A giant who possessed a magical sword, which was the only item that could kill him.
Obtaining this sword was the last of the tasks assigned to Culhwch by the giant Ysbaddaden, but it was the first to be accomplished. Culhwch and his party arrived at Wrnach’s hall during a feast, and Cei managed to gain entry by claiming to be a sword burnisher. Wrnach turned his sword over to Cei for polishing. After Cei shined the weapon, he thrust it into Wrnach’s chest and cut off his head. Culhwch and the warriors of Arthur then plundered Wrnach’s kingdom.