Ysbaddaden Chief Giant appears in the story, Culhwch and Olwen. He is described as the bad-tempered, powerful ruler of the giants, who puts all of his daughter's suitors to severe tests.
Ysbaddaden's temper leads him to violent acts, which include the slaughter of his own followers' children. He attacks Culhwch and his party when they arrive and curses the warriors for wounding him with the poisoned spears he initially threw at them. He does, however, tamely allow himself to be killed once his quest is acheived, and he is obviously highly protective of his daughter, who is not as harshly treated as his retainers.
The Mabinogion