Age of the Titans

The Titans were gargantuan, mountain-sized entities that roamed the world. Civilization was mostly nomadic and split into small tribes, who moved from place to place attempting to avoid contact with these monsters, since an encounter almost always ended in the tribe being decimated.
Very few written accounts from this age have survived, so only the most well practiced researcher would know any details. Most of what is known is based on oral tradition that was passed on through the centuries, until someone thought of writing it down.