an opinion on who or what the "sons of God" are.

The Nephelim are most notably mentioned in Genesis and seem to be a driving decision to send the Flood of Noah.


  The Nephilim were on the earth in those days—and also afterward—when the sons of God went to the daughters of humans and had children by them. They were the heroes of old, men of renown. Genesis 6:4


A few things stand out in this one verse:


The "sons of God" procreated with "daughters of humans" which created the Nephilim.
They are "heroes of old, men of renown." They did fantastic things.
They were on the Earth "afterward" presumably the Flood.
This short narrative on them is right in the midst of the introduction to Noah and the Flood, hinting that they may have been a reason God brought on the Flood.


Generally, the Sethite view holds that the Sons of God were the righteous men descended from Seth; they praised and worshiped God. The daughters of men are women descended from Cain, who came from wickedness. This view contends that there is nothing particularly special about these persons and it is meant to highlight that the mixing of the righteous people of Seth with the wicked people of Cain led to further wickedness and their subsequent total destruction by the Flood.

Generally, the Angelic view holds that the Sons of God were angels or some other spiritual creatures that procreated with human women. This view contends that this act alone was wicked and an indication that these angelic beings were fallen from God's grace, therefore the offspring were inherently wicked. This view also contends that the offspring were giants and beyond human capabilities.

With both of these views, there is very little Biblical support. However, I find the suppositions and theories very interesting and even fun to research in a science fiction kind of way.

The extent to which your exact question is answered depends on which view you want to hear. From the Sethite view it pretty much stops at Goliath, if you call him a Nephilim because he was a giant. From the Angelic view, we can go all the way through Revelation. Outside of the Bible we can make many suppositions and links to mythology, but that is a bit outside of the scope of this site.

Here are some of the major points concerning the Nephilim:

Points from the scripture


A people in Canaan are later called Nephilim and giants in Numbers.
A man named Anak is listed as a forefather of them. His father is listed as Arba.
It seems that in ancient times, they also went by Anakin, Anakim, or Anakites, all clearly derivatives of the name Anak. They also went by Rephaites; that name's origin is a little less clear.
Three sons of Anak are mentioned by name as if they are still living.
Goliath was a giant; so were his four brothers. This implies that they may have been part of a nearly extinct family of giants, possibly Nephilim descendants.
Some of the Apocrypha go into detail about the Nephilim, the Book of Enoch is most notable.


Points from the Sethite View


Typically, those holding the Sethite view are not biblical literalists and do not believe in the infallibility of the Scripture. Therefore, their explanations are quite naturalist.
Heroes of old is difficult to explain, but it is usually thus: being persons from both lines, the Nephilim united the two lines, setting themselves up as kings and such, and led Earth into prosperity, although at the cost of righteousness.
They were 'on the Earth afterward' is a scribal insert from the original text. The few times they are mentioned in Numbers is by exaggerating scouts; they even went so far as to call them giants. Though they may have been, the source is shaky.


Points from the Angelic View


Typically, those holding the Angelic view are biblical literalists and believe in the infallibility of the Scripture. Therefore, their explanations do not hesitate anything so long as the text of the Scripture mentions it.
They were heroes because they were giants. That much we can know for sure. There are obvious advantages to being larger than everyone else. Goliath is often pointed to as evidence that the Nephilim must have been giants, too. Being half angel or something else non-human they might have had impressive abilities. They may have been able to do things that we cannot even comprehend. I have heard everything from the ability to levitate to supernatural strength to unsurpassed cunning. This easily puts them in line to seize and rule the entire Earth and become "heroes".
There have been many draws from mythology and pagan gods to the Nephilim, with some even arguing that characters like Hercules and Ra were real at least in part and were Nephilim.
A reason the Flood was decided was to wipe out the Nephilim, which were an abomination to God. The fact that some survived was reason for the flat out genocide of some of the peoples of Canaan; the Nephilim needed to be destroyed.
Some have purported that demons are the disembodied Nephilim that have perished. Demons seem obsessed with possessing persons because they are disembodied. Their soul is not like a human soul. They would surely not be allowed in heaven and perhaps there angelic abilities keep them from spiritual imprisonment elsewhere. The story of the group of demons called "Legion" in Mark 5 illustrate this.
I read a fascinating, and frankly creepy, book that connected the Nephilim with alien abductions and went on further to name them as the 2nd beast of Revelation that makes the world bow down and worship the image of the 1st beast. It is completely outlandish, but water tight once a few assumptions are taken.


