So the Nephilim are nothing new, but they remain elusive still.
I wrote about them more than once (twice I believe) but I have new information based on a new book that I've read (I don't have the author's permission to talk about it, so I don't know if I can post the title here).
So to start off, the Nephilim were the children of The Watchers, though it seems to be confusing. The word Nephilim means 'to fall' (with -im meaning plural). The 'Nephilim' didn't fall from Heaven, they were never there to begin with. They were the children of the Watchers, but still, titles don't matter. They were here and they were important.
So I'll start by saying that I don't like how people represent the Nephilim. They are not horned devils or abominations or anything terrible looking. It mentions in many old texts that we are made in their image. So why would the 'gods' make the angels demonic? They look like us too, or at least take our form when showing themselves to humans. So why would two races that look the same spawn evil devil rage beasts?
Nephilim are said and shown to be pretty powerful. They are both good and bad like everyone else, but there are some who have helped us in the past (Prometheus giving fire to the mortals is one that comes to mind).
It also says that the Nephilim were beautiful creatures, they appeared both as men and women as well. So I can not figure out where this image of ugly creatures came from.
Another thing about the Watchers, it was said that their wings were 'clipped' or you could say 'taken away'.
So these old reports of the gods flying around in 'chariots' makes sense if they needed to get around. If they could fly before, they would want to do the same later. As they were vastly intelligent, they would know how to make something to assist them in their flying. Though it could be different as I have never seen one before.