Hydarnes (Old Persian Vidarna): Persian nobleman, 0ne of the seven conspirators who killed the Magian Gaumâta and helped Darius become king (September 522 BC). Was sent against the Median rebel Phraortes in the winter of 522-521 BC. He defeated his opponent near Marush (near modern Yazd) on January 12, but was unable to pursue him and remained in Kampanda (east of Kermânshâhân). After four months, Darius came to Media with a second army, and made quick work of the rebellion.