Role: God of chaos, evil, the desert, war, violence, conflict, and sandstorms (all bad things!)
Appearance: Form of a man, with the head of an unidentified donkey-like animal. He was sometimes seen as a pig or a hippo.
Sacred animal: the mythical "Set animal" (see below)
Relations with other gods: Nut (mother); Geb (father); Osiris (brother), Isis and Nephthys (sisters)
One of the recurring themes in ancient Egyptian culture is duality— everything appearing in opposite pairs. Upper Egypt and Lower Egypt, papyrus and lotus, cobra and vulture, Isis and Nephthys. Look at a typical mummy like this one and you'll notice how the images are symmetrically paired on the left and right. And it wasn't just on mummies, either. Spend some time looking at Egyptian art and architechture and you'll see how this "two-ness" was everywhere!
Such was the case with the constant battle of good vs. evil, as represented by Horus and Set. According to Egyptian mythology, jealous Set murdered his brother Osiris in order to seize the throne. Osiris's son Horus avenged his father's death by battling Set in a bloody war that lasted for a very long time. The fight was only finally settled by a panel of gods: They ruled that Set must be punished so it became his job to travel with Re in his sun boat as it sailed across the sky, standing ready to protect the sun from the Apophis serpent (a giant evil snake that threatened to disrupt the daily journey of the sun).