Achelous tells Theseus about fighting with Hercules over Deianira’s hand in marriage. Achelous’s attempts at persuasive speech are ineffective, and Hercules breaks off Achelous’s horn. The narrator jumps to the story of a centaur, Nessus, who attempts to rape Deianira. Hercules prevents the rape by shooting Nessus with an arrow. Just before he dies, Nessus gives Deianira a poisonous cloak, telling her it is a love charm. Later, worried that her husband Hercules no longer loves her, Deianira gives him the cloak. He puts it on and dies a protracted, painful death. Jupiter, with the assent of the gods, deifies Hercules.
Hercules’ mother, Alcmene, and Iole, Alcmene’s daughter-in-law, relate tales of sorrow. Alcmene says that Juno and Lucina, the goddess of childbearing, kept her in labor for seven days and nights until her servant girl, Galanthis, found a way to help her. Iole says her half-sister, Dryope, plucked a lotus plant to give to her baby. The plant, which was once a nymph, began to bleed. Dryope was slowly transformed into a tree as punishment.
The narrator offers two unusual stories of love. Byblis is in love with her twin brother, Caunus. When she realizes this love is unnatural and socially unacceptable, she tries to rationalize it by thinking of gods who have sex with their sisters. Her brother rejects her overtures and flees. Byblis tries to find him, and when she fails her weeping turns her into a spring. The second story concerns Iphis. Ligdus, an honest Cretan man, tells his wife, Telethusa, that if their infant is a girl she must be left outside to die. Telethusa cannot bear to do this, so she makes Ligdus believe that Iphis is a boy. When Iphis is thirteen, a marriage is arranged between her and a girl named Ianthe. The two girls fall in love. Telethusa prays to Isis for a miracle. Isis answers her prayer and, to the delight of Telethusa and Iphis, transforms Iphis into a young man.
At first glance, the two clashes in Book IX seem to suggest that brains are no match for brawn. Achelous’s eloquence seems useless. His fine words only anger Hercules. With his superior strength, Hercules easily defeats both Achelous and Nessus, breaking the horn of the former and killing the latter. However, an alternate interpretation of these contests is possible. Hercules may win the battles, but he does not win the war. Achelous has an embarrassing tale of a broken horn to tell, but at least he is still alive to tell it. And although Nessus loses his own life, he ensures the death of Hercules. With great cunning, he deceives Deianira into poisoning her own husband. In one way, Nessus’s victory over Hercules is more satisfying than Hercules victory over him, since Nessus causes Hercules’ own wife to do the dirty work for him.
With the stories of Byblis and Caunus and Iphis and Ianthe, Ovid examines love from a social and biological point of view. Byblis reasons that while her love for her twin brother is unnatural from a social point of view, its heterosexuality makes it natural from a biological point of view. Iphis and Ianthe suffer from a different dilemma. Society accepts their love for each other, but only because its homosexual nature is hidden. By juxtaposing these love stories, Ovid invites us to compare them and think about why one love affair fails and the other succeeds. One possibility is that Iphis’s and Telethusa’s respect for social mores leads to their happiness. Instead of flying in the face of conventionality, as Byblis does, they accept society’s restrictions. They assume that it will be easier to achieve a miracle than to be open about Iphis’s homosexual love for Ianthe. Iphis may also find happiness because of her respect for the gods. Byblis relies on herself, chasing after her brother without seeking help. Iphis’s mother, on the other hand, prays to Isis for aid.
In Ovid's version, Perseus does *not* use the head of Medusa to kill the sea monster. After flying up and stabbing it in the shoulder, he then swoops down to a rock and stabs it repeatedly: "His left hand on a ridge, and with his sword stabbed time and time again the monster's groin" (IV.732 -- 33). Immediately after, Andromeda is released and they marry. This conflicts with the analysis, also, that he's not brave or heroic enough to face the creature using his own arms rather than just the Gorgon's head.