Guinevere appears in Geoffrey of Monmouth's "Historia Regum Britanniae", a pseudo-historical chronicle of British history from the mid 12th-century, in which she is seduced by Mordred during his rebellion against King Arthur. In a later medieval Arthurian romance tradition from France, a prominent story arc is Guinevere's tragic love affair with her husband's chief knight and friend, Lancelot, indirectly causing the death of Arthur and many others and the downfall of the kingdom. Such motif first appeared in a nascent form in Chrétien de Troyes's poem "Lancelot" prior to its vast expansion in the 13th-century prose cycle "Lancelot-Grail", from which it featured as a major plotline in Sir Thomas Malory's seminal English compilation "Le Morte d'Arthur". Guinevere has continued to be a popular character in modern adaptations of the legend, usually in relation with Lancelot.