Legends tell of strange things that might have happened to the Thirteenth Tribe and Earth. They tell of the tribe having known great rises and falls in their civilisation.
Ancient myths explain this due to strange creatures that either inhabit the planet, or were brought there for some reason. Beasts of huge proportions - up to 150 metrons high and weighing several hundred thousand tons - with terrifying abilities - including death rays, mental powers, flight, teleportation and more - who exist to hinder or save humanity.
This attempts to reconstruct some of these monsters into terms that Colonial (or Cylon) commanders can understand in case these beasts ever find the other branches of humanity, or humanity finds Earth.