Ephialtes of Trachis
Ephialtes (Greek: Ἐφιάλτης, Ephialtēs; although Herodotus spelled it as Ἐπιάλτης, Epialtes) was the son of Eurydemus (Greek: Ευρυδήμος) 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 BC.
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 guard composed 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 (Greek: Αθηνάδης) of Trachis, around 470 BC, but the Spartans rewarded Athenades all the same.
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 popular media
In the 1962 film The 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 miniseries 300, the 2006 film adaptation of the same name, and the 2014 sequel, portray Ephialtes (played by Andrew Tiernan) as a severely deformed Spartan exile whose parents fled Sparta to protect him from the infanticide he would have surely otherwise suffered as a disfigured infant and, therefore, unfit warrior. Since he is unable to fight in formation, he is consigned to noncombatant duties that do not satisfy his desire for a sense of belonging, and so he defects to the Persians.
Ephialtes is used in Greek as a synonym for traitor, in a comparable fashion to the usage of the words Quisling or Judas, or Benedict Arnold in the US. However, the direct translation from Greek means nightmare.
- Battle of Traigh Ghruinneart, where a dwarf switches sides and kills the leader of the forces he originally was to fight for