Self described as 'The Beast 666' and a practiser of sorcery and ritual bestiality he would become known to his contemporaries as 'The Wickedest Man in the World'.
Crowley was born the son of a preacher, and raised in a religiously devout home. He seemed, in his childhood, bound for the same path.
Upon the death of his father, whom he worshipped, Crowley felt utterly betrayed by religion and God, and decided to embark on a path that would lead him to eventual ruin in every way conceivable.
Crowley was not an atheist, nor a nihilist - he believed in 'Magik'. He joined an exclusive society known as the Golden Dawn, and practised his 'art' to such an extent he was elevated to the highest ranks, until he decided it was not enough.
Crowley wanted to pursue the darkest of arts, 'free' of the flimsy moral constraints such organizations seemed to adhere to. In order to do this he broke with the 'Dawn', and eventually formed his own cult of acolytes and followers called the Temple of Thelema.
His story is as infamous as it is otherworldly.
I will be writing a piece on his ideas soon, and in my research I found this excellent documentary which is freely available on YOUTUBE (at least in my region).