Throughout his early years, Kephalon had longed to perform at the theater in Argos. However, his dream was never fulfilled as no one was willing to cast him in their plays. He soon exacted his revenge by killing those who rejected his performances and took up the job of being a mercenary.
Around 422 BCE, Kephalon was hired by the magi of the Order of the Storm Phila to hunt down the misthios Kassandra. He and another mercenary Proktos the Moon King were sent to patrol Boura located southwest of Patrai. Later, Proktos and Kephalon were eliminated by Kassandra herself.