King Arthur followed ever after; for in his heart was bitter anger against the false nephew who had wrought woe upon him and all his realm.  At the last, when Mordred could flee no further, the two hosts were drawn up near the shore of the great western sea; and it was the Feast of the Holy Trinity.

That night, as King Arthur slept, he thought that Sir Gawain stood before him, looking just as he did in life, and said to him:  “My uncle and my King, God in his great love has suffered me to come unto you, to warn you that in no wise ye fight on the morrow; for if ye do, ye shall be slain, and with you the most part of the people on both sides.  Make ye, therefore, treaty for a month, and within that time, Sir Launcelot shall come to you with all his knights, and ye shall overthrow the traitor and all that hold with him.”  Therewith, Sir Gawain vanished.  Immediately, the King awoke and called to him the best and wisest of his knights, the two brethren, Sir Lucan the Butler and Sir Bedivere, and others, to whom he told his dream.  Then all were agreed that, on any terms whatsoever, a treaty should be made with Sir Mordred, even as Sir Gawain had said; and, with the dawn, messengers went to the camp of the enemy, to call Sir Mordred to a conference.  So it was determined that the meeting should take place in the sight of both armies, in an open space between the two camps, and that King Arthur and Mordred should each be accompanied by fourteen knights.  Little enough faith had either in the other, so when they set forth to the meeting, they bade their hosts join battle if ever they saw a sword drawn.  Thus they went to the conference.

Now as they talked, it befell that an adder, coming out of a bush hard by, stung a knight in the foot; and he, seeing the snake, drew his sword to kill it and thought no harm thereby.  But on the instant that the sword flashed, the trumpets blared on both sides and the two hosts rushed to battle.  Never was there fought a fight of such bitter enmity; for brother fought with brother, and comrade with comrade, and fiercely they cut and thrust, with many a bitter word between; while King Arthur himself, his heart hot within him, rode through and through the battle, seeking the traitor Mordred.  So they fought all day, till at last the evening fell.  Then Arthur, looking around him, saw of his valiant knights but two left, Sir Lucan and Sir Bedivere, and these sore wounded; and there, over against him, by a great heap of the dead, stood Sir Mordred, the cause of all this ruin.  Thereupon the King, his heart nigh broken with grief for the loss of his true knights, cried with a loud voice:  “Traitor! now is thy doom upon thee!” and with his spear gripped in both hands, he rushed upon Sir Mordred and smote him that the weapon stood out a fathom behind.  And Sir Mordred knew that he had his death-wound.  With all the might that he had, he thrust him up the spear to the haft and, with his sword, struck King Arthur upon the head, that the steel pierced the helmet and bit into the head; then he fell back, stark and dead.