"There are two kinds of Asuras - one kind were divine in their origin but have fallen from their divinity by self-will and opposition to the intention of the Divine: they are spoken of in the Hindu scriptures as the former or earlier gods; these can be converted and their conversion is indeed necessary for the ultimate purposes of the universe. But the ordinary Asura is not of this character, is not an evolutionary but a typal being and represents a fixed principle of the creation which does not evolve or change and is not intended to do so.
These Asuras, as also the other hostile beings, Rakshasas, Pishachas and others resemble the devils of the Christian tradition and oppose the divine intention and the evolutionary purpose in the human being: they don't change the purpose in them for which they exist which is evil but have to be destroyed like the evil.
The Asura has no soul, no psychic being which has to evolve to a higher state; he has only an ego and usually a very powerful ego; he has a mind, sometimes even a highly intellectualised mind; but the basis of his thinking and feeling is vital and not mental, at the service of his desire and not of truth.
He is a formation assumed by the life-principle for a particular kind of work and not a divine formation or a soul."
Sri Aurobindo Letters on Yoga vol.1 pg. 394