By 48 BCE, Damastes was employed by Apollodorus, a spymaster and ally of Cleopatra. At one point, he was entrusted with a scroll meant for the Roman general Pompey, with whom Cleopatra desired an alliance. When Apollodorus' ship was attacked near Kanopos, Damastes chose to hide the scroll aboard the ship. However, the ship sank, and Damastes was captured. At the behest of Apollodorus, the Medjay Bayek of Siwa rescued Damastes and recovered the scroll.
Eventually, Damastes found service aboard a trireme captained by Phoxidas, a mercenary-turned-admiral to Cleopatra. Serving as a shield boy to Phoxidas, Damastes showed great loyalty and admiration towards him, and sailed with him and Aya, Bayek's wife. Damastes was present when Aya and Phoxidas delivered a bribe to Pompey in order to win the general's allegiance and when Cleopatra herself was escorted to Alexandria aboard the trireme, struck with awe at seeing the woman he considered a goddess. Damastes also participated in a battle against Roman ships in the Tyrrhenian Sea in 46 BCE.