Hogalen Tudwal Tudclyd is one of the Thirteen Treasures of the Island of Britain, also known as The Whetstone of Tudwal Tudclyd (sometimes Tudglyd or Tudclud). If a brave man sharpened his sword on the whetstone and then injured his enemy in battle, the wound would always be fatal. However, if a cowardly man sharpened his sword on it, no additional harm would come to his enemies.
