Culwich (or Culhwch) is a cousin of King Arthur and very famous for the story of Culwich and Olwen.
Culwich was born in a pig-run because his mad mother, the queen, was frightened into labor by the hogs. She died soon after naming the boy Culhwich. His father remarried, and Culhwich's stepmother wants him to marry her daughter but he refuses.
Angry, she curses him so that he can marry no one but the beautiful Olwen. Olwen's father, Ysbaddaden, is a vicious giant who will die if his daughter marries, so he requires Culhwich to complete a number of impossible tasks, the most prominent of which being Culhwich's gaining of his cousin Arthur's military assistance, and the hunting of the wild boar, Ysgithyrwyn.
In Brittany, Arthur and his hound Caval hunted Ysgithyrwyn and split his head to take his tusk.
With Arthur's help, Culhwich completes the majority of the tasks and marries Olwen.
Culwich is also the name of one of the domains in Kingdoms of Camelot.