The two Augusti and two Caesars of Diocletian's tetrarchy have been commilitones, originating from the Balkanic provinces. They were chosen by Diocletian an the basis of friendship that was corroborated by family connections. Although these connections were changed partly because of invidia, Diocletian achieved a remarkable success through his system which was tightly connected with the possible oracle of a celtic sibyl. She said that Diocletian would became emperor if he slayed the wild boar. As Diocletian killed Flavius Aper (= boar), the oracle came true. The only representation of the boar slaying that relates to Diocletian is an inscribed tegula with such a representaion found in Intercisa.