The Thoth Tarot is a Tarot deck painted by Lady Frieda Harris according to instructions from Aleister Crowley. Crowley referred to this deck as The Book of Thoth, and also wrote a book of that title intended for use with the deck.
The project began in 1938 and was completed five years later in 1943, although it was not published until 1969 by O.T.O. through the efforts of Grady McMurtry X°. The entire deck is designed to be a pictoral representation of the Qabalah and especially the Tree of Life, a system of ten spheres and 22 interconnecting paths that is used to organize mystical concepts.
Crowley made several distinct changes that make this deck different from most others. Most notably he renamed several cards, for example, Strength to Lust and Judgement to Aeon. He also re-arranged the astrological and Hebrew alphabet correspondences of some cards, in accordance with his earlier book, Liber AL vel Legis:
All these old letters of my Book are aright; but צ is not the Star. (AL I:57)
The Thoth deck is a highly popular deck second only to the Rider-Waite-Smith deck, and especially famous with supposedly more advanced Tarot readers.
The painting style is very stark, vividly colored and geometric; powerful symbolism is used throughout.