Phostis was the name given to the Avtokrator Krispos' first-born son and heir to the Videssian throne. He was the older brother to Evripos and Katakolon. The boy was named for Krispos' father. Krispos had doubts about who the boy's biological father was, as Dara the empress and mother became pregnant with the child while her first husband, Anthimos III, was still alive. Phostis was named Krispos' co-avtokrator while still an infant.