A few months after his arrival in Asia, Xerxes was assassinated (B.C. 465), and was after a short interval succeeded by Artaxerxes. Various adventures are told of Themistocles before he reached the residence of the Persian king. On his arrival he sent him a letter, in which he acknowledged the evils he had inflicted upon his predecessor; but at the same time claimed the merit of having saved him from destruction by his timely advice. He added that his present exile was only the consequence of his great zeal for the interests of the king of Persia. He did not ask for an immediate interview with the king, as he was yet unacquainted with the language and the manners of the Persians, to acquire which he requested a year's time. During this period he applied himself so zealously and with such success to these studies that at the close of the year, when he was presented to the king, he is said to have excited the jealousy of the courtiers, and was most kindly received by the king, to whom he held out prospects of conquering Greece by his assistance. The king became so attached to him, that Themistocles was always in his company.
But death overtook him at the age of sixty-five, before any of his plans were carried into effect. Most of the ancient writers state that he put an end to his life by poison, or according to another strange story, by drinking the blood of a bull, because he despaired of being able to fulfil his promises to the king. The motive for his suicide is very questionable. Reflection on his past life and upon the glory of his former rivals at Athens, are much more likely to have rendered him dissatisfied with life. Before he took the poison he is said to have requested his friends to convey his remains secretly to Attica, and in later times a tomb which was believed to contain them existed in Piræus. In the market-place of Magnesia a splendid monument was erected to his memory, and his descendants in that place continued to be distinguished by certain privileges down to the time of Plutarch.