HYSTASPES (the Greek form of the Persian Vishtdspa). (I) A semi-legendary king (kava), praised by Zoroaster as his protector and a true believer, son of Aurvataspa (Lohrasp). The later tradition and the S/iahname of Firdousi make him (in the modern form Kai Gushtasp) king of Iran. As Zoroaster probably preached his religion in eastern Iran, Vishtaspa must have been a dynast in Bactria or Sogdiana. The Zoroastrian religion was al ready dominant in Media in the time of the Assyrian king Sargon (c. 715 B.c.), and had been propagated probably in much earlier times (cf. PERSIA) ; the time of Zoroaster and Vishtaspa therefore may be put at c. B.C. (2) A Persian, father of Darius I., under whose reign he was governor of Parthia, as Darius himself mentions in the Behistun inscription (2. 65). By Ammianus Marcellinus, xxiii. 6. 32, and by many modern authors he has been identified with the protector of Zoroaster, which is impossible for chronological and historical reasons, and from the evidence of the development of Zoroastrianism itself (see PERSIA : Ancient His tory) .