Eli from the Book of Eli must travel from one side of Australia to the other, delivering the book to a group of Christians on the coast. He must contend with all that is in The road Warrior. To make it interesting, the Humungus and his crew want the book and will do anything to get it.
Eli is armed with his blades, his shotgun and his pistol. He has six full pistol mags and 30 shotgun shells.
Eli was good because he had God's protection. So while the Humungus, Assless Chaps Man and crew are masters of the wasteland, they can't contend with God.
Actually, "God's plan" was that the Bible be transcribed and spread to the masses - it wasn't necessarily that God needed Eli to be invincible although he did for awhile.
If you are familiar with Christian themes, Jesus when he was being arrested said that he could have summoned legions of angels for help, but did not because it wasn't part of the "plan".