Ka is what the ancient egyptians called the soul in heaven. Which was similar to a spirit or angel. There was a hieroglyph of the Ka which was simply a pair of arms raised up. In ancient egypt there were Ka-Priests who basicly lived in the tombs and gave the ghosts of the dead sacrifices so that they can survive for a long time after death. They thought that the ghost or Ka of the deceased needed food and drink. My personal theory is that this belief was fabricated in order to teach the priests the art of sympathetic magick and discipline, which are both obtained by serving the sacrifices of food and drink to the Ka of the dead.