Indonesia is predomintantly Muslim but underlying that fact are a strong set of locally held beliefs, pre-dating Islam. The Balinese have made some of therse beliefs a part of their Hindu religion. The Muslims, however, have to run a double line, professing belief in Islam, while quielty going about their other proactices. An article in a guide book written by Bill Dalton talks about this.
‘Indondonesians are preoccupied with mystical and devotional matters, their spritualism eclipsing the basic rationalism of Islam. Even the President believes in a Javanese brand of mysticism and omens. Mysticism is alive and well in east and central Java, where the sultan of Yogya is still looked upon as a god. Ritul meals (selamatan) are attended by neighbors and friends to appease the spirits during important transitional events. Army generals helicopter into the camps of mystics in E.Java (Blitar) for spiritual consultations. Witch doctors (dukun) exorcise evil spirits from granaries, temples, cars, hotels, swimming pools. Thieves use black magic to rob houses.
There are devils, ghosts which steal children (wewe) and lure young men (puntianak). On Ambon, white-magic priests (mawang) work harmoniously alongside the Christian and Muslim religious leaders of a village. The staunchly Islamic Makassarese of S. Sulawesi worship large stones, flags, swords, umbrellas, and plows, presenting regular offerings of food and betelnut, and even on more important occassions, animals are even sacrificed to them. Catholics of Yogya use gamelan music to celebrate mass, and some Christians of Torajaland (Sulawesi), sacrifice bulls to the memory of the dead raja. It’s far easier to learn when religions began in Indonesia, than it is to know when they ended.’
Any time there is a disaster happening, or about to happen (volcano about to erupt etc.) villagers will instantly perform local ceremonies to the gods of the mountain, and lay offerings. I think its cool and provides a mental link between the people and their local environment.