Polyxena was the youngest daughter of King Priam and Queen Hecuba of Troy. Achilles had felt a strong sympathy towards this Trojan princess, and he told her of his only vulnerability: his heel. With that knowledge, Prince Paris, Polyxena's brother, was able to ambush Achilles and kill him. Euripides tells us that later, after the Trojans' defeat, when the Greeks were preparing to leave Troy and return home, the winds died down and the ships could not sail. The ghost of Achilles appeared to the Greeks and said that a human sacrifice was required: Polyxena had to be sacrificed at Achilles' grave. Achilles' son, Neoptolemus, conducted the sacrifice and slit Polyxena's throat - the dramatic moment that you can see depicted in this Greek vase painting.