 When he is asked to recall being owned by a powerful necromancer (having erased most related memories, and sealed away what he couldn't erase), he is reluctant to do so.Unlocking said memories changes him, making him arrogant and very powerful, and he nearly kills Harry, who saves himself only by tricking Bob into reverting to normal.Bob tends to be very stubborn about providing help unless Harry pays him, in the form of spicy romance novels and occasional time out of the skull.