Mordred was so angry to see King Arthur remounted that he almost took leave of his senses; he charged at Sir Yvain, holding his sword in both hands. The blow was heavy and came from above, and it split Sir Yvain's helmet and steel coif down to his teeth; Mordred struck him down dead, and that was a terrible tragedy, for at the time Yvain was considered to be one of the best knights and most valiant men in the world.

The Vulgate Cycle