Complex sentence: Michael fled, leaving his treasury to a certain Michael Ivac, probably a son of Ivac, a general under Samuil of Bulgaria, who promptly turned over the bulk of the treasury to Peter outside the city.
Split into simpler sentences: Michael fled, leaving his treasury to a certain Michael Ivac. The latter, who was probably a son of Ivac, a general under Samuil of Bulgaria, promptly turned over the bulk of the treasury to Peter outside the city.