succeeds him. The text identifies the poisoner as Eopa. Judgements tend to vary wildly of the value of Geoffrey as both a historian and a literary storyteller. He has been praised for giving us detailed information about an otherwise obscure period and possibly preserving information from lost sources, and condemned for an excessive use of artistic licence and possibly inventing stories wholecloth. According to Frank D. Reno, whenever Geoffrey uses extant sources, the details in the text tend to be accurate. Assuming that he was also using sources lost to us, it may be difficult to decide which details are truthful. Reno suggests that "individual judgements" have to be made about various elements of his narrative. Geoffrey changed the word "Aurelianus" to "Aurelius", which is the name of a Roman gens. Geoffrey retains the story of Emrys and the dragons from Nennius, but identifies the figure with Merlin. Merlin is Geoffrey's version of a historical figure known as Myrddin Wyllt. Myrddin is only mentioned once in the Annales Cambriae, at an entry dated to 573. The name of Merlin is given in Latin as Ambrosius Merlinus. "Merlinus" may have been intended as the agnomen of a Roman or Romano-British individual like Ambrosius. Elements of Ambrosius Aurelianus, the traditional warrior king, are used by Geoffrey for other characters. Ambrosius' supposed supernatural powers are passed to Merlin. Geoffrey's Aurelius Ambrosius rises to the throne but dies early, passing the throne to a previously unknown brother called Uther Pendragon. The role of warrior king is shared by Uther and his son Arthur. Geoffrey also uses the character Gloiu, father of Vitalinus/Vitolinus, derived from Nennius. He names this character as a son of Claudius and appointed by his father as Duke of the Welsh. His predecessor as Duke is called Arvirargus. Assuming that Claudius and Arvirargus are supposed to be contemporaries, then this Claudius is the Roman emperor Claudius I (reigned 41–54). It seems unlikely that Claudius would have living grandsons in the 5th century, four centuries following his death. Reno suggests that Claudius II (reigned 268–270) would be a more likely "Claudius" to have living descendants in the 5th century. Geoffrey for the first time gives a genealogy of Ambrosius. He is supposedly a paternal nephew of , King of Brittany, son of Constantine and an unnamed Briton noblewoman, adoptive grandson (on his mother's side) of Guthelinus/Vitalinus, Bishop of London, younger brother of