Hezul is one of the Twelve Crusaders, possesses the title of Black Knight, is the original wielder of the Mystletainn, and is the founder of Agustria. His youngest daughter had major holy blood and was married off to the Nordion house, "locking" the major blood in the Nordion lineage. His direct descendants, who formed the royal family, have only minor holy blood: they reached an agrement with House Nordion, giving them Mystletainn in return for their eternal loyalty.
Hezul is a possible reference to Hod, the blind god of Norse mythology. He accidently killed his brother with the Mystletainn (mistletoe).