The Sepher Yetzirah is one of the main and most important works of Kabbalah.
It is one of the most integral works from which such types of occultism stem..
Among other concepts it expounds the concept of Creation via the three mothers
Alef, Mem, and Shin, and their relative powers.
Referenced by other works such as the Bahir, it is broken apart into a series of statements on the Hebrew alphabet and numeric systems.
The Sepher Yetzirah is one of the main and most important works of Kabbalah