Aravis is a young Tarkheena, a female member of the ruling class of Calormen. With her horse, Hwin, who is revealed to be a talking beast from the land of Narnia, she flees from her home, in order to escape an arranged marriage which is repugnant to her. Aravis is a strong character, whose confidence, bravery and loyalty are offset by arrogance and self-centeredness. On their journey north to freedom in Narnia, they fall into company with the talking stallion, Bree, and the boy Shasta. Aravis overhears a plot by the Calormenes to invade Archenland and Narnia, and with this intelligence the four companions are able to warn the Archenlanders in time to thwart the invasion. In the process of their adventures, through a series of "lessons" and encounters, Aravis's character is transformed, and she acquires humility and sensitivity. Her companion, Shasta, is discovered to be the lost heir to the kingdom of Archenland, and, upon reaching adulthood, he and Aravis marry, and rule as king and queen. They are the parents of Ram the Great, the "most famous of all the kings of Archenland".
Aravis has spent her youth in the heart of Calormen, apparently in Calavar, the province over which her father is lord. Her mother and older brother have both died and her father has recently married an unkind woman, who makes no attempt to disguise her dislike for her stepdaughter. She also has a younger brother who is "but a child". Aravis' already difficult home life is rendered impossible when her father announces her engagement to Ahoshta Tarkaan, a wealthy but unpleasant courtier whom she despises. In response she decides to commit suicide. However, her mare, Hwin, reveals herself as a Talking Horse from Narnia and persuades her to flee to Narnia instead.
As the two ride through Calormen, they meet Bree and Shasta, the eponymous horse and boy, who are also escaping to Narnia. The four try to traverse Tashbaan undetected, but they get separated and Aravis meets her friend Lasaraleen. Aravis and Lasaraleen explore the Tisroc's palace, and accidentally overhear a plan by the Tisroc and Prince Rabadash to invade Archenland. When she meets Shasta and the horses again, they agree they must urgently warn Narnia and Archenland.
As they near the border of Archenland, they are chased by a lion (later revealed to be Aslan), who claws Aravis' back in admonition for her past cruelty to her slave. Her wounds force her to remain with the Hermit of the Southern March while Shasta goes alone to complete the mission. She watches the battle through the Hermit's magic pool, appalled at the danger that Shasta faces. While in the Hermit's home, Aravis encounters Aslan, an event that changes her.
Marrying Shasta (or rather, Prince Cor), she becomes a princess of Archenland (later queen) and the mother of King Ram the Great. She is last seen in The Last Battle, and is present at the Great Reunion in Aslan's Country.