The first-born nephilim; those who were born directly of angelic 'fathers' and human mothers on Atlantis. As has been previously mentioned, the only 'stable' children to be engendered by the Fallen occurred within twenty years of their arrival once, it is theorised, their DNA settled down and stabilised within their new bodies and became less volatile. In other words, once these children at least looked mostly human.
We have given you the general classifications for most of the nephilim but, with those Atlan born specimens that survived the Flood, such tidy ordering is a less simple endeavour.
Recall that, following the Flood, the ocean-born survivors went where the storms carried them. Some ended up in what were to become North or South America; others from the West coast of Ireland all the way across Europe to Asia. Some even made it as far as what would become Australia and New Zealand. In these locations, they successfully posed as gods and displayed abilities to back up their claims as well as demand loyalty and sacrifice. Not all of these feats were technologically achieved, many were native talents. Think of a so-called god of the ancient world, think of what it was claimed they could do. Think of a being who can really do that.
Now you will be pleased to know that a great many of the First died in the completely lost to history Nephilim War of 700 AD. A great many of the Heroes and Demi-Gods died with them of course but the good news is that there are very few of the First left. Of course, I do not need to tell you about one of Darwin's favourite sayings now do I?