Besides this linguistic, had the Celts also a political unity over their great "empire," under one head? Such a unity certainly did not prevail from Ireland to the Balkan peninsula, but it prevailed over a large part of the Celtic area. Livy, following Timagenes, who perhaps cited a lost Celtic epos, speaks of king Ambicatus ruling over the Celts from Spain to Germany, and sending his sister's sons, Bellovesus and Segovesus, with many followers, to found new colonies in Italy and the Hercynian forest.[46] Mythical as this may be, it suggests the hegemony of one tribe or one chief over other tribes and chiefs, for Livy says that the sovereign power rested with the Bituriges who appointed the king of Celticum, viz. Ambicatus. Some such unity is necessary to explain Celtic power in the ancient world, and it was made possible by unity of race or at least of the congeries of Celticised peoples, by religious solidarity, and probably by regular gatherings of all the kings or chiefs. If the Druids were a Celtic priesthood at this time, or already formed a corporation as they did later in Gaul, they must have endeavoured to form and preserve such a unity. And if it was never so compact as Livy's words suggest, it must have been regarded as an ideal by the Celts or by their poets, Ambicatus serving as a central figure round which the ideas of empire crystallised. The hegemony existed in Gaul, where the Arverni and their king claimed power over the other tribes, and where the Romans tried to weaken the Celtic unity by opposing to them the Aedni.[47] In Belgium the hegemony was in the hands of the Suessiones, to whose king Belgic tribes in Britain submitted.[48] In Ireland the "high king" was supreme over other smaller kings, and in Galatia the unity of the tribes was preserved by a council with regular assemblies.[49]