Who is the character Set in The Egypt Game?

Set, or Seth, is an Egyptian god.  He is the god of storms, deserts, chaos, and war.  According to Egyptian mythology, Set killed and mutilated his own brother, Osiris.  Despite that horrible deed, Set is not always an evil god.  Often he is portrayed as the protector of Ra.  In all cases, Set has a human body and some kind of animal head, but the type of animal head has changed throughout the mythology.  

In the book The Egypt Game, the children use Set as an evil god.   

“Ummm,” April said. “Or else we could be evil high priestesses who are going to offer him as a human sacrifice on the crocodile altar to—what was that evil god’s name?”

“Set?”

“Yeah, that’s the one.” April jumped to her feet. Throwing up her arms, she chanted, “Almighty Set has promised his servants, the crocodile gods of the Nile, the bloody heart of the young Pharaoh, Marsh—uh, Marshamosis!” She dropped to her knees. “O mighty Set, god of evil, we hear and obey.”

The Egypt Game that the children play is make believe, and it changes and evolves with their imaginations.  Characters change as rapidly as the story line changes in order to fit the needs of the story.  That's why Set can change from being a god of evil and magic to a trickster with ray guns.  

So that was the way Set started—Set the god of evil and black magic. At first he was just supposed to be a character in that particular game, and that first day he was represented by a picture of a man with an animal’s head that Melanie drew on a piece of cardboard and tacked to the wall. But once he got started, he seemed to grow and develop almost on his own, and all out of control; until he was more than evil, and at times a lot more than Egyptian. For instance, at different times, his wicked tricks included everything from atomic ray guns to sulfur and brimstone.