Mnevis
In Egyptian mythology, Mnewer (also spelt Mnevis) was a manifestation of the Ka (life-force/power) of the chief god, Atum-Ra, in the region of Heliopolis. The origin and meaning of its name is currently unknown. Since the word Ka was also used to mean bull, Mnevis was identified as being a living bull. Thus, as a symbol of the sun god, Ra, the Mnevis was often depicted, in art, with a solar disc between its horns.
A suitable bull was selected from the area, and said to be the living Mnevis bull, and was taken to a special temple, where it was worshipped, and its movement used as an oracle. Since the fertile soil of the Nile was so black that the word for black (Khem) became the Egyptian word for Egypt, and bulls in this region had a tendency to black colouring, the bull selected to be the Mnevis was traditionally completely black, thus being referred to as Kemwer, meaning great black (one). When a completely black bull could not be found, they chose one that was completely white, in contrast.
Eventually, it became identified as another form of the increasingly more popular Apis, which had become considered an avatar of Osiris.