Believed to be a son of King Merion, Mark's origins are shrouded in mystery. Breton legend makes him a son of Teudar Mawr, the King of Penwith. This is the evil King Mark of Cornwall, infamous for the ill-treatment of his nephew, Tristram. He may, however, have been dreadfully wronged in this episode of West Country history, for Tristram had become the lover of Mark's wife, the beautiful Iseult (or Isolde) of Ireland, and flaunted their relationship before the whole court (See below). It was little wonder that the two didn't get on. Mark apparently lived at Tintagel Castle & Castle Dore near Lantyan (Lancien in the 5th century).
Some say that, like Pinnochio, Mark had horse's ears: a fact that was revealed every time he had a hair-cut. To keep this secret, he therefore murdered each of his barbers. That is until a local man made a set of pipes from reeds growing on one of the barbers' graves. Whenever he played them, they would sing, "March ap Merion has horse's ears"! This story appears to hail from Wales, though, and may refer to a son of King Glywys of Glywysing (Glams), Merchwyn Wyllt (Marcianus Vesanus), King of Gorfynydd (Western Glams).
Mark ruled, not only in the West Country, but also in Brittany, possibly through claims as a descendant of Conan Meriadoc. It was to here that he retired after Iseult's death, as Prince of Poher in Eastern Cornouaille. He is mentioned by Gregory of Tours in his "History of the Franks", as well as in the Lives of Saints Samson & Pol de Léon. These records indicate that his full name was in fact Cono-mark, the same as his ancestor, Conomor. Being an ambitious man, he dreamt of uniting the whole of Brittany which was then a disjointed group of petty principalities. To this end, Mark invaded and conquered many of his neighbours' lands. He took the Kingdom of Domnonée by more nefarious means though. He supposedly murdered its king, Jonas, and married his widow. He was kind and generous to both her and her son, Judwal, until one day Mark's new wife dreamt that all the kings in Brittany paid homage to her son while he sat upon a mountain. The King was highly disturbed by this supremacy dream and plotted to kill them both. However, they escaped to St. Lunaire's monastery and the holy man sent them to King Childebert in Paris.
Later, King Mark set his sights on St. Triphine the daughter of King Waroc of Broërec. The prospective father-in-law was not keen on the idea, but was persuaded to let St. Gildas negotiate. Afraid of what Mark might do if his proposals were rejected, Gildas advised that the wedding go ahead. He would personally guarantee Triphine's safety, and gave her a holy silver ring to seal his promise.
At first the couple were happy together, but Mark changed when he discovered that Trephine was pregnant. He had once been warned that he would be killed by his own son. Fearing the worst, he again plotted his own wife's murder. Triphine, meantime, had noticed her ring had turned jet black and knew that her life was in danger. So, during the night, she crept down to the Royal crypt. She had heard gossip that it contained a secret passage out of the castle. But here she was greeted by six stone coffins, one empty and five full. To the Queen's horror, the ghosts of the dead immediately rose and revealed themselves to be Mark's previous wives! He had murdered each in turn, by poison, strangulation, fire, battery and drawing (as in hung, drawn & quartered). They gave Triphine the instruments of their destruction to help in her escape and she fled to the forest. Here she saw her father's hawk hunting overhead and called to it to take her ring home and summon help. Unfortunately, it was not long before Mark caught up with his wife. He found her hiding in a bramble bush, and coldly cut off her head.
Weroc, meanwhile, had received his daughter's ring and understood. He called for St. Gildas to fulfill his promise. Gildas travelled to Mark's court where the hawk guided him to Triphine's decapitated body. He could not believe the site that greeted his eyes, but calmed himself and prayed for his ward. Miraculously, her body began to move: it sat up, picked up her head and replaced it to its rightful position. Thus cured, Triphine returned to Broërec, where she gave birth to a son, Tremeur. The people rose against Mark, Prince Judwal was restored to Domnonée and Mark was outlawed from most of his lands. He returned to Britain, and Cerniw.
Years later, on a trip to Poher, he was riding through the same forest where he had murdered Triphine, when he came across some young lads playing. Asking one his name, he replied, "Tremeur, Sir". Certain this was his own son, Mark instantly drew his sword, decapitated the poor boy and rode off back to his castle. The little martyr, however, picked up his head and carried it after his father. On reaching the castle, the walls crumbled and fell, crushing Mark to death.
Generally considered legendary