How does the author contrast the characters of Sallah and Avril in the novel, Dragonsdawn?

In the third dyad, McCaffrey contrasts Sallah Telgar and Avril Bitra, doubling the impact of an almost archetypal theme from pioneering life and tales: the expulsion from Eden.

While both women are strong-bodied and good strategists, their motivations and ambitions are violently opposed.

The colonists have discovered the serpent in the garden—Thread—and lose their Edenic illusions of Pern; Bitra becomes the second serpent. She brings to Pern her Earthly sense of greed and seduces men to get power and gemstones.