Ephialtes enters history as a local man with dangerous knowledge. Herodotus calls him the son of Eurydemus and identifies him as a Malian. He came from the region around Trachis, a city of Malis south of Thessaly and west of the pass. His father, social position, occupation and education are unknown. His importance arose entirely from geography. He knew the Anopaea path, and that knowledge gave a humble local the power to change the course of a war.

Thermopylae, the Hot Gates, was a narrow corridor between the cliffs of Mount Callidromus and the Malian Gulf. In 480 BCE the Greek army under Leonidas of Sparta occupied the pass because its narrow width prevented the Persian army from deploying its numerical strength. Herodotus describes a causeway in places barely wide enough for a single wagon. The Greeks could stand in a line only a few men deep and use the terrain as a fortress.

The pass was not the only route. Behind it, a mountain path ran from the Asopus River along the ridge called Anopaea and descended behind the Greek position near Alpenus, the first Locrian town south of Malis. Herodotus says the Malians had discovered the path and once used it to guide the Thessalians against the Phocians when the Phocians had fortified Thermopylae. The path was therefore not a secret in an absolute sense. It was a local route known to people familiar with the mountains. What Ephialtes supplied was not the discovery of an unknown trail but the willingness to reveal it to Persia at the decisive moment.

For two days the Persian army attacked the pass and failed. Xerxes' infantry could not break the Greek line. Herodotus says the king watched his troops suffer and even leapt from his throne in alarm. On the third day, Ephialtes came to Xerxes. Herodotus gives his motive directly: he expected a very great reward. He told the king about the path over the mountain and offered to guide the Persian force himself.

Herodotus records an alternative accusation. Some said that Onetas, son of Phanagoras of Carystus, and Corydallus of Anticyra had shown the way. He rejects the story because the Pylagorae, the Amphictyonic deputies who should have known the truth, offered a reward for Ephialtes rather than for the other men. Ephialtes also fled Greece, confirming his fear of punishment. Even in Herodotus, therefore, the identity of the guide rests not on a surviving eyewitness transcript but on public tradition, official bounty and the suspect's flight.

Xerxes accepted the offer and sent Hydarnes, the Persian commander, with the force later known as the Immortals. They left the camp at night and followed Ephialtes into the mountains. The path ran from the Asopus through wooded slopes along the ridge of Anopaea. Herodotus says the whole mountain was covered with oak trees. Because the air was still, the sound of Persians moving through the leaves alerted the Greek guards above.

Those guards were one thousand Phocians. They had volunteered to defend the path and protect their own country from the mountain side. They were not expecting the main Persian attack. When they heard the rustling and saw armed men emerging from the trees, they rushed to take up their weapons. Hydarnes was startled and asked Ephialtes whether these troops were Lacedaemonians. Ephialtes told him the truth: they were Phocians. Hydarnes ordered his archers to shoot and moved on rather than waste time in a mountain fight. The Phocians imagined that they were the Persians' target and retreated to the crest, allowing the column to pass.

By dawn Hydarnes and his men had reached the height above the Greek rear. Scouts from the pass brought the news to Leonidas. The Greeks now faced encirclement. The strategy that had neutralised Persian numbers was finished. Leonidas sent away most of the allied contingents while the Persians were still descending. The Spartans remained, together with the Thespians under Demophilus and the Theban contingent. The Phocians climbed down from the mountain after the Persians had passed and did not join the last battle in the pass.

The betrayal did not kill the Greeks by itself. Leonidas could have withdrawn with most of his army. Instead, he chose to remain, probably to cover the retreat and to fulfil the Spartan understanding that a king and his guard must not abandon the post. Ephialtes created the encirclement, but the final sacrifice was a decision made by the defenders. At sunrise Xerxes advanced. The Greeks fought outside the narrowest part of the pass, killed many Persians and later withdrew behind the wall and the hill where the lion monument to Leonidas would later stand. When Hydarnes and Ephialtes appeared from the mountain, the Persians attacked from front and rear. The Greeks resisted until their spears and swords broke and Xerxes ordered his archers to bury them beneath arrows.

The name of Ephialtes therefore stands at the hinge between tactical fact and moral memory. The Persian army needed a flanking movement. The Malians and other locals knew the terrain. The path could have been found by scouts, guides or interrogated inhabitants. Herodotus nevertheless presents Ephialtes as the individual whose greed supplied the answer. Whether he was the indispensable traitor or the man whom tradition fixed with responsibility, the effect was the same. The Greek line collapsed.

