Wikipedia
Pishachas (, ) are flesh-eating demons in Hindu mythology. Their origin is obscure, although some believe that they were created by Brahma. Another legend describes them as the sons of either Krodha (figuratively "Anger") or as Dakṣa’s daughter Piśāca. They have been described to have a dark complexion with bulging veins and protruding, red eyes. They are believed to have their own languages, known as Paiśāci.
According to one legend, they are sons of Kashyapa and Krodhavasa, one of the daughters of Prajapati Daksha.The Nilamat Puran of the 7th century mentions the valley of Kashmir being inhabited by two tribes: the Nagas and the Pisachas.
Piśācas like darkness and traditionally are depicted as haunting cremation grounds along with other monsters like bhutas and vetālas. Piśācas have the power to assume different forms at will, and may also become invisible. They feed on human energies. Sometimes, they possess human beings and alter their thoughts, and the victims are afflicted with a variety of maladies and abnormalities like insanity. Certain mantras are supposed to cure such afflicted persons, and drive away the Piśāca which may be possessing that particular human being. In order to keep the Piśāca away, they are given their share of offerings during certain religious functions and festivals.
The origin of Piśāca is unknown, although it may be the personification of the will-o'-the-wisp. Pāṇini, in his Aṣṭādhyāyi, described the Piśāca as a "warrior clan". In the Mahābhārata, the "Piśāca people" (equivalent to the modern day Nuristani people) are said to live in Northwest India and they are descendants of Prajāpati Kaśyapa.