Bhairava Avatar 1

Bhairava beheaded one of Brahmas five heads and since then Brahma has only four heads. When depicted as Kala Bhairava, Bhairava is shown carrying the severed head of Brahma. Cutting off Brahmas fifth head made him guilty of the crime of killing a Brahmin(Brahmahatyapap), and as a result, he had to carry around the disembodied skull for twelve years and roam as Bhikshatana, a mendicant, until he had been absolved of the sin.