Nennius of Britian

Nennius was a prince in Britian when Julius Caesar attempted to invade several times during the 50s BCE. He died after using Crocea Mors (also known as Yellow Death) to successfully drive Ceasar away. In the early 21st century, his corpse was brought back to life by the head of Cacus. 

History
In 1136, Nennius was chronicled in Geoffrey of Monmouth's History of the Kings of Britain.