The main characters in The Horse and His Boy are:
Shasta (Prince Cor) - He is the elder twin brother of Prince Corin of Archenland. He was kidnapped and adopted in Calormen by a fisherman named Arsheesh. He later overheard plans to sell him as a slave and decided to escape to Narnia. The boy discovered a plot by Prince Rabadash to attack Archenland through Aravis and proceeded to warn the King of the impending attack.
Bree - He is a talking horse kidnapped from Narnia and held captive in Calormen. The horse falls in the same predicament as Shasta and joins him in the escape to Narnia.
Hwin - This is a talking mare who is on the run with her wealthy rider, Aravis. Hwin and Aravis join Bree and Shasta in their escape.
Aravis - She is the daughter of a wealthy Tarkaan and also on the run with the hopes that she will arrive to a country where her individual rights are respected. Aravis overheard Rabadash’s plot while hiding in their palace and informed Shasta.
Rabadash - This is the evil Prince of Calormen. He was defeated by the Narnian army and later turned into a donkey by Aslan the mighty lion. He was only able to maintain his human form while in Calormen and this prevented him from attacking his neighbors.