Никифор Григора
According to modern historians, "For Gediminas and Algirdas, retention of paganism provided a useful diplomatic tool and weapon ... that allowed them to use promises of conversion as a means of preserving their power and independence". Hermann von Wartberge and Jan Długosz described Algirdas as a pagan until his death in 1377. Contemporary Byzantine accounts support the Western sources; Patriarch Neilos described Algirdas as "fire-worshipping prince" and another patriarch, Philotheos, excommunicated all Ruthenian noblemen who helped the "impious" Algirdas. His pagan beliefs were also mentioned in 14th-century Byzantine historian Nicephorus Gregoras' accounts.