The profusion of divine and mortal personages that populate the Iliad‘s mythological context can be confusing. It helps to group the Iliad‘s myths into two intermingling streams, one leading to Achilles; the other, to the Trojan War.
One group features the perspective of a favored daughter, Thetis, who becomes a mother of a hero, Achilles; the other, the perspective of a wife, Hera, insulted by her husband Zeus’s philandering, who enlists various sons in attempts to get revenge–but whose anger Zeus cleverly deflects from himself to the Trojans. In both sets of myths, fathers favor daughters over wives, and mothers favor sons over husbands.
I. Stream leading to Achilles:
When she is being raised as a daughter in Zeus’s house, Zeus desires Thetis more than his wife.
Fearing overthrow by her son, Zeus subjects Thetis to an inferior marriage–to a mortal no less.
Thetis becomes the mother of Achilles–and attempts simultaneously to burn away and immortalize his “mortal part.”
In parallel myths Demeter interrupts her search for her daughter, Persephone–also favored by Zeus over Hera and forced into an inferior, strategic marriage–to nurture the mortal hero, Demophoon.
II. Stream culminating in the Trojan War:
No longer (simply) the architect a just order, based on mutual respect, in Hesiod’s Theogony, Zeus in the Iliad and its background myths is a philandering husband who keeps his wife, Hera, in a perpetual state of sexual insult, envy, and vengeful anger.
Through the clever device of the Judgment of Paris, Zeus deflects his erotically insulted wife’s anger onto mortal substitutes, the Trojans who harbor Paris, the mortal deputized by Zeus to judge his wife less beautiful and desirable than (in the Iliad tradition) his daughter, Aphrodite.
Achilles is the glorious surrogate son whom Hera could never produce on her own–and her chief avenger against the the Trojan stand-ins for Zeus.