The netherworld
The other world is the world of dead people and spirits in mythology. The myths about the other world developed the views of people on the other world connected with the reaction of the society to the death of one of its members and the sepulchral rites. The death was taken as the break of the normal way of life and activity of the society in the result of impact of paranormal powers such as witchcraft and evil forces curses, etc. The psychological fear of death in connection with the biological danger of decomposed body was personified in the dead person. That is why the sepulchral rites had the purpose to isolate the dead and the harmful impact of the death with the dead person.
But there was another trend that existed simultaneously with the previous one. People wanted to keep the dead person with themselves as closed as they could so that the society wouldn't suffer without the dead one and his activity. So, this was the base for the ancient ceremonies of burial in certain inhabited areas, in special houses, in special buildings for dead people, in owns of dead.
And in such way the person was dead and alive at the same time. And people reflected their views on the world on base of their ideas on the other world. In such way the other world was very dual. But this duality was the reflection of the duality that the world has. Black and white, female and male, good and bad and in the result life and death is duality that is in the whole world.