Mahakala (Tib. Gonpo, "Great Black One") is the most important among the many dharma-protectors mentioned in the vajrayana texts. And there are many different forms of Mahakala. There are at least six different traditions of the Six Arm Mahakala (Tib. Gonpo Chakdrukp). The most famous and well-known comes from the Shangpa Kagyu tradition and this is what is seen here. This form of the deity was introduced to Tibet by Khedrub Khyungpo Naljor in the 12th century. In the 15th century this form was also adopted by the new Geluk tradition of Je Tsongkapa and became the chief protector of that school.