"The demons who were born from the body of Brahma were called Yaksas and Raksasas because some of them cried that Brahma should be eaten and the others cried that he should not be protected. The ones who said that he should be eaten were called Yaksas, and the ones who said that he should not be protected became Raksasas, man-eaters. The two, Yaksas and Raksasas, are the original creation by Brahma and are represented even until today in the uncivilized men who are scattered all over the universe. They are born of the mode of ignorance, and therefore, because of their behavior, they are called Raksasas, or man-eaters."
"Similarly, one can go to many ghostly planets and become a Yaksa, Raksa or Pisaca. 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."
"There are some types of living entities in the form of human beings whose living conditions and eatables are most abominable. Generally they eat flesh and fermented blood, which is mentioned in this verse as ksatajasavam. The leaders of such degraded men known as Yaksas, Raksasas, bhutas and pisacas, are all in the mode of ignorance. They have been placed under the control of Rudra. Rudra is the incarnation of Lord Siva and is in charge of the mode of ignorance in material nature. Another name of Lord Siva is Bhutanatha, meaning "master of ghosts." Rudra was born from between Brahma's eyes when Brahma was very angry at the four Kumaras."
"The demon Yaksas are by nature very heinous, and by their demoniac power of illusion they can create many strange phenomena to frighten one who is less intelligent."
"Out of disgust, Brahma threw off the body of ignorance, and taking this opportunity, Yaksas and Raksasas sprang for possession of the body, which continued to exist in the form of night. Night is the source of hunger and thirst."
"O club in the hand of the Supreme Personality of Godhead, you produce sparks of fire as powerful as thunderbolts, and you are extremely dear to the Lord. I am also His servant. Therefore kindly help me pound to pieces the evil living beings known as Kusmandas, Vainayakas, Yaksas, Raksasas, Bhutas and Grahas. Please pulverize them."
"Raksasas are understood to be accustomed to eating their own sons, as snakes and many other animals sometimes do. At the present moment in Kali-yuga, Raksasa fathers and mothers are killing their own children in the womb, and some are even eating the fetus with great relish. Thus the so-called civilization is gradually advancing by producing Raksasas."
"Raksasis learn mystic powers by which they can travel in outer space without machines. In some parts of India there are still such mystical witches, who can sit on a stick and use it to fly from one place to another in a very short time. This art was known to Putana. Assuming the feature of a very beautiful woman, she entered Nanda Maharaja's abode, Gokula."
Bhaktivedanta Book Trust. Excerpted from various texts and purports of HDG A.C. Bhaktivedanta Swami Srila Prabhupada.