Tristan, representing the Sun, is born in Bretany, the southernmost site of the Celtic world. The south is the only place from which the sun shines at Midwinter in northern countries. When Tristan grows up, he reaches, as a young man, the court of his uncle, King Mark of Cornwall, which is situated at the center of the Celtic world (Wells does not form a part of the main story). Like the invigorated sun in Spring, Tristan then shows his prowess as a fighter and as a poet and musician. But the court belongs to King Mark, whose name denotes "horse" — an animal sacred to the sun. In fact the King, as a relative of Tristan, acts as the part of the hero who particularly represents the Sun God at his peek; and it is he who actually marries the representative of the Goddess of Nature as a young bride in the form of Isolde the Fair.

It is also Tristan's function, as his name, "born to sorrow", denotes, to be always wounded while fighting his rival and reach the point of death. In this story, however, Tristan plays a double part of the young Sun God as a lover of the Goddess, and of his own "weird," or "fate", as Graves calls him in his book The White Goddess, against whom he fights and by whom he is mortally wounded. In the story, however, Tristan never fights against King Mark himself, probably because the self identification here is too close.

The first rival Tristan fights is a messanger from Ireland, a nephew of Queen Isolde, young Isolde's mother. Tristan fights against him, kills him but receives poisonous wounds from his sword. He is forced to go to Ireland to get himself cured by the Queen there, and that is the next stage in Tristan's wanderings. In this story, Ireland also plays a double role: it is the northernmost place of the Celtic world, from which the Sun shines in Midsummer; but Midsummer is not only the peak of the Sun's rule over the world, it is also the point where he is killed by his rival and leaves the world of the living to go "west." Because Ireland also lies west of the main Celtic world, the place where the Sun sets in the evening and where the Land of the Dead is situated. Queen Isolde, then, is not only a Mother figure; she is also the Killer figure who causes the Sun to die. But the domain of the Underworld is also the place where all wisdoms and crafts lie, and the Queen is a mistress of these crafts and wisdom — in this case, particularly of medicine. It is no wonder, then, that Tristan's would-be Irish killer also heals him of his poisonous wounds.

The sad hero does not die at this stage. Instead, he takes the young bride, having fallen desperately in love with her, to her destined husband, the Sun King Mark. But occasionally, throughout the story, Tristan himself reverts to his initial function as the young Sun God. Isolde joins him, and the lovers spend some time on their own. One of the places where they find refuge is a forest, which is the realm of symbolic myth, outside human realistic habitation. Such episodes, though, cannot last, as Mark is Isolde's legitimate groom, according to the Nature myth, even before the advent of Christian morality. Acknowledging this fact, Tristan takes Isolde back to court and continues with his wanderings throughout the Celtic world.

But, while the myth is cyclic and never has a definite ending, the legend ends with the natural end of human life. Tristan goes back to Bretany, the place where he had been born, which symbolizes the Underworld for the Sun hero, the place where the sun goes in winter, which is the Kingdom of the Dead. In Bretany, Tristan meets and marries Isolde the White-Handed, who is called in the Icelandic balad Isolde the Black. Black is the colour of the Death goddess, and here the Black Isolde is Queen. Having been wounded again by a poisonous arrow, Tristan finally dies in agony, as befits the Sun God, who serves as sacrifice to the Goddess of Nature.