Celts in Transylvania arrived in northwestern Transylvania in around 400–350 BC as part of their great migration eastwards. When Celtic warriors first penetrated these territories, the group seem to have merged with the domestic population of early Dacians and assimilated many Hallstatt cultural traditions. The second half of the 4th century BC saw the Middle La Tène Celtic culture emerge in north-western and central Dacia, a development reflected especially in burials of the period. Celtic artifacts dating to this time have been discovered at Turdaş, Haţeg and Mediaş in modern-day Romania. By 1976, the number of Celtic sites found in Transylvania had reached
History of Transylvania organization of the Transylvanian Catholic episcopacy (with Gyulafehérvár as its seat), which was finished in 1009 when the bishop of Ostia (as papal legate) visited Stephen and they approved diocesan divisions and boundaries. In 1018 Stephen defeated Ahtum, ruler of the country around the lower Mureș River. According to the "Chronicon Pictum", Stephen I also defeated the legendary Kean (a ruler in southern Transylvania of Bulgarians and Slavs). During the 12th century, the Székelys were brought to eastern and southeastern Transylvania as border guards. In the 12th and 13th centuries, the areas in the south and northeast were settled by