Eric is a teenage Demonalogist Hacker in the novel
Faust Eric. He attempts to summon a demon to grant him three wishes: to rule a kingdom, get a girl and live forever. Easy enough for the average demon.
Unfortunately, what he gets is Rincewind, who is not a demon. While he may be summoned and suffer all the potential maladies that come with being a demon (a proverbial chain, a circle that burns him), he can't actually snap his fingers and make wishes come true at will.
Surprisingly, because of his luck or the state he'd come to Eric as, it works; but only if it can be warped to the demon's specifics: "Grant the wish, but don't." So follows are the are mis-adventures of Eric, Rincewind, a Parrot who's mastered the word 'wossname', and Rincewind's Luggage. Along the way, they'll attempt to keep history...history without actually distorting it. Tsort, Tezumen, and Ephebians all have a part to play and as it turns out, Eric's dreams of immortality just don't pan out like he'd thought it would.