Ephialtes of Trachis

Ephialtes was a Greek renegade during the Greco-Persian Wars. Born to Eurydemus (Εὐρύδημος) of Malis, he revealed the existence of a path around the Greek coalition's position at Thermopylae to the Achaemenid Empire. His efforts allowed the Persian army to overrun the Greeks' defensive formation and thereby win the Battle of Thermopylae in September 480 BC. Ephialtes had hoped that he would be rewarded by the Persian king Xerxes I, but no such reward was bestowed upon him and he was instead forced to go into hiding when a bounty was placed on his head by the allied Greeks in their pursuit of punishing his act of treason. According to Herodotus, this bounty was collected by Athenades (Ἀθηνάδης) of Trachis approximately a decade after the second Persian invasion of Greece was repelled; the Spartans paid Athenades although his motivation for carrying out the killing apparently had nothing to do with Ephialtes' status as an outlaw.