Ephialtes' reward never made him secure. Herodotus does not say that Xerxes paid him, and later tradition gives no evidence of lasting Persian patronage. After the invasion, fear of the Lacedaemonians drove him into exile in Thessaly. When the Amphictyons assembled at Pylae, the Greek deputies set a price on his life. He lived as an outlaw while the Greeks rebuilt their cities and defeated Xerxes at Salamis and Plataea.

Years later Ephialtes returned to Anticyra. There Athenades of Trachis killed him. Herodotus says Athenades acted from another cause, not the betrayal, although the lost portion of his history apparently explained the personal motive. The Lacedaemonians honoured Athenades anyway. The Spartan state had not forgotten Thermopylae, and the killer of Ephialtes received public approval even if the immediate reason for the killing was private. The date is uncertain, but around 470 BCE is commonly proposed.

No ancient source gives Ephialtes a redemption. No hero cult, family tradition or political defence survives. His father is named, but no wife, children, office or achievement beyond the betrayal appears. Unlike Demaratus, the exiled Spartan king who served Persia and retained a complex historical voice, Ephialtes remains a one-act figure. He knows the path, sells the path, guides the Persians, flees and dies.

The historicity of his role requires caution. Herodotus wrote about two generations after the battle, and his Thermopylae narrative combines military detail, commemorative tradition and moral drama. The alternative suspects Onetas and Corydallus may preserve confusion among local guides. Recent scholarship has even questioned whether Xerxes depended entirely upon Ephialtes. Persian commanders had experience in mountain warfare and scouts, and the path was known locally. They may already have understood that the position could be turned. Ephialtes could have been the guide who confirmed the route, while later Greek memory made him the sole author of catastrophe.

The debate does not erase his historical function. Greek tradition needed a named traitor because Thermopylae was too important to be lost by geography alone. The defenders had chosen a perfect position. The Persians had seemed impossibly strong. The Greek failure demanded a human explanation, and Ephialtes supplied it. His local knowledge became betrayal, his name became a moral category and his act became the reason the three hundred died.

The Greek word ephialtes was already a noun before the traitor became famous. It could mean nightmare or the demon that leapt upon a sleeper. Later readers found the meaning irresistibly appropriate. The man who came upon the Greeks from behind bore the name of a night terror. Whether this linguistic coincidence was ancient wordplay or later interpretation, it deepened the legend.

His presence in later accounts is thin. Pausanias describes the monuments and landscape of Thermopylae but adds no new details about his life. Diodorus gives a compressed narrative of the battle in which the flanking movement remains central. Strabo discusses the geography of the pass and the surrounding peoples. The main tradition remains Herodotus, and every later version ultimately returns to him.

Modern popular culture has made Ephialtes far more vivid and far less historical. In Frank Miller's 300 and its film adaptation, he is a deformed Spartan outcast whose family fled Sparta to save him from exposure. He betrays Leonidas after rejection and the promise of wealth and women. The character is a fiction. No ancient source describes Ephialtes as Spartan, deformed or rejected. The real Ephialtes was a Malian local who knew a mountain path. The invented Ephialtes expresses modern anxieties about disability, loyalty and belonging, but it should not contaminate the historical record.

The modern Ephialtes also inherits a moral simplification. Thermopylae has become the story of three hundred Spartans, and the traitor has become the sole explanation for their death. That memory omits the Thespians, Thebans, Helots, Phocians and other allies. It also omits the strategic context. The pass was meant to delay Persia while the Greek fleet fought at Artemisium and while Athens prepared evacuation. Leonidas' last stand served the larger war even though the position fell. Ephialtes ended the defence at Thermopylae, but he did not win the Persian War.

His story endures because it is compact. A local man approaches a king. A hidden path replaces force with knowledge. A price is set. A fugitive returns. A killer collects honour. The episode contains greed, betrayal, geography, punishment and memory in a few ancient chapters. It also preserves the landscape: Asopus, Anopaea, Alpenus, Anthela and Anticyra remain attached to his name.

The accurate record of Ephialtes' life is therefore both certain and incomplete. He was the son of Eurydemus, a Malian from Trachis. In 480 BCE he revealed and guided the Anopaea path to Xerxes, enabling Hydarnes to outflank Leonidas. He expected reward, received no secure place at the Persian court and fled to Thessaly. The Amphictyons set a bounty on his head. Around 470 BCE Athenades of Trachis killed him at Anticyra for a separate reason, and the Lacedaemonians honoured Athenades. No other work, office, family or exploit can be assigned to him.