Trahern
Trahern is a legendary King of the Britons in Geoffrey of Monmouth's fictional "Historia Regum Britanniae" . 
<triplet> Trahern <subj> Historia Regum Britanniae <obj> present in work <triplet> Geoffrey of Monmouth <subj> Historia Regum Britanniae <obj> notable work <triplet> Historia Regum Britanniae <subj> Geoffrey of Monmouth <obj> author