Uther Pendragon

Uther Pendragon vows to deliver the child to Merlin.

King Uther Pendragon was the father of Arthur. He was the brother of Ambrosius whom he succeeded as King of Britain. Falling in love with Igraine, he went to war 
with her husband, Gorlois. During the war, Merlin magically made Uther assume the likeness of Gorlois and in this guise he visited Igraine and became the father of Arthur. When Gorlois died, Uther married Igraine. He died in battle and was supposedly buried at Stonehenge.

The Prose Tristan says Uther was once in love with the wife of Argan who defeated him and made him build a castle. ThePetit Brut tells how he fought a dragon-serpent in Westmorland (now part of Cumbria). Henry of Huntingdon calls him Arthur's brother while a Cumbrian legend makes him a giant. In Cumbria, he is said to have founded his kingdom in Mallerstang and to have tried to divert the River Eden to make a moat around his castle. 

It has been suggested that Uther is a chimerical character created by a misunderstanding of the Welsh phrase: Arthur mab Uther, which was taken to mean 'Arthur son of Uther' but actually means 'Arthur, terrible son'. However, there is evidence for independent tradition regarding Uther.