A tovil is commissioned by a household for a named patient, someone whose illness, misfortune or wasting fear has been diagnosed, usually through an astrologer or the adura himself, as the work of the yakku, the demons who fasten on people in moments of aloneness and fright. The ceremony runs from evening to past dawn in a temporary arena built at the house, with palm-leaf structures for the demons, and it proceeds as a carefully graded drama. The evening watches summon the afflicting beings with drumming and chanted invitations, and offerings are set for them; the midnight watches bring the demons bodily into the arena, danced by masked performers whose whirling, torch-lit entrances are among the most powerful theatrical images in South Asia; and the closing watches, toward morning, do the essential work, turning terror into comedy. The demons, so overwhelming at midnight, are made to appear before the patient in daylight as buffoons, questioned in knockabout dialogues, tricked, mocked and dismissed, their claim on the patient dissolved in the household's laughter.
The Sanni Yakuma sequences present the eighteen sanni, each mask a diagnosis, blindness, fever, delirium, paralysis, until the demon of each disease has bowed to the authority of the Buddha invoked over the whole rite. The patient, seated through the night at the centre, ends the ceremony re-placed in an ordered, Buddhist, daylight world, which is, on the anthropological reading, exactly the cure.