Catch

Satan himself, sitting on his throne in the great city of Pandemonium, had spoken to a multitude of hellish hosts, "In our exile, we must be beholden unto Jehovah for two things: one, that we exist, and two, that Catch has no ambition."

Catch is a demon who appears in Christopher Moore's novels. He is a central character in  Practical Demonkeeping,  and also makes an appearance in  Lamb: The Gospel According to Biff, Christ's Childhood Pal.

Catch is a fallen angel, formerly a warrior Seraph. In ancient times, he was summoned up by King Solomon to build his temple, but he amused himself by killing Solomon's slaves, and eventually broke free to wreak havoc on Solomon's household. Solomon had a Djinn, Gian Hen Gian, chain Catch to a stone, where a giant owl repeatedly tore out his liver and ate it. During the lifetime of Jesus, Catch was bound to the sorcerer Balthasar, granting him immortality until he broke free and was banished back to hell. In the early 20th century, he was summoned again by a young man named Travis O'Hearn, who spent the following seventy years trying to figure out how to get rid of him.

Catch is a reptilian creature. In his normal form, Catch is about the size of a child, and is invisible to most people. When eating or out of control, however, he becomes a massive brute. Catch can be summoned and bound; whoever is bound to him becomes immortal and ageless for the duration of the pact, but quickly returns to their true age if it is broken. He cannot harm his summoner, but must eat humans regularly or he'll become cranky.