Aleister Crowley was an English occultist, ceremonial magician, poet, novelist, mountaineer, and painter. As the founder of the religion of Thelema in the early 20th century, he identified as its prophet, entrusted with guiding humanity into the Æon of Horus. A prolific writer, he published widely—composing the "Libri" of Thelema—over the course of his life.