: IS-ba-THA-den PEN-kaur
Welsh: lit. "Hawthorn the Giant Chief"
Father of Olwen and reluctant father-in-law of Culhwch in the Mabinogion's "Culhwch ac Olwen." He had a poison eye like the Irish Balor, and gave Culhwch an exhaustive series of tasks to perform in order to marry Olwen--so exhaustive, that Culhwch had to call on his uncle, King Arthur, and the Knights of the Round Table.
Ysbaddaden was killed by Culhwch's cousin Goreu ap Custennin, whose father was deposed by Ysbaddaden.