Gorboduc the Fiend

Sir Gorboduc of Medbourne was a fiend born to the daughter of Sir Staterius of Medbourne and an incubus.
He aged rapidly, being fully-grown by age five. Known for violent tendencies, he killed his grandfather at age nine and his bandits took control of the village.
In 497, at age eleven, he attempted to construct a magical tower known as the Serpent's Tower to serve as a leyline to the Faerie Realm, with the intention of impregnating more women with incubi and creating an army of fiends.
Later that year, Gorboduc was killed by Sir Alwyn of Oxenwood, aided by Helen of the Wells, Merlin the Magician, Mars of Winterbourne Stoke, Sir Edward of Upavon and Sir Drystan of Tilshead.