Agravaine
Knight whose exposure of Launcelot and Guinevere destroyed the Round Table.
Agravaine is a knight of the Round Table attested in Le Morte d'Arthur (27 citations across 13 chapters) and Sir Gawain and the Green Knight (2 citations). He is the brother of Gawain and Mordred, nephew to King Arthur, and the chief architect of Launcelot's exposure and downfall. Where Mordred provides cunning, Agravaine provides relentless, public aggression -- he is the one who forces the crisis that destroys the Round Table.
The two sources construct Agravaine differently. Sir Gawain and the Green Knight gives him the epithet "a la dure main" (of the hard hand), noting that he "sat on Guinevere's other side" at the feast, and that both he and Gawain "were the king's sister's sons" (Sir Gawain and the Green Knight, Part I). The poem's editor observed that this French epithet "indicates a French source at the root of this story" (Sir Gawain and the Green Knight, Part IV), placing Agravaine within the continental Arthurian tradition even in this most English of texts.
In Le Morte d'Arthur, Agravaine is defined entirely by his campaign to expose Launcelot and Guinevere. Early in the text he appears in minor roles -- wedded to "Dame Lionesse's niece, a fair lady, her name was Dame Laurel" (Le Morte d'Arthur, Book VII, Ch. XXXV), and overthrown by Breuse Saunce Pite alongside Mordred (Le Morte d'Arthur, Book X, Ch. XXV). But the climactic narrative arc begins when Launcelot himself identifies the threat: "there be many men speak of our love in this court, and have you and me greatly in await, as Sir Agravaine and Sir Mordred" (Le Morte d'Arthur, Book XVIII, Ch. I).
The confrontation scene is Agravaine's defining moment. He speaks "openly, and not in no counsel, that many knights might hear it: I marvel that we all be not ashamed both to see and to know how Sir Launcelot lieth daily and nightly by the queen" (Le Morte d'Arthur, Book XX, Ch. I). Gawain's warnings are explicit and prescient -- "ye must remember how ofttimes Sir Launcelot hath rescued the king and the queen" (Le Morte d'Arthur, Book XX, Ch. I), and Launcelot had rescued Agravaine himself "and threescore and two, from Sir Turquin" (Le Morte d'Arthur, Book XX, Ch. I). But Agravaine is unmoved: "I will lain it no longer" (Le Morte d'Arthur, Book XX, Ch. I).
Having secured Arthur's licence to act, Agravaine and Mordred assembled twelve knights and trapped Launcelot in the queen's chamber, crying "Traitor-knight, Sir Launcelot du Lake, now art thou taken" (Le Morte d'Arthur, Book XX, Ch. III). The cry "Traitor-knight, come out of the queen's chamber" was repeated three times in the narrative (Le Morte d'Arthur, Book XX, Chs. III, IV), building toward the combat in which Launcelot killed Agravaine and all twelve confederates. Launcelot himself acknowledged the consequences: "I have slain this night these knights... as is Sir Agravaine Sir Gawaine's brother, and at the least twelve of his fellows" (Le Morte d'Arthur, Book XX, Ch. V).
Gawain's epitaph for his brother is damning: "they are the causers of their own death; for ofttimes I warned my brother Sir Agravaine, and I told him the perils the which be now fallen" (Le Morte d'Arthur, Book XX, Ch. VII). Yet Gawain's grief for his brother ultimately drives his own implacable pursuit of Launcelot -- Agravaine's death becomes the wound that cannot heal.