The Byzantine Empire
Alexius V (1205)
It was this Alexius, Alexius V Ducas Murzuphlus, who ruled the city when the Crusaders took it by assault on April 13, 1204. He fled and joined his father-in-law at Mosynopolis. Alexius III had him blinded, for he was now a rival claimant to the throne. Murzuphlus was later captured by the Latins and was executed by being hurled from the column of Theodosius in Constantinople. Alexius III was captured by Boniface of Montferrat, was ransomed by Michael I of Epirus, and ended his days in a monastery in Nicaea.
The house of Comnenus was gone. The house of Angelus had collapsed in ruins. The hated Latins ruled Constantinople, but there was no shortage of Greek claimaints to the Byzantine throne. The history of Byzantium now bifurcates for about fifty years, with the Latins ruling the city and much of Greece, while the Greeks build an sort of counter-empire in northern Asia Minor. The two are intertwined, but I'll concentrate here on the Greek side of the story.