The nomadic Avars subjugated the Gepids in 568 and dominated the Carpathian Basin up until around 800. The Bulgars also established a powerful empire in the 670s which included Dobruja and other territories along the Lower Danube. Bulgaria officially adopted the Eastern Orthodox variant of Christianity in 864. An armed conflict between Bulgaria and the nomadic Hungarians forced the latter to depart from the Pontic steppes and began the conquest of the Carpathian Basin around 895. Their invasion gave rise to the earliest reference, recorded some centuries later in the "Gesta Hungarorum", to a polity ruled by a Romanian duke named Gelou. The same source also makes mention of the presence of the Székelys in Crişana around 895. The first contemporaneous references to Romanianswho used to be known as Vlachsin the regions now forming Romania were recorded in the 12th and 13th centuries. References to Vlachs inhabiting the lands to the south of the Lower Danube abound in the same period.