In most versions of the story of
Tristan and Iseult, King Mark of Cornwall is
Tristan's uncle. His sister is Tristan's mother,
Blancheflor (also known as Elizabeth or Isabelle). In some later versions he is related to Tristan's father,
Meliadus.
Peter Bartrum noted "In the older versions of the Tristan legend Mark was a sympathetic character and behaved honourably in spite of much frustration." : "King Mark slew the noble knight Sir Tristram as he sat harping before his lady la Belle Isolde."|alt=Illustration of Mark preparing to kill Tristan with a sword In the
Prose Tristan, Mark is the son of king
Felix and his character deteriorates from a sympathetic
cuckold to a villain; he rapes his niece and murders her when she produces his son, Meraugis. Mark also murders his brother, Prince Boudwin, and later kills Boudwin's vengeful teenage son Alisander (Alisuander, Alexander) the Orphan. In earlier variants of the story, Tristan dies in
Brittany far from Mark; in the Prose
Tristan, however, Tristan is mortally wounded by Mark while he plays the harp under a tree for Iseult. This version of Mark was popular in other medieval works, including the
Romance of Palamedes and
Thomas Malory's ''
Le Morte d'Arthur''. In these texts, Mark usually rules Cornwall from
Tintagel Castle, is often an enemy of Arthur's jester knight
Dinadan, and (as in the
Post-Vulgate Cycle) even destroys
Camelot after the
death of Arthur, allying himself with the pagan
Saxons and killing the archbishop. Some Post-Vulgate variants end with the death of Mark. In Micheau Gonnot's
Arthurian Compilation, he is ambushed by the sons of his baron Dinas, who tie him to a tree and leave him to be eaten alive by a bear. Malory's version says that Alisander's son eventually avenges his father and grandfather, presumably by killing Mark.
Horse ears Mark has become associated with a
Celtic variant of the story of
Midas and his donkey ears from
Greek mythology, due to a pun on
marc (a Celtic word for "horse").
John Rhys recorded a Welsh tale similar to the simpler Breton version. An embellished 1905 version, collected by
Yann ar Floc'h, blends the legend of
Ys with the premise that Mark was condemned by
Gradlon's daughter (or
Dahut). ==Modern culture==