John III Doukas Vatatzes was Emperor of Nicaea from 1222 to 1254. He was succeeded by his son, known as Theodore II Laskaris.
Born to an aristocratic Byzantine family, he married Irene, daughter of Theodore I Lascaris, emperor of Nicaea, becoming emperor on Theodore’s death.
By acquiring territory, encouraging economic growth, and supporting a cultural revival from his capital at Nicaea (modern Iznik, Turkey), John paved the way for the recovery of Constantinople from the Latin emperors and the reestablishment of the Byzantine Empire.
He was successful in maintaining generally peaceful relations with his most powerful neighbours, Bulgaria and the Sultanate of Rum, and his network of diplomatic relations extended to the Holy Roman Empire and the Papacy, while his armed forces included Frankish mercenaries.
Depicted here is a Gold hypopyon of John III Vatatzes. It depicts the Emperor standing facing, holding labarum and being crowned by Mary to right.
Image Source: https://en.wikipedia.org