(Ἐφιάλτης).
1. A Malian, who, in B. C. 480, when Leonidas was defending the pass of Thermopylae, guided the body of Persians called the Immortals over the mountain path (the Anopaea), and thus enabled them to fall on the rear of the Greeks. Fearing after this the vengeance of the Spartans, he fled into Thessaly, and a price was set on his head by the Amphictyonic council. He ultimately returned to his country, and was put to death by one Athenades, a Trachinian, for some cause unconnected with his treason, but not further mentioned by Herodotus. (Her. 7.213, &c.; Paus. 1.4; Strab. i. p.20; Polyaen. 7.15.)