John IV (John Lascaris)lăsˈkərĭs, b. c.1250, d. after 1273, Byzantine emperor of Nicaea (1258–61), son and successor (under a regency) of Theodore II and last of the Lascarids. Michael Palaeologus (later Michael VIII) overthrew the regency and in 1259 was crowned coemperor. He postponed John's coronation and in 1261 had the boy blinded and imprisoned. It is possible that John escaped from his fortress and went (c.1273) to the court of Charles of Anjou.
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