Dolorous Stroke

The Dolorous Stroke is a trope in Arthurian legend and some other stories of Celtic origin.In its fullest form, it concerns the Fisher King, 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.
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In Malory, the blow dealt to King Pellam by Balin of the Two Swords, reducing the region of Logres to a wasteland.

[Arthurian] Blow by which Balin wounds Pellam with the Holy Lance. This is the reason, in the Suite du Merlin, for the reduction of Logres to the Wasteland. This is divine judgment for the sacrilege of using the Lance as a weapon. Malory also adapts this story. The wounded king is himself ill for many years until cured by Galahad.