The Asuras were the psychics of the ancient times. They cultivated their mind-force in order to use it for personal aggrandizement. They were Yogis, but their Yoga was divorced from pure spirituality, because their object was not spiritual. All they wanted was power by which to overpower others and keep them under subjection for their own earthly benefit. Some of them were exceptions to the rule; they cultivated their Sāttwic powers to some extent along with the development of Rājasic powers. These became great heroes in battles and some of them made very good kings. Others developed merely Rājasic and Tāmasic powers of the mind and became tyrants and oppressors of all good people. Wherever and whenever the earth groaned under the burden of their sins, partial incarnations of Vishnoo came down to earth to destroy them and bring peace and goodwill among mankind once more. But those Asuras who had only their Tāmasic (dark) mind-force developed, were the lowest of them all. Their minds were all dark and their deeds were all black. Their natural inclination was to do mischief to people for the sake of the mischief itself. These were called demons. These demons can be found reborn among us all, in the most advanced centres of civilization, but they are now shorn of their former psychic force. The mind's natural inclination, however, is still in them. They take to external means to satisfy this inclination of killing or hurting or doing mischief for the sake of the act itself. Formerly their dark mental powers were their most potent weapons. Through those psychic powers they could transform themselves into any shape they concentrated upon, and if they failed to assume the form of a saint or a god, it was because they could not grasp the idea of the personality of such pure souls with their impure minds. To assume the form of a beast was the easiest thing for them, because they were nothing but human beasts in their nature. They could also assume elemental forms too, such as a whirlwind, etc., as in Krishna Leelā. The modern Asuras cannot do any such thing because their mind-forces are scattered and distracted. The chief cause why people generally cannot be a high yogi or a black-psychic demon is the density of Rāja and Tama that at present pervades Nature, of which all beings are parts and products, which disturbs concentration.