 Under Emperor Alexios I Komnenos he held the offices of head justice and private secretary ("protasēkrētis") to the emperor, but after Alexios' death, he retired to the monastery on the Island of Hagia Glykeria, (Incir Ada, in the Aegean Sea), where he spent the rest of his life writing books.His most important work, "Extracts of History" (, ), in eighteen books, extends from the creation of the world to the death of Alexius (1118).The earlier part is largely drawn from Josephus; for Roman history he chiefly followed Cassius Dio up to the early third century.