Although we talk of many heroes, there have also been traitors who have betrayed our people. One such was Ephialtes, whose name has come to mean ‘nightmare’. Ephialtes of Trachis was the son of Eurydemus. He betrayed his homeland in hope of receiving a 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 in 480 BC.

As Herodotus tells us:

Xerxes was pleased by what Ephialtes promised to accomplish. He immediately became overjoyed and sent out Hydarnes and the men under Hydarnes’ command, who set out from the camp at about lamp-lighting time. This path had been discovered by the native Malians, who used it to guide the Thessalians into Phocis when the Phocians had fenced off the pass with a wall and were sheltered from the war. So long ago the Malians had discovered that the pass was in no way a good thing.

The course of the path is as follows: it begins at the river Asopus as it flows through the ravine, and this mountain and the path have the same name, Anopaea. This Anopaea stretches along the ridge of the mountain and ends at Alpenus, the Locrian city nearest to Malis, near the rock called Blackbuttock and the seats of the Cercopes, where it is narrowest.

This, then, was the nature of the pass. The Persians crossed the Asopus and travelled all night along this path, with the Oetaean mountains on their right and the Trachinian on their left. At dawn they came to the summit of the pass.

Herodotus notes that two other men were also accused of betraying this trail to the Persians: Onetas, a native of Carystus; and Corydallus, a native of Anticyra. Nevertheless, he argues that 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 of Trachis.

Ephialtes’ hope of reward from the Persians came to nothing when they were defeated at the battle of Salamis later the same year. 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 around 470 BC; but the Spartans rewarded Athenades all the same.