These can include physical illnesses such as stomach disorders or paralysis, or mental problems. Often they are a mixture of both. A yakadura (demon doctor) will diagnose the sickness and arrange treatment. If a simple ritual is not sufficient to cure the patient he will arrange for a major exorcism ceremony of the appropriate type.
These ceremonies begin at sunset and finish at dawn, and consist of a set series of seperate rituals involving prayers and invocations to gods and demons, trances and possession, chanting, dancing and drumming. Ancient legends are retold and reenacted,
And there will be laughter.
After these evil demons have been summoned with all the proper respect and appropriate offerings, they will finally be made fun of and ridiculed!
Laughter is a major part of the low country ritual because who can fear what you see as ridiculous and absurd?
Ironically, while the masks used in these rituals are sold all over the country, the ceremonies themselves are becoming rarerer and are almost unknown outside Sri Lanka except to academics.
I am no expert, but as there is little information on the internet I thought I should try to fill the gap. This site contains photos and sound samples from some of the exorcisms I've been lucky enough to see.
Apologies for any inaccuracies. Please feel free to email me with any corrections or further information.