Page "Lancelot" Paragraph 26

Ultimately, Lancelot's affair with Guinevere is a destructive force, resulting in the death of Gawain's brothers and his two sons, the estrangement of Lancelot and Gawain, and Mordred's betrayal of King Arthur.

Upon hearing the news of Arthur's death, Lancelot finds that Guinevere has become a nun.