Leyaks are humans who are practicing black magic and have cannibalistic behavior. Their mistress is the "queen of Leyak", a widow-witch named Rangda, who plays a prominent role in public rituals. Her mask is kept in the village death temple and during her temple festivals, she is paraded. Besides leyaks, demons are said to be the followers of Rangda.
Leyak are said to haunt graveyards, feed on corpses, have power to change themselves into animals, such as pigs, and fly. In normal Leyak form, they are said to have an unusually long tongue and large fangs. In daylight they appear as an ordinary human, but at night their head and entrails break loose from their body and fly. Leyak statues (a head with a very long tongue and sharp fangs) are sometimes hung on a wall for house decoration.
In practice, Balinese people sometimes attribute certain illness or deaths to leyaks. A balian (Balinese traditional healer) will conduct a seance to identify with witchcraft who is responsible for the death. During the seance, the spirit of the dead will directly or indirectly point to his/her attacker. However, vengeance by the victim's relatives or family is usually counseled against, and people are advised to leave any action to the spirits themselves. Hence, the suspicions and fears of the family and relatives are confirmed, but revenge upon the witch is discouraged by the healers.
In Sri Lanka, 1000s of miles away from Bali, legendary demons and healing rituals show some astonishing similarities. The term 'Yak' is used to identify the powerful people or demons lived in the past in that Island. The legends say those Yak or 'Yakshas' spread their power all over Asian region. 'Le' in Sinhala means Blood. 'Le-Yak' in present day Sinhalese language means Blood Demon or blood sucking demon.