Priscus was born between 410 and 420 AD in Panium (or Panion), Thrace. He joined in 448/449 AD the Roman embassy, led by Maximinus and speaking on behalf of Emperor Theodosius II, on a diplomatic mission to the court of Attila the Hun. While he was there, Priscus met and spoke with a Greek trader dressed in Hunnic clothes who was captured in around 441–442 AD when the Huns pillaged the city of Viminacium in modern Serbia. The trader then told Priscus that he was a slave of a Hunnic nobleman named Onegesius, but got his freedom and chose to live among the Huns. Priscus finally had a debate with the Greek defector about life and justice in both the Roman Empire and in barbarian kingdoms.