Achilles, in Greek mythology, son of the mortal Peleus, king of the Myrmidons, and the Nereid, or sea nymph, Thetis. Achilles was the bravest, handsomest, and greatest warrior of the army of Agamemnon in the Trojan War. According to Homer, Achilles was brought up by his mother at Phthia with his cousin and inseparable companion Patroclus. One of the non-Homeric tales of his childhood relates that Thetis dipped Achilles in the waters of the River Styx, by which means he became invulnerable, except for the part of his heel by which she held him—the proverbial “Achilles’ heel.”
The later mythographers related that Peleus, having received an oracle that his son would die fighting at Troy, sent Achilles to the court of Lycomedes on Scyros, where he was dressed as a girl and kept among the king’s daughters (one of whom, DeĂŻdamia, bore him Neoptolemus). Hearing from the soothsayer Calchas that Troy could not be taken without Achilles, the Greeks searched for and found him.  During the first nine years of the war, Achilles ravaged the country around Troy and took 12 cities. In the 10th year a quarrel with Agamemnon occurred when Achilles insisted that Agamemnon restore Chryseis, his prize of war, to her father, a priest of Apollo, so as to appease the wrath of Apollo, who had decimated the camp with a pestilence. An irate Agamemnon recouped his loss by depriving Achilles of his favourite slave, Briseis. Â
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