Therion (, beast) is a deity found in the mystical system of Thelema, which was established in 1904 with Aleister Crowley's writing of The Book of the Law. Therion's female counterpart is Babalon, another Thelemic deity. Therion, as a Thelemic personage, evolved from that of "The Beast" from the Book of Revelation, whom Crowley identified himself with since childhood, because his mother called him that name. Indeed, throughout his life he occasionally referred to himself as “Master Therion” or sometimes “The Beast 666”. He wrote:

Before I touched my teens, I was already aware that I was THE BEAST whose number is 666. I did not understand in the least what that implied; it was a passionately ecstatic sense of identity.