Zonaras

Ioannes Zonaras was a Byzantine historian and canonist who flourished in the early twelfth century AD. He held the offices of commander of the bodyguard (drungarios tēs viglas) and private secretary (prōtasēkrētis) to the emperor before retiring to a monastery on an island in the Sea of Marmara, where he wrote his major works.

His Epitome of Histories (Epitomē Historiōn) covers the history of the world from creation to 1118 AD. For the Roman period, it is invaluable because Zonaras used sources that are now lost — particularly the books of Cassius Dio that survive only in fragments. For Dio's account of the late Republic and early Empire, Zonaras is often our best witness to what the original text said. He also wrote commentaries on canon law and liturgical poetry. His historical work is a compilation rather than original composition, but a remarkably useful one.