Ongons are amongst the most important shamanist tools in Mongolia and they come in many different forms. They are essentially ritual spirit houses or empowered shrines, to give a home to spirits. Common materials used to make ongons include wood, leather, felt, rocks, paper, fur, feathers, straw, and metal. Some ongons are highly abstract in form while others are much more realistic. Ordinary people may make an ongon, but it is empowered by a shaman who calls the spirit to occupy it. Ancestor spirits or animal spirits occupy most ongons. However, some contain very powerful nature spirits or house the souls of powerful shamans. Since most ongon spirits have lived as humans or animals in the past, they are believed to have human-like emotions and memories, and so they are treated with respect. After being empowered by a shaman, an ongon is honoured by being placed in the sacred area of a ger (the traditional round felt tent of the nomads - often known as a yurtin the West), and fed offerings of liquor, blood, milk, or fat. When a spirit is no longer useful or desired, the ongon is either burned respectfully or placed out in nature so the spirit can return to the natural world from which it had been called.