Agravaine

Agravaine was a Knight of the Round Table. He, Galahad, Bedevere and Gawain were Merlin once sent on a four-day journey to slay the Morch'aliach entity in its cave with the help of Merlin's own sister and fellow wizard, Ganeida. After they camped out near the cave's entrance, Agravaine, going against the other knights' wisdom, caused a rock slide in the night which sealed the creature in its lair until the 21st century. He was heavily reprimanded by Gawain, the nominal leader of the expedition, for this rash action and its unchivalrous nature. (PROSE: A Honeycomb of Souls)