Wikipedia has a fantastic article on the Nephilim, however, it seems very disorganized to me.



*I wrote an essay on the topic, but I could not find it. I did find my preliminary notes. Here they are.

The following are all the verses that are or might be related to the Nephilim.

Gen. 6:4—The Nephilim were on the earth in those days—and also afterward—when the sons of God went to the daughters of men and had children by them. They were the heroes of old, men of renown.
Gen. 14:5—[They] went out and defeated…the Emites[see Dt. 2:10].
Gen. 23:2—Kiriath Arba is a name for Hebron which is in Canaan.
Gen. 35:27—Kiriath Arba is Hebron
Nu. 13:28—They went up through the Negev and came to Hebron, where Ahiman, Sheshai and Talmai, the descendents of Anak, lived.
Nu. 13:33—We saw the Nephilim there (the descendents of Anak come from the Nephilim).
Dt. 1:28—We even saw the Anakites there.
Dt. 2:10—(about the land of Ar) the Emites used to live there—a people strong            and numerous, and as tall as the Anakites. Like the Anakites, they too were considered Rephaites, but the Moabites called them Emites.
Dt. 9:2—(on lands across the Jordan) The people are strong and tall—Anakites!
Jos. 11:21,22—Joshua destroyed the Anakites. No Anakites were left in Israelite territory; only in Gaza, Gath, and Ashdod, did any survive.
Jos. 14:12—(Caleb talking) You yourself heard then that the Anakites were there and            that their cities were large and fortified.
Jos. 14:15—Hebron used to be called Kiriath Arba after Arba who was the                  greatest man among the Anakites (Hebron is also mentioned other times in the Bible, but long after the Anakites were all ran out).
Jos. 15:13,14—Arba was the forefather of Anak. Caleb drove out the 3 Anakites: Ahiman, Sheshai and Talmai from Hebron.
Jos. 21:11—Kiriath Arba is Hebron; Arba was the forefather of Anak.
Jdg. 1:10—They advanced against the Canaanites living in Hebron (formerly            called Kiriath Arba) and defeated Ahiman, Sheshai and Talmai.
Ne. 11:25—People of Judah lived in Kiriath Arba.
1 Sam. 17—The story of Goliath begins here. Goliath is clearly described as a giant. He is from Gath. This was during war with the Philistines.
1 Chr. 20:4-8 &amp; 2 Sam. 21:15-22—In these verses we learn Goliath had a giant brother named Lahmi and was descended from Repha, though he was called a Gittite. There is also a short description of a 6-fingered, 6-toed giant Rephaite named Sippai or Saph. David is almost slain by a Rephaite named Ishbi-Benob.
1 Chr. 20:8—Seems to be the nail in the coffin for the Rephaites at Gath. Says they fell at David's hands.

The following were preliminary conclusions. They are from a biblical literalist view.

The Nephilim were a real people who lived before and after the flood. That is very clear in the Scripture. They received the name Anakites from Anak who was a descendant to Arba
who was "the greatest man among them." The land they lived in was called Kiriath
Arba, but it was later called Hebron. The mention of the Emites leads me to conclude that these people were also from the Nephilim, but perhaps their lineage was lost or unknown. Dt. 2:10 shows the confusion of who they were, but it strongly asserts that they were also large and strong people. "Rephaites" is only mentioned in passing in a few areas. It is possible, that because of confusion and different people using different names, that Anakites, Emites, and Rephaites were all the same people; it is also possible that Gittites were the same people as well. Dt. 9:2 hints that there were other tribes of people who may have been related to the Nephilim through the Anakites, or they may be directly related to the Nephilim. Perhaps like Israel, they were divided into tribes, maybe from the sons of Arba or Anak. The mention of Ahiman, Sheshai and Talmai in Nu. 13:28 and Jos. 15:13,14 hints at this possibility; it is not a stretch to assume that these three persons were chiefs, kings, or some other kind of leaders fr their people. When we look at Goliath the scriptures clearly call him and his family Rephaites, who are descendants of Anakites. There are quite a few details about them, and they are all surrounded by stories of war with the Philistines. The Philistines clearly were allied with them or perhaps the Rephaites were Philistines. Considering the Philistines were eventually completely destroyed, the last of the descendants of the Nephilim were either killed or integrated into other, normal races. If there were (or are) surviving Nephilim the Bible does not explicitly record it.