How are the Overlords characterized in this first section of the novel (they are never physically described)? Are there any words/ideas in these characterizations that seem to be repeating?

The Overlords are the mysterious beings that invade Earth. They keep their identity a secret for the first fifty-five years of occupation. The Overlords' appearance is that of the Devil. They are covered in a hard, black shell, and have horns, small leathery wings and a barbed tail. Large in stature, they exude an acidic smell. The Overlords are also sensitive to sunlight, wearing sunglasses whenever outdoors.