The Fisher King is featured in the story "
Perceval".
In Chretien de Troyes' "Perceval", the Fisher King is immobile because he was injured in the leg with a lance. He used to be the protector of the lands near him, but because of his injury the lands have gotten into bad shape (see The Golden Bough). The reason he is called "the Fisher King" is because he goes fishing. He is also the holder of a few special objects, amongst which are a grail and a lance (the meaning of them is pretty obvious, but not stated by Chretien).