Buchis

In Egyptian mythology, Buchis (also spelt Bakh, Buchis, and Bakha) was the manifestation of the deification of Ka (power/life-force) of the war god Montu, worshipped in the region of Hermonthis.

A wild bull was chosen and said to be the Buchis incarnation of Montu, in which role it was worshipped as such. Over time, the criteria for choosing the bull became more rigid, fixing themselves on what had been simply the general appearance of bulls in the region, being a white body and black face.