There was a reason that Macon Dead did not want his son to know his Aunt Pilate, but of course, Milkman Dead found her anyway. While Macon tried to conform to the "white" world, Pilate did not. She was an interesting, spiritual woman who had no navel and a mythology about her that drew people in with such oddities as not having a navel and keeping a bag of bones in her kitchen.
Pilate first related to Milkman the story about her and his father as children, when they spent time with Circe and killed a man in a cave. This led Milkman to explore his family roots. It also led his friend Guitar to explore the money that was supposedly still in that cave. He has a sense of family pride now, and he can escape the loneliness and unhappiness of his home.
This exploration sent Milkman, at first alone and later with Pilate, on a quest to discover his origins and to bury his grandfather. Ironically, this is the last flight either of them will take, as they are both killed by an enraged Guitar who feels as if they have both cheated him.
Pilate spreads hope and pride to a formerly careless, aimless Milkman.