Also called Beaudous and Carduino, Sir Guinglain was Sir Gawain's eldest son by a fairy named Blanchemal. The lady raised her son in ignorance of his heritage; so when he appeared at the Court of King Arthur, he became known as Le Bel Inconnu - the “Fair Unknown”. Arthur sent him on a quest to restore the city of Snowdon (possibly Caernarfon) for Esmeree the Blonde, the Queen of Wales, after it had been laid waste by a pair of sorcerers.

The Queen’s Lady-in-Waiting messengeress, named Helie, was disgusted to be returning home with such an inexperienced youth as her champion. However, the Unknown Knight soon changed her mind about him when he was triumphant in a number of adventures en route. He overcame the arrogant Sir Bleoberis; he rescued the Lady Clarie from a pair of giants; he defeated three attackers and won a sparrowhawk tournament. Defeating the Guardian of the Golden Isle, he fell in love with his fairy mistress, the Maiden with the White Hands. The two wished to marry, but the knight with no name was obliged to sneak away to complete his quest. Arriving at Snowdon, the two sorcerers were soon defeated, but Sir Guinglain had to overcome natural revulsion and kiss the snake into which the Queen had been transformed. The wicked spell was thus broken and the Esmeree returned. She wished to marry her saviour, but he hurried back to the Maiden with the White Hands instead. She reluctantly accepted him back and revealed his real name. But Sir Guinglain could not resist the joust meetings and the fairy finally jilted him when he went off to the tournament at Maiden’s Castle. He eventually ended up with Queen Esmeree after all.

Sir Tristram first came to the notice of his uncle, King Mark of Cornwall, whilst jousting with Sir Guinglain at Tintagel. Guinglain’s horse was killed from under him and Mark replaced it in order to discover his opponent’s identity. Guinglain became a Knight of the Round Table and, with his brothers, Sirs Florence and Lovell, helped in the attempt in entrap Sir Lancelot and Queen Guinevere in flagrante delicto. Lancelot killed all three for their trouble.