Ephialtes was the son of Eurydemus of Malis. He betrayed his homeland, in hope of receiving some kind of reward from the Persians, by showing the Persian forces a path around the allied Greek position at the pass of Thermopylae, which helped them win the Battle of Thermopylae in 480 BCE.
Betrayal
The allied Greek land forces, which Herodotus states numbered no more than 4,200 men, had chosen Thermopylae to block the advance of the much larger Persian army. Although this gap between the Trachinian Cliffs and the Malian Gulf was only "wide enough for a single carriage", it could be bypassed by a trail that led over the mountains south of Thermopylae and joined the main road behind the Greek position. Herodotus notes that this trail was well known to the locals, who had used it in the past for raiding the neighboring Phocians. The Persians used the trail to outflank the defenders. Spartan king Leonidas sent away most of the Greeks, but he himself remained behind with a rear guardcomposed of his men, the Thespian contingent and a Theban detachment. Ephialtes expected to be rewarded by the Persians, but this came to nothing when they were defeated at the Battle of Salamis. He then fled to Thessaly; the Amphictyons at Pylae had offered a reward for his death. According to Herodotus, he was killed for an apparently unrelated reason by Athenades of Trachis, around 470 BC, but the Spartans rewarded Athenades all the same.
Others
Herodotus notes that two other men were accused of betraying this trail to the Persians: Onetas, a native of Carystus and son of Phanagoras; and Corydallus, a native of Anticyra. Nevertheless, he argues Ephialtes was the one who revealed this trail because "the deputies of the Greeks, the Pylagorae, who must have had the best means for ascertaining the truth, did not offer the reward on the heads of Onetas and Corydallus, but for that of Ephialtes."
In the 1962 filmThe 300 Spartans, Ephialtes was portrayed by Kieron Moore and is depicted as a loner who worked on a goat farm near Thermopylae. He betrays the Spartans to the Persians out of greed for riches, and, it is implied, unrequited love for a Spartan girl named Ellas. Frank Miller's 1998 comic book miniseries300, the 2006 film adaptation of the same name, and the, portray Ephialtes as a severely deformed Spartan exile whose parents fled Sparta to protect him from the infanticide he would have surely suffered as a disfigured infant. Although he is brave and his spear thrust more than adequate, he can not raise his arm so he can be part of the phalanx. Leonidas asks him to support his brethren by bringing the wounded water and clearing the dead from the battleground. In anger, Ephialtes swears to prove his parents and him wrong and betrays them to Xerxes by revealing the hidden path in return. When only a handful of Spartans are left when the Persians descend, Ephialates is with them. Leonidas wishes him to live forever, which is an insult to a Spartan since he will not have died with honor in battle.
Name
After the betrayal of Ephialtes, the name "Ephialtes" received a lasting stigma; it came to mean "nightmare" in the Greek language and to symbolize the archetypal traitor in Greek culture.
