Who was Mr. Crowley?

Mr. Crowley is all that is evil...he worshipped the dead, he was a satanist and many evil movie characters had the the last name crowley, but who is mr crowley really? a reincarnation of the devil himself? he is actually an English occultist name aleister. He was known to be the wickedest man on earth. He greatly influenced Ledzeppelin and The Beatles.