Bagoas was a powerful Persian minister who had the Emperors Artaxerxes III and Arses murdered before finally being killed by Darius III.
The name Bagoas is a Greek version of an Old Persian name for eunuchs. He came to prominence as a minister of Artaxerxes III, the last successful Achaemenid emperor of Persia. Bagoas also cooperated with Mentor of Rhodes, a key supporter of the Persians.
In 343 Artaxerxes led the successful Persian re-conquest of Egypt, which had rebelled sixty years earlier and fought off several Persian attacks. The Pharaoh Nectanebo II was defeated at Pelusium in the Nile Delta, ending the 30th Dynasty and with it Egyptian independence. Artaxerxes was said to have killed the sacred Apis bull in person, and the Egyptian temples were plundered of their wealth and many religious artefacts. Bagoas is said to have made a fortune by selling the stolen sacred texts back to the priests.
After returning from Egypt Bagoas took power at the court in Susa and in the upper satrapies, while Mentor of Rhodes operated in the west of the Empire.
In 340 Philip of Macedonia attacked Perinthus and Byzantium on the European side of the Sea of Marmara and the Bosporus. Artaxerxes sent effective support to these cities, a move that later gave Philip an excuse to invade Asia Minor.
In 338 Bagoas had Artaxerxes and all but one of his sons murdered after losing some of his influence at the court. The Emperor himself was poisoned by his doctor. Bagoas then placed the surviving son Arses on the throne, but the new Emperor wasn't as easy to control as Bagoas had expected. In 336 Bagoas had Arses murdered and placed Darius III on the throne.
Darius soon turned out to more independently-minded than Bagoas had hoped. He attempted to poison Darius, but the Emperor was pre-warned, and Bagoas was forced to drink his own poison.