Apophis, the Destroyer.
Patron of: evil and darkness.
Appearance: a great serpent or crocodile.
Description: Apep was the ancient spirit of evil and destruction who dwelled in eternal darkness. Every day he would attempt to devour the Sun Boat of Ra as it sailed the heavens. Set's original role was to battle Apep and keep him from destroying the boat. Occasionally, Apep would succeed, and the world would be plunged into darkness (a solar eclipse?). But Set and his companion Mehen would cut a hole in Apep's belly to allow the Sun Boat to escape.
Apep commanded an army of demons that plagued mankind. Only by putting faith in the gods of light could people defeat the demons.
Every year, a ritual called the "Banishing of Apep" would be held by the priests of Ra. They would take an effigy of Apep and in the center of the temple they would pray that all the wickedness in Egypt would go into the effigy. Then they would trample the effigy, crush it, beat it with sticks, pour mud on it, and eventually burn and destroy it. In this way, the power of Apep would be curtailed for another year.