Ephialtes in Harpers Dictionary of Classical Antiquities

An Athenian statesman, a friend and partisan of Pericles, whom he assisted in carrying his political measures. He was instrumental in abridging the powers of the Areopagus-a measure assailed by Aeschylus in his Eumenides. Ephialtes thus made himself so obnoxious to the aristocratic party that his enemies had him assassinated, probably in the year B.C. 456.