Reference: Rietstap's Armorial [1]
Flag depicting the attributed dynastic Arms of the Doukas [Ducas] family (1204-1359). A family allegedly descended from a cousin of the Roman Emperor Constantine I who had migrated to Constantinople in the 4th century. The family or families using this surname supplied several rulers to the Byzantine Empire. A branch of the family, the Komnenos-Doukas, founded and ruled the Despotate of Epiros for over 150 years (1204-1359).

Azure, a cross Argent.
Own work
Dragases (talk)