Brahmarupa
Mahakala is the outer form of Chaturmukha Mahakala. He is the special protector of the Guhyasamaja
Tantra and the 2nd main protector of the
Sakya School.
Brahmarupa, a benign form of the wrathful deity Mahakala, is shown as a bearded nomadic ascetic, sitting on a corpse, wearing a bone apron, and holding a thighbone trumpet and a skull cup.
A protector of the Sakya school of
Tibetan Buddhism, he is credited with introducing the
Hevajra .