The Potte's lineage existed to hinder the happiness of the Malfoys, something his father had been committed to doing before the Golden Boy.
Lucius and James, those metaphors that are deliberately ignored and the destiny that is drifting away, the dream potion is just a world of two people who deceive themselves and others;
Draco and Harry were two people who could never really abandon each other. Beyond faith and within love, they made a vow that must be fulfilled even across life and death.