Vortigern

Vortigern is the brother of Uther Pendragon and uncle to his two children, King Arthur and Morgan le Fay. Vortigern, having drank the blood of the white dragon and become the very avatar of Britain, is a monster who even the powerful Knights of the Round Table could not imagine. Covered in darkness, he is a "hole in the world" that acts as a devourer of holy swords, the darkness growing thicker the holier its adversary. One attack is enough to incinerate a retinue of elite knights and bring Gawain and Artoria to the brink of defeat. (Source: TYPE-MOON Wiki)