As the ultimate champion, Rustam is determined to find a horse to match his own strength and stamina. After several days of searching, he spots a young colt “strong as an elephant … his hoofs of steel, his skin bright and dappled as though flecked with petals of red roses on saffron.” Rustam subdues the colt by throwing a lasso around its neck. When he asks for the horse’s price, the herdsman replies, “If you are Rustam, then mount him and defend the land of Iran. The price of this horse is Iran itself, and mounted on his back you will be the world’s savior.” He calls it Rakhsh (Thunder), a name as well known in Persian literature as that of Rustam himself.
Rakhsh’s intelligence and devotion become particularly apparent during the first of seven ordeals or heroic labors that occur when Rustam must rescue the foolhardy and impetuous king Kay-Kavus, who had been imprisoned by the White Demon in far-off Mazandaran. Overcome by fatigue on his long journey, Rustam lies down to rest. When a ferocious lion threatens to attack, Rakhsh, “boiling like water,” seizes the beast by its neck and kills it without disturbing the sleeping Rustam.