Pagan has been identified as a member of that faction of the Bulgarian aristocracy, which sought to establish peaceful relations with the Byzantine Empire. After ascending the throne following the murder of his predecessor Toktu, Pagan set out together with his court to attend negotiations with Emperor Constantine V Kopronymos somewhere in Thrace. In the heated talks the emperor represented himself as intent on keeping the peace in Bulgaria and upbraided the Bulgarians for their anarchy, and for deposing their former ruler Sabin, who lived as a refugee at the imperial court. The emperor nevertheless agreed to make peace, and Pagan returned home.
At this point Constantine V suddenly invaded Bulgaria and managed to penetrate across the mountains into the core area of the Bulgarian state, setting afire some settlements around the Bulgarian capital Pliska. Although Constantine V did not follow up his relatively successful invasion and returned home, Pagan faced the wrath of his subjects who accused him of credulity and inability to oppose the enemy. The monarch fled in the direction of Varna, but was murdered by his servants.
The 17th century Volga Bulgar compilation Ja'far Tarikh (a work of disputed authenticity) represents Boyan (i.e., Pagan) as the son of the former ruler Bunek (i.e., Vinekh), and credits him with the expulsion of Sain (i.e., Sabin).