"Lord Siva is called the Bhuta-natha, being assisted by various types of powerful ghosts and denizens of the inferno--Bhutas, Pretas, Pramathas, Guhyakas, Dakinis, Pisacas, Kusmandas, Vetalas, Vinayakas and Brahma-raksasas. (Of all kinds of ghosts, the Brahma-raksasas are very powerful. Brahmanas transferred to the role of ghosts become Brahma-raksasas.)"
Krsna Book, Chapter 63
"Ghosts and mischievous hobgoblins are also the creation of Brahma; they are not false. All of them are meant for putting the conditioned soul into various miseries. They are understood to be the creation of Brahma under the direction of the Supreme Lord."
"Lord Siva is described here as caracara-guru, the spiritual master of all animate and inanimate objects. He is sometimes known as Bhutanatha, which means "the worshipable deity of the dull-headed." Bhuta is also sometimes taken to indicate the ghosts. Lord Siva takes charge of reforming persons who are ghosts and demons, not to speak of others, who are godly; therefore he is the spiritual master of everyone, both the dull and demoniac and the highly learned Vaisnavas."
"Lord Siva is described here as bhuta-rat. The ghosts and those who are situated in the material mode of ignorance are called bhutas, so bhuta-rat refers to the leader of the creatures who are in the lowest standard of the material modes of nature. Another meaning of bhuta is anyone who has taken birth or anything which is produced, so in that sense Lord Siva may be accepted as the father of this material world."
"In Calcutta there are many butcher shops which keep a deity of the goddess Kali, and animal-eaters think it proper to purchase animal flesh from such shops in hope that they are eating the remnants of food offered to goddess Kali. They do not know that goddess Kali never accepts nonvegetarian food because she is the chaste wife of Lord Siva. Lord Siva is also a great Vaisnava and never eats nonvegetarian food, and the goddess Kali accepts the remnants of food left by Lord Siva. Therefore there is no possibility of her eating flesh or fish. Such offerings are accepted by the associates of goddess Kali known as bhutas, pisacas and Raksasas, and those who take the prasada of goddess Kali in the shape of flesh or fish are not actually taking the prasada left by goddess Kali, but the food left by the bhutas and pisacas."
"Prabhupada: That religiosity also different kinds: rajasic, tamasic, and sattvic, according to one's nature. The sattvic, they worship Visnu. The rajasic, they worship the demigods. And the tamasic, they worship bhuta, preta, pisaca..."
Srila Prabhupada Lecture, Bombay 04-08-74
"Pisaca worship is called "black arts" or "black magic." There are many men who practice this black art, and they think that it is spiritualism, but such activities are completely materialistic. "
"Sometimes due to sinful activities, too much attachment, a man becomes ghost. Ghost, there is ghosts. Bhuta preta pisaca. Not only this life, demonic life, but after death also, there are ghostly lives. They do not get this gross body. They remain in the subtle body, mind, intelligence, and ego. Due to their gross sinful life, they are punished by not getting a gross life. Because without getting a gross life, we cannot enjoy. With mind, I cannot enjoy rasagulla. I must have the tongue, I must have the hand, fingers, I can pick up, then... In the mind, I may think of eating or collecting rasagulla, but actually I do not get the taste."
Srila Prabhupada Lecture, London 07-29-73
"So one can remain like that, without this gross body and subtle body, material. Just like in the Vaikunthaloka, that is... But in the material world, when one is not covered by the gross body but subtle body, they are called ghosts or pramathas. Those who are good, not harmful, they are called pramathas. And those who are harmful... As in this material world there are good men and bad men, similarly, amongst the persons who has no this gross body, they are sometimes called ghosts and sometimes they are called pramatha."
Srila Prabhupada Lecture, Vrindaban 11-09-76
Bhaktivedanta Book Trust. Excerpted from various texts and purports of HDG A.C. Bhaktivedanta Swami Srila Prabhupada.