Eastern Emperor Leo V is murdered in a church of the Great Palace of Constantinople by followers of Michael II.

Leo V the Armenian
Leo V the Armenian was the Byzantine emperor from 813 to 820. He is chiefly remembered for ending the decade-long war with the Bulgars, as well as initiating the second period of Byzantine iconoclasm.
Church of the Virgin of the Pharos
The Church of the Virgin of the Pharos was a Byzantine chapel built in the southern part of the Great Palace of Constantinople, and named after the tower of the lighthouse (pharos) that stood next to it. It housed one of the most important collections of Christian relics in the city, and functioned as the chief palatine chapel of the Byzantine emperors.
December 25
December 25 is the 359th day of the year in the Gregorian calendar; six days remain until the end of the year.