The Seven Trials of Rostam
هفت خان رستم
The king got himself captured by demons. Somebody had to go.

Kay Kavus, who has never had an idea worth acting on, invades Mazandaran on the strength of a song about how nice it is there. His army is destroyed and blinded by the White Demon, and the king is in a cave.
Rostam goes after him alone, by the short road, which takes seven days and holds seven trials. A lion attacks while he sleeps and his horse Rakhsh kills it without waking him. A desert nearly finishes them both, until a ram walks past and leads them to water. A dragon appears three times, and twice Rakhsh wakes him and the dragon vanishes and Rostam swears at the horse; the third time he sees it. A sorceress in the shape of a beautiful woman. A warrior named Owlad, whom he catches in his lasso and turns into his guide. Arzhang, who commands the demons. And then the White Demon, asleep in the dark of the cave.
He kills it, and uses its blood to restore the sight of the blinded army and the king: the same king who caused all of it, and whom he will keep rescuing for another century.
Why it matters
The most-illustrated sequence in the entire manuscript tradition. Every workshop for a thousand years painted Rakhsh fighting the lion. It is also where the poem's real relationship gets set: Iran's greatest hero, permanently in service to fools.