Tales of Apep's battles against Ra were elaborated during the New Kingdom. Storytellers said that every day Apep must lie below the horizon and not persist in the mortal kingdom. This appropriately made him a part of the underworld. In some stories, Apep waited for Ra in a western mountain called "Bakhu", where the sun set, and in others, Apep lurked just before dawn, in the "Tenth region of the Night". The wide range of Apep's possible locations gained him the title "World-Encircler". It was thought that his terrifying roar would cause the underworld to rumble. Myths sometimes say that Apep was trapped there, because he had been the previous chief god overthrown by Ra, or because he was evil and had been imprisoned.