To get to the Spirit World you must go to the burial ground.
When you get to the burial ground you must find the tiki and put it in the shrine. That will open a door to Tomb taverns.find the building that has a beam going up into the ceiling. You have to get the mummies behind each door and bring them to that building. Listen to Flora she will guild you part of the time. When you have all the mummies in the room, Spirit world will open for you.

To do it you must press o,triangle,square tiwice. that way you get 100 feathers each time.