One day, as the dawn broke, a sentinel ran from the tower through the halls crying: "Lords, you have slept too long; rise, for an assault is on."
And knights and burgesses armed, and ran to the walls, and saw helmets shining on the plain, and pennons streaming crimson, like flames, and all the host of Riol in its array. Then the Duke and Kaherdin deployed their horsemen before the gates, and from a bow-length off they stooped, and spurred and charged, and they put their lances down together and the arrows fell on them like April rain.
Now Tristan had armed himself among the last of those the sentinel had roused, and he laced his shoes of steel, and put on his mail, and his spurs of gold, his hauberk, and his helm over the gorget, and he mounted and spurred, with shield on breast, crying: "Carhaix!"
And as he came, he saw Duke Riol charging, rein free, at Kaherdin, but Tristan came in between. So they met, Tristan and Duke Riol. And at the shock, Tristan's lance shivered, but Riol's lance struck Tristan's horse just where the breast-piece runs, and laid it on the field.
But Tristan, standing, drew his sword, his burnished sword, and said: "Coward! Here is death ready for the man that strikes the horse before the rider."
But Riol answered: "I think you have lied, my lord!"
And he charged him.
And as he passed, Tristan let fall his sword so heavily upon his helm that he carried away the crest and the nasal, but the sword slipped on the mailed shoulder, and glanced on the horse, and killed it, so that of force Duke Riol must slip the stirrup and leap and feel the ground. Then Riol too was on his feet, and they both fought hard in their broken mail, their 'scutcheons torn and their helmets loosened and lashing with their dented swords, till Tristan struck Riol just where the helmet buckles, and it yielded and the blow was struck so hard that the baron fell on hands and knees; but when he had risen again, Tristan struck him down once more with a blow that split the helm, and it split the headpiece too, and touched the skull; then Riol cried mercy and begged his life, and Tristan took his sword.
So he promised to enter Duke Hoël's keep and to swear homage again, and to restore what he had wasted; and by his order the battle ceased, and his host went off discomfited.
Now when the victors were returned Kaherdin said to his father: "Sire, keep you Tristan. There is no better knight, and your land has need of such courage."