The Ordo Templi Orientis (Order of Oriental Templars) is a fraternal organization with a series of graded mystery initiations. It was the first of the great orders to accept the Law of Thelema as it is described in Liber AL vel Legis. Its aim is to promote this law as the standard of human conduct and understanding. Its initiations convey life lessons that aid the initiates in their everyday lives.
A Brief History of the O.T.O.
Somewhere around the end of the 19th and the very beginning of the 20th century, Karl Kellner and Theodor Reuss , two German irregular Freemasons decided to bring the so-called "high grades", rites outside of the basic Blue Lodge Freemasonry to Germany. They acquired papers for several of these grades, and started out as Academia Masonica. Kellner died in 1905, leaving Reuss in charge. As more and more Freemasons in Germany became affiliated with the English and French Grand Lodges, he had to leave, and he settled in England, renaming the Academia to Order of Oriental Templars and Esoteric Rosicrucians.
When McGregor Mathers, the then head of the Golden Dawn sued Aleister Crowley in 1907 for publishing their materials, the former claimed to be the leader of all Rosicrucians, causing hundreds of other self-proclaimed Rosicrucian leaders, to contact Crowley. Reuss initiated him into the Order.
In 1912 Crowley published his Book of Lies, and Reuss confronted him for supposedly publishing the secrets of the highest degrees of the Order (even though Crowley was not at that grade, therefore he could not have known). When it was proven that Crowley knew this from his own experience, Reuss gave him to IX°, and appointed him National Grand Master General of the English section of the O.T.O., which Crowley decided to name Mysteria Mystica Maxima, or M.M.M.
In 1913 he wrote the Gnostic Mass, which Reuss translated to German and accepted as the central rite of the Order.
During WWI Crowley lived in the USA, where, after some failed attempts to get the Freemasonic O.T.O. going, he reworked the initiations to reflect Thelemic teachings. In 1920 Reuss had a stroke and Crowley took over as Outer Head of the Order, a decision that was later ratified by the remaining high degree members in 1925.
Crowley died in 1946. He was succeeded by Frater Saturnus and later Hymenaeus Alpha as O.H.O. The current Outer Head of the Order is Hymenaeus Beta.