Ephialtes is a Greek who leads Xerxes' army to an hidden path that empties behind the cursed 300 spartan soldiers during the batlle of the Hot Gates (480 B.C.).
Upon being rejected into the Spartan Army by Leonidas on account of his inability to raise his shield high enough to defend those beside him, Ephialtes defected. He beseeched Xerxes and informed the mighty king of the pass that would allow Persian troops to flank the 300 Spartans.In exchange Ephialtes would be rewarded with women and a uniform. The Persians intercept and surround the Spartans. When Ephialtes begs Leonidas to surrender peacefully Leonidas utters "May you live forever Ephialtes". The Spartans were a warrior culture, and they prized a glorious death in battle above all else. Wishing that another spartan would live forever would have been the highest insult a Spartan could issue: a curse to the Spartan dream of a glorious death on the field of battle.
Ephialtes was written about in historical accounts of the battle as one of several traitors to the Spartan army. The goat path that the Persians in order to outflank the Spartan soldiers indeed existed, and accounts demonstrate that he did just that. Ephialtes' mangled, hunchbacked appearance was most likely artistic license (there was no indication of Ephialtes actually being deformed), giving him an outward appearance that would reflect the ugliness inside.