The sumerians called them Nephilim. They are referred to as "giants" in the Old Testament. This is the reason why the royalty interbreed. According to the stories, their leader, Chronos, is imprisoned in the place that the ancient greeks called "Tartarus" which is the main island volcano of the Canary Islands. He is said to be released in the last days, I don't know when that is exactly but possibly next year.

They think they have a chance I suppose, because Chronus is capable of much the same stuff as Atlas and I guess he has an entourage of "angels" who are lesser but similarly powerful. But they have been stuck here and Atlas and co have had all the time in the world to learn more things.