After realizing she was being married off to an old man she didn't love, when she was barely out of childhood herself, she fled with her horse who happened to be a talking Narnian horse. The plan was to reach the land of Narnia. She eventually came to live in Archenland, married its Prince Cor, and thus became Archenland's queen.
The only daughter of Kidrash Tarkaan, Aravis spent her youth in the heart of Calormen. Her mother and older brother had both died from unknown causes, and her father had married an unkind woman, who made no attempt to disguise her dislike for Aravis.
Aravis's already difficult home life was rendered impossible when her father announced her engagement to Ahoshta Tarkaan, an ugly, loathsome man whom she despised: -
- "Now this Ahoshta is of base birth, though in these latter years he has won the favour of the Tisroc (may he live forever) by flattery and evil counsels, and is now made a Tarkaan and the lord of many cities and is likely to be chosen as the Grand Vizier when the present Grand Vizier dies. Moreover he is at least sixty years old and has a hump on his back and his face resembles that of an ape."
- ―Aravis (Chapter 3) [src]
Feeling she had no other option, she decided to flee on her horse and commit suicide. However, her attempt on her own life was interrupted when her horse, Hwin, began to speak: -
Taken aback on hearing the horse's pleas, Aravis thought she was now suffering hallucinations due to her fear of death. Ashamed, she attempted to stab herself again, only to have Hwin rebuke her once more, placing her own head between the girl and the dagger, and this time Aravis was so curious that she forgot about killing herself.
Hwin then revealed that she was no common mare, but a talking horse of Narnia, kidnapped in her youth. Upon hearing about Narnia, Aravis was determined to go there, and she and Hwin planned to escape Calormen.
After deceiving her family into thinking she was happy to be getting married, she escaped by drugging her stepmother's slave into sleep so that no one would notice her absence.
Aravis eventually found an old friend named Lasaraleen, a fellow Tarkheena who helped her. They eventually came to hide in the secret room of the Tisroc himself. There, they overheard a conversation between the Tisroc, Prince Rabadash and Ahoshta.
Rabadash was furious that he had been rejected by Queen Susan of Narnia, and wanted to lead a force to Narnia to capture her and force her to marry him. The plan involved conquering Archenland, a kingdom on the border of Narnia.
The Tisroc agreed, but after Rabadash left, the Tisroc told Ahoshta that it made little difference to him whether Rabadash succeeded or died.
After saying her thanks and her goodbyes to her friend, Aravis fled the city, and eventually reunited with her friends.
- "Good-bye, and I thought your dresses were lovely. And I think your house is lovely too. I'm sure you'll have a lovely life – though it wouldn't suit me. Close the door softly behind me."
- ―Aravis (Chapter 9) [src]
She told her friends about Rabadash's plans, and the four set out across the Great Desert to warn Archenland. One step ahead of Rabadash's army, they barely reached Archenland in time, but with the help of a pursuing lion, who gave the horses the extra burst of speed they needed, they succeeded. This lion used its claws to tear into Aravis' back, scaring her and Hwin.
Aravis and the horses were left behind with the Hermit of the Southern March's house, while Shasta went on ahead to warn King Lune. During her recovery, Aravis and the horses were visited by Aslan. Aslan said that he had chased them so they could reach Archenland in time, and told Aravis that he had scarred her so she would understand what her stepmother's slave went through when she was punished for the drugged sleep, into which Aravis had put her in.
Shasta, who was later discovered to be Cor, the lost son of King Lune, was able to warn the Archenlanders in time, and a combined Narnian-Archenland army defeated Rabadash at the gates of Anvard. Rabadash was captured, and later sent back to Calormen in the form of a donkey by Aslan.
Aravis accepted both Cor and Lune's offer to stay with them in Anvard.
- "Oh stop it, or we'll have a real fight. Of course I'll come."
- ―Aravis (Chaper 14) [src]
Aravis later married Cor, and became queen of Archenland when Lune died, and Cor took the throne. She was also the mother of King Ram the Great.
To her credit, Aravis was both brave and intensely loyal. However, she was also very arrogant (a possible side effect of her upbringing as a privileged Tarkheena) and at times, very manipulative.
She is also said to be an amazing storyteller, which is partly the result of her upbringing: the art of telling stories forms part of the education of the nobility.
Throughout the story, we see her grow and change to become less like a ruthless Calormene, and more like a Narnian or an Archenlander.
It is likely that C. S. Lewis meant to metaphorically represent the Christian notion that though one's social status may be great, we are all as commoners before God, in the contrast between this character and Shasta; and though one be a commoner (as the character Shasta was before discovering his true identity) we are also royalty in God's eyes.