The major force consistently working against Bod Owens in The Graveyard Book, by Neil Gaiman, is represented by Jack. Jack belongs to a group called Jack of All Trades. Jack is one of the five Jacks that comprise this group. Their mission is to destroy Bod's family because of a prophesy that indicated that a member of Bod's family would lead to their destruction. After his family is murdered, Bod as the sole survivor, crawls into a nearby graveyard where ghosts and ghouls care for him and educate him.
Jack presents an evil force throughout the novel. Because of the way the inhabitants of the graveyard treat Bod, we know that his life is in danger. But the novel is also a story of Bod's education. He learns much about the world of the dead, the tricks of the ghosts, and the habits of ghouls. In these lessons, Bod is often in conflict with himself. He is not sure whom to trust or fear; he at times resists instructions; and he is often reminded that he is the only mortal in a world of immortals. Eventually, we learn that the dead are helping Bod, rather than working against him, but this fact is not always evident to Bod, or to the reader.