Nor did the vengeance of the successful conspirators stop here.  Speeding to the capital, with the head of the Magus in their hands, and exhibiting everywhere this proof at once of the death of the late king and of his imposture, they proceeded to authorize and aid in carrying out, a general massacre of the Magian priests, the abettors of the later usurpation.  Every Magus who could be found was poniarded by the enraged Persians; and the caste would have been well-nigh exterminated, if it had not been for the approach of night.  Darkness brought the carnage to an end; and the sword, once sheathed, was not again drawn.  Only, to complete the punishment of the ambitious religionists who had insulted and deceived the nation, the day of the massacre was appointed to be kept annually as a solemn festival, under the name of the Magophonia; and a law was passed that on that day no Magus should leave his house.

The accession of Darius to the vacant throne now took place (Jan. 1, B.C. 521).  According to Herodotus it was preceded by a period of debate and irresolution, during which the royal authority was, as it were, in commission among the Seven; and in this interval he places not only the choice of a king, but an actual discussion on the subject of the proper form of government to be established.  Even his contemporaries, however, could see that this last story was unworthy of credit and it may be questioned whether any more reliance ought to be placed on the remainder of the narrative.  Probably the true account of the matter is, that, having come to a knowledge of the facts of the case, the heads of the seven great Persian clans or families met together in secret conclave and arranged all their proceedings beforehand.  No government but the monarchical could be thought of for a moment, and no one could assert any claim to be king but Darius.  Darius went into the conspiracy as a pretender to the throne:  the other six were simply his “faithful men,” his friends and well-wishers.  While, however, the six were far from disputing Darius’s right, they required and received for themselves a guarantee of certain privileges, which may either have belonged to them previously, by law or custom, as the heads of the great clans, or may have been now for the first time conceded.  The king-bound himself to choose his wives from among the families of the conspirators only, and sanctioned their claim to have free access to his person at all times without asking his permission.  One of their number, Otanes, demanded and obtained even more.  He and his house were to remain “free,” and were to receive yearly a magnificent kaftan, or royal present.  Thus, something like a check on unbridled despotism was formally and regularly established; an hereditary nobility was acknowledged; the king became to some extent dependent on his grandees; he could not regard himself as the sole fountain of honor; six great nobles stood round the throne as its supports; but their position was so near the monarch that they detracted somewhat from his prestige and dignity.