John reports on his conduct: "He built vessels by means of which he could visit all the cities of Egypt with pleasure and delight.
And by reason of this command he became more and more presumptuous, and made all the troops submit to his orders, and led a fearless life.
And when men of high or low degree came to him from the emperor, he let them remain at the door and did not admit them for a long time.
A possible interpretation is that Aristomachus' proper position was in Upper Egypt, close to Nubia, perhaps as the military governor of Thebaid, but then the man attempted to illegally extend his authority.
"Aristomachus ... proceeded to the city of Alexandria with only a few attendants; for he was not aware of the treacherous device they had prepared against him.
And when the patriarch and Andrew saw him, they were delighted, and got ready a light ship on the sea close at hand to the Church of St. Mark the Evangelist.
And thereupon Andrew made a signal to his attendants and to the soldiers to seize Aristomachus and to cast him into the vessel.
And immediately they seized him, and, bearing him on their shoulders, cast him into the vessel, without his being aware (of the reason), and loosing thence they set sail to go to the emperor.
The text narrates "the empress Constantina appointed him controller of all her house and loaded him with honours, until he was second only in rank to the emperor, and he became a very great personage in the city of Byzantium".
And the emperor became hostile forthwith to Aristomachus, and he robbed him of every hope, and exposed him to numerous humiliations, and sent him in exile to the island of Gaul where he had to remain till he died.