In its fullest form, it concerns the Fisher King (King Pellehan), the guardian of the Holy Grail, who falls into sin and consequently suffers a wound from a mystical weapon (often the Spear of Destiny). He becomes the Maimed King, and his kingdom suffers similarly, becoming the Wasteland: neither will be healed until the successful completion of the Grail Quest.
The stroke is usually described as being in the king's thighs: this has been taken as a euphemism for the genitals, which are explicitly stated to be the location of Anfortas' wound in Wolfram von Eschenbach's Parzival. In the Post-Vulgate Cycle, Thomas Malory's Le Morte d'Arthur, and later works based on those, the stroke is delivered by Sir Balin. He ignores an "unearthly voice" and strikes the king when he is deprived of his weapon and thinks his stroke is 'justified'.