All you need to know about Brahmarupa Mahakala
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 .