Who is Rides-at-the-door from Fools Crow and what is their importance?

Rides-at-the-door is White Man's Dog father. He stands a head taller than his son and has a broad torso. He owns many horses, has three wives and speaks the language of the Napikwan. When the story opens he harbors concern for his son because White Man's Dog is depressed and timid. Gossip spreads throughout the Lone Eater's camp that his son will take the coward's way and never strike an enemy. However, no one says this directly to his face for they respect him. In his heart, he wonders if it might be true. By comparison, his younger son, Running Fisher, surpasses White Man's Dog in achievements. At age 16, his younger son already has stolen two horses from the Cutthroats and the girls notice him.