Sir Turquine was the son of Mitrides (or Aupatris) and the brother of Sir Caradoc of the Dolorous Tower. Like his brother, he enjoyed defeating Knights of the Round Table in battle and throwing them into prison at his Northern manor in the Impenetrable Forest (traditionally claimed by both Manchester and Tamworth).

For twelve years, he kept a bronze bowl hanging from a lone tree by an important river crossing and passing knights would use it as a bell to summon him into combat with them. Turquine would always win, of course. The knight would be incarcerated for the duration and his shield hung on the tree as a warning to others. He amassed quite a collection until he made Sir Ector de Maris one of his inmates and his brother, Sir Lancelot, came looking for him. Ector, in fact, fought so well that Turquine had offered to set him free, if he agreed to stay at the manor and keep him company. The Knight of the Marshes naturally refused and was thrown into a dismal little pit with sixty-four others and was beaten with thorns on a daily basis.

When Lancelot eventually discovered his brother's gaoler, he engaged him in single combat for over two hours. Turquine was so impressed by his unknown assailant's military skill that he offered to end the fight and release all his prisoners for him, with the one proviso that he was not the knight whom he hated above all others. This knight, of course, turned out to be Lancelot, because he had killed Turquine's brother. The two therefore fought on until Lancelot finally struck Turquine down.