bore a son, whom they named Achilles. It was foretold that he would either die of old age after an uneventful life, or die young in a battlefield and gain immortality through poetry. Furthermore, when Achilles was nine years old, Calchas had prophesied that Troy could not again fall without his help. A number of sources credit Thetis with attempting to make Achilles immortal when he was an infant. Some of these state that she held him over fire every night to burn away his mortal parts and rubbed him with ambrosia during the day, but Peleus discovered her actions and stopped her. According to some versions of this story, Thetis had already killed several sons in this manner, and Peleus' action therefore saved his son's life. Other sources state that Thetis bathed Achilles in the Styx, the river that runs to the underworld, making him invulnerable wherever he was touched by the water. Because she had held him by the heel, it was not entirely immersed during the bathing and thus the heel remained mortal and vulnerable to injury (hence the expression "Achilles' heel" for an isolated weakness). He grew up to be the greatest of all mortal warriors. After Calchas' prophecy, Thetis hid Achilles in Skyros at the court of King Lycomedes, where he was disguised as a girl. At a crucial point in the war, she assists her son by providing weapons divinely forged by Hephaestus (see below). Elopement of Paris and Helen The most beautiful woman in the world was Helen, one of the daughters of Tyndareus, King of Sparta. Her mother was Leda, who had been either raped or seduced by Zeus in the form of a swan. Accounts differ over which of Leda's four children, two pairs of twins, were fathered by Zeus and which by Tyndareus. However, Helen is usually credited as Zeus' daughter, and sometimes Nemesis is credited as her mother. Helen had scores of suitors, and her father was unwilling to choose one for fear the others would retaliate violently. Finally, one of the suitors, Odysseus of Ithaca, proposed a plan to solve the dilemma. In exchange for Tyndareus' support of his own suit towards Penelope, he suggested that Tyndareus require all of Helen's suitors to promise that they would defend the marriage of Helen, regardless of whom he chose. The suitors duly swore the required oath on the severed pieces