Once upon a time, there lived two gods - Papatuanuku earth mother, and Ranginui sky father. They had many children, who grew to be gods as well. For instance, Tangaroa god of water, sea and lakes, Ruamoko god of Earthquakes and Volcanoes etc.
However, Papatuanuku and Ranginnui also gave birth to all mortal beings as well as all immortal beings. This means they gave birth to humans as well.
However, Papatuanuku was especially fond of one of her children. The humans themselves. She was so fond of them that she gave them a present. This present was only accessible by the humans themselves. This present was a staircase - a terrace - that led them to the land of the gods, from the land of the mortal.
To begin with, the humans respected this privilige, presenting themselves to the gods as the mortals as they were.